Crp.211 Theory

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CRP 211 Applied Physiologies for Horticultural Crops 1+1

Course Teacher: Dr. K. Subburamu

Theory

Growth –differentiation- Development –definitions- types – pattern of growth –

determinate – indeterminate – allometric – growth. Growth Parameter – analysis – NAR

– RGR – CGR – harvest index – partitioning efficiency. Growth – regulators –

classification – role of PGRs in horticultural crops. PGRs application in fruits –

vegetables. PGRs application in Spices and plantation crops – flowers. PGRs for

propagation. Senescence – mechanism of senescence – control of senescence by PGRs.Role of PGRs in Post harvest physiology. Nutrio Physiology – importance of Macro –

Micro elements-essentiality –mode of translocation. Concept of mobility of elements in

plants – indicator plants – sampling for nutrient analysis. Deficiency of nutrients –

symptom expression – general correction methods. Nutrient deficiency identification

correction in fruits, vegetables, ornamentals. Nutrient deficiency identification correction

in flowers, spices and plantation crops. Nutrient / PGRs formulation – usage and

precautions. Role of PGRs / nutrients for stress tolerance in horticultural crops. Effect of

climate, soil, water and temperature on nutritional and physiological disorders in

horticultural crops.

Practical

Measurement of growth - Estimation of leaf area – leaf area index and – Leaf

Area Duration for different horticultural crops - Growth analysis Net Assimilation Rate –

Relative Growth Rate – Crop Growth Rate - Study of Senescence, Senescence index and

control measures - Seed and bud dormancy. Plant growth regulators – commercial

formulations – role - rooting of cuttings - flowers, fruit set and development - ripening

hormones - inhibitors / retardant / paclobutrazol. Nutrient Deficiency symptoms – basic

principles in identification -Deficiency symptoms in fruit crops, vegetable, flower crops

Spices, plantation crops and correction measures - Rapid tissue test for nutrient

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deficiency identification - Physiological disorders in horticultural crops. Visit to

temperate / Subtropical regions for identification of nutrient deficiency and disorders in

fruits flowers and vegetables.

Lecture Schedule

Theory

1. Growth –differentiation- Development –definitions- types – pattern of growth

– determinate – indeterminate – allometric – growth

2. Growth Parameter – analysis – NAR – RGR – CGR – harvest index –

partitioning efficiency

3. Growth – regulators – classification – role of Plant Growth Regulators in

horticultural crops.

4. PGRs application in fruits and vegetables.

5. PGRs application in Spices and plantation crops and flowers.

6. PGRs for propagation.

7. Senescence – mechanism of senescence – control of senescence by PGRs.

8. Role of PGRs in Post harvest physiology.

9. Mid-Semester Examination

10. Nutrio-Physiology – importance of Macro – Micro elements-essentiality –

mode of translocation

11. Concept of mobility of elements in plants – indicator plants – sampling for

nutrient analysis

12. Deficiency of nutrients – symptom expression – general correction methods

13. Nutrient deficiency identification correction in fruits, vegetables, ornamentals

14. Nutrient deficiency identification correction in flowers, spices and plantation

crops.

15. Nutrient and PGRs formulation – usage and precautions

16. Role of PGRs and nutrients for stress tolerance in horticultural crops

17. Effect of climate, soil, water and temperature on nutritional and physiological

disorders in horticultural crops

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Practical

1. Measurement of growth components, metric analysis

2. Estimation of leaf area – leaf area index and LAD – for different

horticultural crops

3. Growth analytical parameters – measurement of NAR, PGR, CGR and HI

4. Study of Senescence, Senescence index and control measures

5. Preparation of commercial formulations and use of PGRs

6. Role of PGRs’ on of rooting of cuttings

7. Study of inhibitors / retardant / Paclobutrazol on horticultural crops.

8. Study of– PGRs for flowers, fruit set, development and ripening.

9. Nutrient Deficiency symptoms – basic principles in identification

10. Deficiency symptoms in fruit crops and correction measures

11. Deficiency symptoms in vegetable, flower crops and correction measures

12. Deficiency symptoms in Spices, plantation crops and correction measures

13. Visit to temperate / Subtropical regions for identification of nutrient

deficiency and disorders in fruits, flowers and vegetables.

14. Study of seed and bud dormancy

15. Study of physiological disorders in horticultural crops

16. Rapid tissue test for nutrient deficiency identification.17. Practical Examination

References

1. Amar Singh, 1987. Fruit Physiology and Production

2. Bose, T. K., Mitra, S. K. and M. K. Sandhu, Mineral nutrition of fruit crops

3. Frank, B. 1995. Plant Pathology.

4. Kumar. 1995. Introduction to plant physiology.

5. Mallik, C. P. 1990. Textbook of plant physiology.

6. Mitcheli. 1988. Physiology of crop plants. Iowa State University.

7. Noggle and Fritz. 1983. Introductory to plant physiology.

8. Pandey, P. N. and B. K. Sinha. 1989. Plant Physiology.

9. Weston, C.P. 1994. Crop Physiology.

10. Williams P. Jacob. 1979. Plant Hormones and Plant development

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Chapter I Growth and Development

Growth

An irreversible increase in size, changes in form, shape.

• Evaluated by measuring of mass, length, height, area and volume.

• Restricted to living cells accompanied by metabolic process involving

synthesis of macromolecules, DNA, RNA, proteins, lipids, carbohydrates,

secondary metabolites, growth regulators at the expense of metabolic energy.

Differentiation

• Process involved in the establishment of localized differences in

biochemical and metabolic activity (specialized functions) and a structuralorganization that result in new patterns of growth.

Development

• The term is used to encompass the activities resulting from growth and

differentiation.

• During development an orderly progression of transformations resulting in

a characteristic form and chemical composition of plants takes place.

Totipotency

• Isolated plant cells have the inherent capacity to give rise to a whole plant

• The ability of every living plant cell to produce the entire plant is called

totipotency

Morphogenesis

- Development of form or shape of cells and organs

- Direction of cell expansion (decided by orientation of cellulose deposition)

- Control of cell division

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Measurement of Growth

• Plant height, leaf size (length, width, area), fresh weight, dry weight of

different organs (stem, gist, leaves and fruits).

•Cell number in tissues, organs.

• Conc. of chemicals constituent DNA, RNA, soluble protein, CH 2O, lipids

etc.

Vegetative growth

Genetical makeup, Nutrients (16 elements), Environment

Hormonal regulation, Tropic movement, Apical dominance

Reproductive growth

Genetical makeup

Light – Photoperiodism

Temp – Thermoperiodism Vernalization

Moisture

Hormonal regulation - External & Internal

Nutrients - C: N - Ratio

Primary meristem Apical meristem are formed during embryo

development on the seed forms

Secondary meristem - The vascular cambium and meristematic zones

are found near root and shoot tips in the vascular

cambium.

Determinate growth - Germination Leaves flowers fruits

the growth of particular organ is determined.

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Indeterminate growth - Root tips, shoot tips, apical meristem cells have

capacity to regenerate

Determinate plants - Apical bud ends with inflorescence - Monocarpic

senescence

Indeterminate plants- Apical buds always vegetative - Floral buds in axils

Polycarpic senescence

Allometric Growth

Growth of one part of plant may be closely related to growth of another part of thesame plant, even though individual rates are different.

Linear y = ax b log y = log a + b log x

Curvilinear y= ax(b+c log x)

Linear Curvilinear

Log y Log y

Slope b

Log a Log a

0 Log x 0 Log x

Phases of growth - Sigmoid Curve

Y

Steady state

Log Phase (exponential growth)

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Initial lag phase

0 X

S – Shape or Wine cup shape

Growth analysis

LA cm2 plant-1

LAI leaf area of plant / ground area occupied.

LAD L1 + (L1+1) x t2 – t1 L1 – LAI at 1st stage

(in days) 2 L1+1 – LAI at 2nd stage

t1 & t2 – time interval

Leaf area 1SLA = ---------------------------- = -------------cm2 g-1 Leaf dry wt. SLW

Leaf dry wt. 1SLW = ---------------------------- = -------------mg cm-2 Leaf area SLA

Leaf area

LAR = ----------------------------cm2 g-1 Dry weight of the plant (DMA)

W2 - W1 (Log e L2 – Log e L1)ULR or NAR --------------------- x -----------------------mg cm-2 day-1 t2 – t1 (L2 - L1)

(Log e W2 – Log e W1)RGR = ----------------------------

mg g-1

day-1

(t2 - t1)

W2 - W1CGR = -------------------------- W1 & W2 plant dry wt.g m-2 day-1 P (t2 – t1) t1 & t2 - time interval

P = ground area on which W1& W2 has been estimated.

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Vegetative growth

Roots

Food storage roots - carrot, beet, turnip, radish,

Water storage roots - cucurbits

Propagative roots - root suckers cherries, apple, pears

Pneumatopores - Avicenia (mangrove)

Aerial roots - orchids, vanilla, large prop roots of banyan, corn

Contractile roots - pull the plant deeper in to the soil (lily bulbs)

Buttress roots - look like trunk gives stability to tree (fig)

Fungus roots - Mycorrhizae of forest trees

Root nodules - Rhizobium

Stem

Rhizomes - turmeric, zinger

Runner - strawberry

Stolons - tubers at tip of stolons (Irish potato)

Tubers - potato

Bulbs - fleshy leaves with a small stem at the lower end (onion)

Corms - gladiolus, corm, tuber rose

Cladophylls / cladodes / phylloclades - cacti, orchids

Thorns - modified stem (Opuntia)

Tendrils - grapes (modified stem)

- peas & cucumber (modified leaves)

Chapter II Nutrio-Physiology

Arnon & Stout 1939 - Criteria for essentiality of an element

- without which the plant can’t complete its life cycle

- it can’t be substituted by other element

- directly involved in plant metabolism either as a constituent of an essential metabolite

or involved in biochemical reaction

Beneficial elements

C H O Na, Si, Co, V

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Ca Mg S N P K Toxic elements

Al, Cd, Cr, Pb, Se, Ni,

Zn, Fe, Mn Br, I, F,

Cu, Mo, B

Cl

General Role of Mineral Nutrients

Nutritive function: Carbohydrate, Protein & lipids

Structural frame work: By maintaining turgidity

Structural Function: Cellulose, Hemicellulose, Pectin, Structural protein & lipids

Balancing Function: Electrical Neutrality By K + Cl -

Catalytic function: Metal activator / Cofactor in enzymes

Specific Role of Mineral Nutrients

Nitrogen: DNA, RNA, Enzymes, Amino acids, Proteins, Chlorophyll, Alkaloids,

Cyanides

Phosphorus: DNA, RNA, ATP, TPP, NADP, Phospholipids,

Potassium: Stomatal movement, osmo-regulation, Cell turgidity, Structural frame

work, Electrical neutrality, cell wall & membrane permeability, transport

of assimilates

Calcium: Cell wall, spindle formation in cell division, cell wall & membrane

permeability, starch metabolism, calcium binding protein (Calcium

calmodulin)

Magnesium: Chlorophyll, Cofactor in enzymes involving PO4 transfer reactions

(PO4Ase, kinase), cell wall & membrane permeability,

Sulphur: Amino acids (Methionine, cystine, cysteine), Ferredoxin (non heam Fe-S

compound) Enzymes tertiary structure,

~CoA, thiamine, diallyl disulpide. Mustard oil (glycosides, glucosinolates)

Iron: Redox potential of the cell, Cytochrome. Plastoquinone, Ferredoxin, Enzymes

(Dehydrogenase, catalase, peroxidase, oxidases)

Zinc: Auxin metabolism, Tryptophan amino acid synthesis, Cofactor in enzymes

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(alcoholic dehydrogenase, carbonic unhydrase)

Manganese: Photolysis of water, Cofactor in enzymes (carboxylase &

Decarboxylase), respiratory enzymes

Copper: Plastocyanin, plant defense phenolic compounds, Cofactor in enzymes

(Polyphenol oxidase, Laccase)

Boron: Sugar transport, pollen viability

Molybdenum: Cofactor in enzymes (NRAse), nitrogen metabolism

Nitrogenase (Fe & Mo bearing N2 fixing microbes)

Chlorine: Stomatal movement, Osmo-regulation, Cell turgidity, Electrical neutrality

Beneficial elements

Na – Atriplex, halogeton, sugar beet, celery, spinach, turnip, coconut, cabbage,

radish, rape, chenopodiaceae

Si – Rice

Co – Legumes

Deficiency Symptoms:

Nitrogen: Deficiency - starts from older leaves, whole plant affected

Leaves – small, dark green – light green – yellow – brown – die

Plants - weak, small, few branches/tillers with anthocyanin

Pigments purple colouration in leaves, petiole & stem, low

soluble protein early maturity, short

vegetative growth,

Stem - weak, slender, spindly,

Roots – less branching

Flowers – few, poor fruit setting, small fruits, poor quality

Phosphorus: Deficiency - starts from older leaves, whole plant affected

Leaves – small, thick, dark green with purple colouration

Grey - brown – die

Plants – Short, small, with pigmentation

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Flowers – delayed flowering - poor fruit setting, small fruits,

poor quality, slow maturity

Root – Poor root formation

Potassium: Deficiency - starts from margin/ tip of older leaves

Leaves – Yellowing starts from tip/leaf margin, bluish green

leaves marginal, Scorching- tip burning, necrotic leaves die

scorched to necrotic, leaf lets curl downward(curl towards

under surface/ backward)

Stem - weak

Flowers – few, poor fruit setting, small fruits with sour taste

Magnesium: Deficiency - starts from older leaves, interveinal chlorosis

Reddening of leaves, mottling, reddish brown necrotic spots

Leaves with marbling with tints of orange & purple colours.

Interveinal chlorosis

Zinc: Deficiency – Rosettes terminal, starts from older leaves,

interveinal chlorosis

Leaves – small, internodes constricted, mottle leaf

Plants – dwarf, rosette, malformed

Flower – flower shedding, poor fruit set,

Fruits – small, poor quality

Calcium: Deficiency - starts from younger leaves, distorted, margin

Irregular, Yellowing starts from tip of young leaves, leaves

spotted & necrotic

Terminal buds- twisted, hooked, die-back of young buds

Root – rotting

Affect growing meristems

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plants highly branched

Boron: Deficiency - starts from younger leaves, chlorotic spots

Yellowing starts from base of young leaves Leaves

thickening, brittleness(transpiration affected), curling,

wrinkling, wilting, root tips necrotic,

Terminal buds- abnormal, twisted, hooked, die-back of young

Buds stimulate lateral growth

Young shoots – discoloration, darkish blue colour, corky,

cracked water soaked, blackening of vascular bundles in

meristems plants highly branched

pollen growth affected, (parthenocarpic fruit set)

reduced flower & fruit formation

Sulphur: General yellowing, similar to nitrogen deficiency

Yellowing starts from younger leaves,

Plants rigid, brittle, thin stem, shoot more affected than root

Iron: Deficiency - starts from younger leaves

Young leaves – bleaching of Chlorophyll

Green – yellow – white – die

Manganese: Deficiency - starts from younger leaves, interveinal chlorosis

Leaves- chlorotic, mottling, dark and light green bands

Necrotic spots, streaks.

Copper: Deficiency - starts from younger leaves, interveinal chlorosis

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Leaves- chlorotic, withering of young shoots (lack of turgor), die

back Gummosis (gum pockets surround the central pith), leaf curl

upwards, poor quality of fruits

Molybdenum: causes deficiency of nitrogen, interveinal chlorosis, whole

plant affected, necrotic leaf margins due to NO3-

accumulation, leaf lamina not formed, mid rib is present

Indicator Plants

N – Maize and non legume cover crop in orchards

P – Tomato, maize

K – Potato, tomato, cucurbits, bean. alfalfa, clover, tobacco, corn and cotton

Ca - Alfalfa

Mg – Portulaca, oxalis, apple, potato and cotton

S – Tea

Fe – Eucalyptus, acacia and morning glory

Zn – Citrus, peaches, field bean, onion, tomato, cotton and sorghum

Mn – Apple, cherry, citrus, sugar beet, raspberry and oats

Cu – Labiatae (Mint family-basil) and Caryophyllaceae (Pink family)

Mo – Brassica, beetroot, tomato, spinach, lettuce

B – Alfalfa, Apple, Pear, Cabbage, Brussels sprouts, & cauliflower

General Deficiency Diseases

N – Firing old leaves

Cucumber fruits pointed at blossom end,

Onion small bulbs, early maturity

P – Delayed maturity, Dark green leaves

K – Tip burning, Marginal scorching, Firing of leaf tips and margins,

apple – marginal scorching, fruits small & poorly coloured

tomato & grapes – uneven ripening

Potato – tuber flesh is bluish

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Mg – Reddening, marbling in many crops

S – Tea – Tea yellow

Cruciferae – narrow leaves

Onion – low pungency & more palatable

Fe – Bleaching of chlorophyll (devoid of chlorophyll)

Ca – Root rotting, Die back, Distorted, twisted and coiled

Tomato & pepper – Blossom-end rot

Grapes – Blossom-end rot & Stalk necrosis

Pomegranate – Fruit cracking splitting

Apple – Bitter pit, water core, Pear – Cork spot

Celery – Black heart

Brussels sprout – Internal browning

Carrot – Cavity spot

Chinese cabbage – Tip burn

Zn – Interveinal chlorosis, Rosette, little leaf, dwarfening

Apple – small fruits

Mn – Dark and light green band of chlorosis, Grey speck

Peas – March spot/ Marshy spot

Sugar beet- Speckled yellow

Sugar cane – Pahala blight

Cu –Gummosis, Withering (lack of normal turgor), Die back, Cupping or

bowing up of leaves (pendula), splitting of young fruits

Avocado – S shaped shoots

Citrus – Gummosis or Exanthema (gummy excrescence in fruit rind &

young stem)

Onion – Scales pale yellow

Pear – Witches broom

Mo – Citrus – Yellow spot

Cauliflower and Broccoli – Whip tail

Oats – Blue chaff

B – Grapes – Hen & Chicken

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Apple – Cork disease, Witches broom

Cabbage & Brussels sprouts – Hollow stem

Turnip & Celery - Cracked stem, hollow & cracked root

Cauliflower – Brown or red rot

Tobacco – Top sickness

Beet root – Crown & Heart rot

Pomegranate – Fruit cracking splitting

Amla – Fruit necrosis

Beans – witches broom

Physiological Disorders:

Mango

Black tip – fumes of brick kiln

Leaf scorch- Chlorine toxicity

Spongy tissue – Ca involved

Soft nose or Tip pulp – Ca involved

Malformation – nutrients? Mites? Viruses? Fungi?

Citrus

Granulation – juice sacs hard (High temp., RH nutrients Zn Cu K involved)Rind pitting – K reduced pitting

Sapota

Malformation of terminal shoot – Fungi?

Pomegranate

Sudden decline – Sudden drop in temp. late autumn and early winter

Fruit cracking - Boron

Annonas

Stone fruit – Competition among the developing fruits

Fruit cracking – Sudden high fluctuation in water supply

Leaf scorching – Chlorine toxicity

Tomato

Fruit cracking – Sudden high fluctuation in water supply

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Vegetable & Fruit crops

Flower shedding – biotic & abiotic stresses,

Fruit drop - biotic & abiotic stresses

Poor fruit quality – Extreme temp.

Poor flower colour – High temp.

Chapter II Plant Growth Regulators

Hormone

An endogenous compound, which is synthesized at one site and transported to

another site where it exerts a physiological effect in very low concentration. But ethylene

(gaseous nature), exert a physiological effect only at a near a site where it is synthesized.

Classified definition of a hormone does not apply to ethylene.

Plant growth regulators

• Defined as organic compounds other than nutrients, that affects the

physiological processes of growth and development in plants when applied in

low concentrations.• Defined as either natural or synthetic compounds that are applied directly

to a target plant to alter its life processes or its structure to improve quality,

increase yields, or facilitate harvesting.

Plant Hormone

When correctly used, is restricted to naturally occurring plant substances, there

fall into five classes. Auxin, Gibberellins, Cytokinin, inhibitors and gas ethylene. Plant

growth regulator includes synthetic compounds as well as naturally occurring hormones.

Plant Growth Hormone

The primary site of action of plant growth hormones at the molecular level

remains unresolved.

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Reasons

• Each hormone produces a great variety of physiological responses.

• Several of these responses to different hormones frequently are similar.

• The response of a plant or a plant part to plant growth regulators may vary with thevariety of the plant.

• Even a single variety may respond differently depending on its age, environmental

conditions and physiological state of development (especially its natural hormone

content) and state of nutrition. There are always exceptions for a general rule

suggesting the action of a specific growth regulator on plants.

• There are several proposed modes of action in each class of plant hormone, with

substantial arguments for and against each mode.

Hormone groups

Auxins - Substances generally resembles IAA and have the ability

to stimulate the elongation of coleoptiles.

Gibberellins - are diterpenoids, which have the ability to elongate the

stem of green seedlings especially certain dwarf and rosette

types.

Cytokinin - Usually substituted Adenines, which resembles zeatin

(Naturally occurring cytokinin in Zea mays) and have the

ability to stimulate cytokinesis in cultures of tobacco cells.

Ethylene - Gaseous regulator that stimulate isodiametric growth

in the apices of dicot seedlings.

Inhibitors - are regulators of growth, which originally depress the

cell enlargement activity.

Biosynthetic Precursor

1. IAA (Weak acid) - Tryptophan

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2. GA3 (Weak acid) - Mevalonate

3. Ethylene - Methionine

4. Cytokinin (Zeatin) - Adenine Mevalonate

5. ABA (weak acid) - Mevalonate

Auxin

Indole group – IAA, IBA, IPA

Naphthalene group - NAA

Phenoxy group – 2,4-D, 2,3,5 - T

Dichlorophenoxy acetic acid (2,4-D)

2,4,5 – Tricholorophenoxy acetic acid (2,4,5-T)

IAA functions

• Promote the accumulation at K + and Cl-

• Increases the osmotic pressure

• Antioxidant

• Increase the elasticity of the cell wall and plasticity

• Reverses red light inhibition of mesocotyl elongation

• Geotropism – IAA is transported to darker side of shoot• Phototropism – IAA is transported to dark side of shoot

• Leaf senescence – delays

• Leaf abscission – leaf application inhibit. Proximal application promotes

• Flowering may promote

• Fruit setting – parthenocarpic fruit setting.

GA – Gibberella fujikuroi (Fusarium moniliforma)

Short tip, bud primordia, developing seeds

GA antagonistic to ABA – 55 Gas

GA increases maleness, breaks dormancy, stem elongation, cell elongation in

apical meristem.

GAs increase the hydrolytic enzymes

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Reduces the Juvenile period

Cause flowering in plants belonging to diverse response types

Delays senescence (retains chlorophyll)

GA induces – ∝ amylase protease, RNAse, Esterase, Acid PO4 ase

Induce flowering and fruit set

Parthenocarpic fruit set

GA is a substitute for light and low temperature (cold)

Cytokinins

Substituted pureness

Induces cell division

Biosynthesis via RNA and biosynthesis of free cytokininsBreaks dormancy, causes femaleness

Auxin and Kinetin ratio decides the root, short formation

Root tip in the sit of cytokinin synthesis

Structural component of RNA molecules

Helps in protein synthesis.

Delays senescence & protein degradation

Counteract apical dominance

Interact with light in seed germination, pigment formation and cell development

Richmond – Lang effect – delay of senescence (1957)

ABA

Chloroplast could be the site of ABA synthesis

Fruits constitute the riches source of ABA

2-trans ABA – biologically active

2 cis ABA – active1. Synthesis by isoprenoid pathway from mevalonic acid

2. oxidation of xanthophylls.

Mevalonic acid is also precursor of GA

GA – diterpene

ABA – sesquiterpene

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ABA is antagonistic to GA

Causes bud dormancy – inhibition of germination

Accelerate senescence – stimulate abscission

Causes closer of stomata

Production of protein in mediated through ABA

ABA is an inhibitor inhibits cell division and elongation

ABA inhibits the synthesis of DNA and RNA

Inhibit flowering in long day plants in SD condition

Ethylene - antagonist CO2

All the plant part will produce ethylene

It is regularly flushed out the plantInhibition growth Reversed by CO2

Leaf epinasty Chlorophyll degradation

Abscission induction causes femaleness

Fruit ripening promotes abscission and

Seed germination senescence of flowers.

Bud sprouting

CO2 fruit remain fresh

Removal of CO2 by KOH enhances ethylene activity

Increase later flow, Accelerate senescence

Ethylene promote leaf abscission

Increases the activity of IAA oxidase

Increases the activity of chlorophyllase and causes breakdown of chlorophyll

Waxing fruits results in low oxygen availability for ethylene production.

Ethylene – Auto catalytic (or) ethylene production is common and ripening fruits and

senescing tissues.

• Breaking of seed and bud dormancy

• Root initiation

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• Stem strengthening

• Lateral branching

• Leaf epinasty

•Flower initiation

• Flower and fruit thinning

• Fruit growth stimulation

• Initiation of fruit ripening

• Flower senescence

• Fruit and leaf degreening

• Leaf abscission and senescence

Phenols

Monophenols - Salicylic acid, ferulic acid, P-coumaric acid

Dipenols - Caffeic acid, catechol, , hydroquinone,

Polyphenols - colour of petals occur as glycosides anthocyanidin –

Anthocyanin

Tannins – gallic acid

Lignin – polymerised poly propane units

Triacontanol - long chained alcohol from alfalfa

Increase dry weight, effect on photosynthesis

Might increase uptake of nutrients

Brassinolide - steroid from pollen of the rape plant accelerate plant growth.

Chloromequat (CCC) - reduce the size of the overall plant.

Mepiquat chloride improves the standing power of crops.

Salicylic acid –Improves vascularisation

Paclobutrazol – Induces flowering

CCC, Paclobutrazol – Anti Gibberellins

MH – Anti auxin

Alar B-Nine, Daminozide – Dwarfening plant size

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Uses of Plant growth regulators in Horticultural crops

Germination and dormancy

GA is the most potent germination promoter breaking seed dormancy

Peach, sour orange, rough lemon, sweet orange, beans, peas, cabbage, cucumber,

cucurbits, GA treated lettuce seed germinate in darkness.

GA replaces cold requirements

MH – suppress sprouting in potatoes and onions

GA – breaks dormancy of potato tubers.

Rooting and Plant Propagation

IBA -the best and most commonly used chemical IBA decomposed relatively slowly by the auxin –destroying enzyme systems. IBA moves very slowly in the

plant, much of it is retained near the site of application.

produce –strong fibrous root system

NAA in more toxic than IBA.

Amides of both compounds are also effective amide of NAA in less toxic than the

acid itself

2,4-D and 2,4,5-T Promote root wig at low concentration but their toxic

limit in near the opt. Concentration.

Phenoxy acids produce – bushy, stunted and thickened root system

IBA- practical uses

Rose , tea, winged bean, grapes, ficus, ixora, bougainvillea, jasmine, eggplant ,

hibiscus, apples, peach, plum, rubber

Quick dip method:

Basal end of cuttings dipped for a few second in a cove solution (upto 10,000 ppm

in alcohol)

Prolonged soaking method:

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Basal end of cuttings are soaked in dilute solution (10-500 ppm) upto 24 hours.

Powder method:

Basal end of cuttings are treated with growth regulator in an earlier (clay or talc)

conc. 500 to 1000ppm.

Fruit set and Development

-Auxin type compound most frequently used (NAA)

GA – set fruit in some sp that does not respond to others.

Ethephon - female flowers in cucumber

2,4-D, NAA and IBA - cashew

GA4 + GA7 and b- benzyl adenine- apple fruit quality

Gametocides

♂ sterility Ethrel - Cucurbits, Sugar beet

MH - grape, pepper, tomato

GA3 - cabbage, cauliflower, kale, lettuce

TIBA - grape, tomato,

Plant and Organ size

GA – breaks dwarfness

Increase size of grapes

Triacontanol - Increase dry weight, effect on photosynthesis

Might increase uptake of nutrients

Brassinolide - steroid from pollen of the rape plant accelerate plant growth.

Chloromequat - reduce the size of the overall plant.

Mepiquat and ethephon improves the standing crop.

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Abscission

The control of abscission does not reside in any one hormone or environmental

factor but is regulated by a complex interaction of environment, hormones, and

physiological status of plant

- Auxin, ethylene and ABA are most directly involved, others have indirect

effect

Citrus Thinning

Cycloheximides – antifungal, antibiotic, - loosen citrus fruits (0.1/b per acre) it

damages the flower and immature fruits.

Release - effective abscission inducer.

Apple thinning

Ethrel - plant growth regulation (PGA)

Antitranspirant

should be long lasting, cheap and Non toxic

(PMA) Phenylmercuric acetate – have toxic effects on the mesophyll and

photosynthesis in addition to the influence on guard cells.

Chemicals as metabolic antitranspirants

ABA - bean, citrus, cucumber, pepper, tomato

Chlormequot - tomato

Daminozide - tomato

8 – hydroxyquinoline – tomato, strawberry

IAA – Tomato

Phenyl mercuric acetate - tomato,

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Chapter III Senescence

Assimilate Partitioning in Horticultural crops

Transport system:

Soil to root → absorption

Root to leaves → Ascent of sap

Leaves to atmosphere → Transpiration

Xylem transport – Passive (water, minerals & cytokinin)

Xylem = parenchyma + fibres + vessels + trachieds + ray cells

Non living but functional (mainly dead cells)

Unidirectional movement

Phloem transport – Active (photo assimilates- sugars, amino acids, organic acids,

hormones & other biomolecules) Living functional – Bi-directional movement

Phloem transport - symplast – via plasmodesmata depends on the rate of

cyclosis within the cell.

Provide a route for the movement of molecules from cell to cell without

crossing the plasma membrane.

Movement between cells in phloem sieve tubes occurs through sieve

plates.

Apoplast: movement of molecules through the (aqueous part of the cell wall

matrix) apparent free space present in cell wall & intercellular

airspace

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cuticles, casparian strip and lignified walls are resistant to apoplastic

transport.

Phloem loading-Assimilate moves from mesophyll to sieve tube (Apoplast)

Phloem unloading- Assimilate moves from sieve tube to sink cell (Apoplast)

Apoplast pathway – through cell wall & intercellular airspace

Source – regions of photo-assimilate production, export photo-assimilates

- chlorophyllous tissues (leaves, stipules, fruit wall, young stem, pedicel, awns,

peduncle, calyx, bract etc)

Sink - regions of photo-assimilate consumption, import photo-assimilates

Growing regions, storage organs (respiration, growth and storage)

Source strength: size x activity

Differences in CO2 fixation (Rubisco & PEPCase)

Leaf characters – size, thickness, mesophyll size, compaction, vascular bundle

Carrying capacity of sieve element (temp., H2O, nutrients, hormone)

Sink strength - Potential capacity of the sink to accumulate assimilates

Competition among different sink

Harvest Index:

HI = {Yield (Eco)/ Yield (Biol)} x 100

Harvest Increment: Photo-assimilates partitioned to harvestable organ - It is very

difficult to estimate

Improve HI in Annual horticultural crops

Increase biomass production (DMA) & High photosynthetic rate

Synchronized development of reproductive organ - Reproductively determinate

High source strength at the time of sink differentiation

Reduced growth of non harvestable organ

Reduced leaf growth at reproductive stage with high LAD

Optimum LAI and early peak LAI

Prolonged and faster storage, enhanced competitiveness among of the storage

organ

Improved HI by increased size and number of sink organ

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Decline in duration of Veg. growth and increased duration of Rep. growth.

Reduced root weight with adequate nutrient and H2O

Developmental plasticity (small surplus source for stress)

Quick export of photoassimilates to avoid end product inhibition

Efficient root system

Limitations

Source: leguminous vegetables

Sink: Grain amaranthus

Sink limitation:

Late anthesis (Long Veg. phase)

Indeterminate (Veg. & Rep. growth)

Veg. growth at Rep. phase

Less sink number and size

Hormonal imbalance

Stress

Source limitation:

Low canopy photosynthesis

Low optimum LAI

Slow peak LAI (lag vegetative growth)

Low LAD at filling

Early leaf senescence

Stress – nutrients, water

PGRs:

Auxin promotes source uptake

ABA in leaves causes closer of stomata (Inhibit CO2 fixation)

Cytokinin delays senescence of source and sink

Cytokinin in sink increases photo assimilates import

Ethylene induces senescence process.

Assimilate Partitioning:

• Leaf subtending the inflorescence supply major portion of photo-assimilates for

fruits development

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• In case of damage to the leaf subtending the inflorescence, the developing fruits

mobilize assimilates from near by leaves

• Distance between the source and sink decides the rate of fruit development

• Current photosynthesis is important for fruit development in annual horticultural

crops

• Different kinds of biotic and abiotic stresses adversely affect assimilate

partitioning

• In perennials, stem always act as a strong storage pool for assimilates and

nutrients. Previous season growth is important for higher productivity (In mango,

SW monsoon rainfall is important for higher productivity)

• Remobilizations occurs from stem to developing fruits

Fruit set, development & ripening

Flowering

GA - Maleness

ABA inhibit flowering in LDP and induce flowering in SD Plants

CCC inhibit flowering in SD plants act as antigibberllins

C2H4 induces femaleness in cucurbits at 3 leaf stage.

C2H2, C2H4 and NAA induces flowering in pineapple

Stress - Moderate stress early flowering

Severe stress - delayed flowering - flower and pod shedding

Parthenocarpy – formation of fruit without seed

i. Fruit development without pollination (Tomatoes, pumpkins, cucumber,

bananas, pineapple)

ii. Fruit development due to stimulus received by pollination followed by

unsuccessful fertilization (Poa)

iii. Abortion of embryos before attaining maturity of fruits (Cherries, peaches& grapes)

Limitations of fruit set:

- Due to limited pollination

- Due to limited nutrients

- Due to abscission of flowers and young fruits

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- Pollenizer for cross fertilization for self barren trees

- honey bee for pollination

- parthenocarpic fruit set

- defective flowers (due to fundamental constituent of protoplasm) - imperfect flowers,

heterostyly, dichogamy, due to fundamental constituent of protoplasm

Unfruitfulness

Nutritive condition, soil type, water supply, cultural practice, wind low temp

Pistillate flowers produce – fruits parthenocarpically

- Abortion of flower and flower buds before blossoming

- Nonviable pollen & self sterility

Self-sterility – poor pollen tube growth in the style – hormones, low temp

- Difference in maturity of pollen grain & pistil (or) ovule

- Delayed pollen germination

Detective pistils in exhausted (or) weakened plants, overbearing, poor nutrition,

drought

Environment – condition at the onset and during flowering affect fruit setting

Nutrient supply – hen & children disease in grapes

Pruning and grafting – alter apical dominance, control reproductive phase

- C/N ratio, normal bisexual flowers

- Locality – soil, temp, humidity & light influence

Season – Age & vigour of plant, temp, light, H2O relations, rain wind

proper stage of maturity at picking ensures better quality of fruits

Fruit development:

Fruit development – depends on events taking place in ovule

Fruits – ripened ovary with attached parts

1. Well developed carpel – Orange, grape

2. Epigynous flower – receptacle in a part of the fruit (eg.) apple, banana, cucumber

3. Ripened ovary – tomato

Berry – Entire ovary wall develops into a fresh – tomato, brinjal, guava, grapes, avocado

Hesperidium – Citrus multicellular enlarged, juicy, saclike out growth from the surface of

the carpal walls are edible

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Pepo – One or three celled syncarpous pistil with parietal placentation

Drupe – Exocarp thin, mesocarp fleshly, endocarp stone – almond, mango, peach,

apricot, plum, coconut, cherry

Pome – Fleshy edible part is thalamus

Aggregate – Collection of simple fruits or fruit lets

Strawberry – edible fleshy and much elongated receptacle rasp berry.

Multiple fruit – inflorescence takes point in the formation of fruit - pineapple, mulberry,

fig, jack fruit

Pericarp – Date, custard apple

Pericarp & placenta – tomato, brinjal

Mesocarp – papaya, mango, melon

Mesocarp & endocarp – banana

Mesocarp, endocarp & placenta – cucumber

Thalamus – strawberry, pineapple, apple

Thalamus & pericarp – guava

Peduncle & cotyledon – cashew

Endosperm – coconut

Receptacle – fig, pear

Bract, perianth & seed – jack

Juicy placental hair – citrus

Juicy outer coat of seed – pomegranate

Phases of fruit growth

I Fruit growth rates – two important stages

- Growth of pericarp – Epicarp, mesocarp & endocarp (Rapid and slow growth)

- Growth of embryo & endosperm

- Simple sigmoid- apple, pineapple, strawberry, pea tomato

- Double sigmoid – peach, apricot, plum & cherry (stone fruits); fig & grapes

(Nonstone fruits)

II Mobilization:

- Large size fruits import food from other parts of the plant

III Fruit size:

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- Fruit size correlated with cell size (cherries)

- Large fruit size through inter cellular spaces development in the second half of fruit

enlargement (apple)

- Loading of sugars into the fruit

IV Role of seed:

- seed regulate fruit growth

- Removal of fertilized ovule terminates fruit growth

- Geometry of fruits reflects seeds distribution

- Seeded regions of fruits distinct from parts of unseeded region

- Fruit size is + vely to seed number (strawberry)

Parthenocarpic fruits differ in shape from seeded fruits of same variety

Seedless pear oval; seeded pear pear shaped

Seed influence strong on the growth of fleshy fruits

Growth substances – Endogenous Auxin play important role

Single sigmoid – Auxin controlled

Double sigmoid – I phase Auxin and GA controlled

II phase osmotic accumulation of carbohydrates

ABA and C2H4 involved in fruit drop

Tomato seeds contain ferulic acid which causes dormancy

Fruit drop:

- Fruit resulting from self pollination are more susceptible to fruit drops

- Auxin content is low - fruit drop is common

- ABA and Ethylene involved in fruit drop

- C2H4 inducing compounds are successfully used in mechanical harvesting

Maturity – age, shape, angularity, size, appearance, texture, sp. gr

Pectin, starch, sugars, sugar-acid ratio

Maturity attainment of full size

Matured fruits maximum starch and sp. gr

Late harvest – Lowers shelf life

Fruit Ripening:

Ripening – Loss of chlorophyll

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Increase in ° brix

Increase in titrable acidity

Decline in pectin and water soluble pectin

Lowering respiration increase shelf life

Ripening: Fruit ageing - Softening of the flesh

- Changes in pigmentation and flavour

- Loss of chlorophyll

- Appearance of carotenoids

- Increase in sugars & volatile compounds adds flavour

Polysaccharides sugars, ↓in acids

CO2 & C2H4 production increase

Increase in activity of malic enzyme and pyruvic carboxylase leading

to climacteric rise in CO2 production – climacteric fruits

hydrolytic enzymes

During ripening – sudden upsurge in respiration followed by deterioration – banana,

guava, mango, fig, jack, papaya – rich in carotenoids fructose disappears –

require high energy for fruit ripening increase in RNA & mRNA

Increase in chlorophyllase, hydrolase, lipase, lipoxidase, peroxidase

C2H4 bring about climacteric in non-climacteric fruitsUnsaturated hydrocarbon promote ripening

Single gradual decline in respiration – citrus (lemon, lime, oranges, grapes,

pomegranate, pineapple – rich in anthocyanins

N2 & CO2 & ↓O2 prevent the climacteric rise.

Softening – cell wall-degrading enzymes

Hydrolysing of cell content (pectic enzymes) middle lamellae

Increase in methylation of galacturonic acid

Hydrolytic changes – sugar formation

Changes in pigments Decrease in chlorophyll (chlorophyllase) increase in carotenoids

& anthocyanins (phytochrome involved)

Low temperature – Increase in colour & High temperature – Poor colour development

Flavour substances – Esters, aldehydes, ketones, loss of astringent materials, decrease in

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phenolics

Climacteric fruits- banana, mango, apple, pear, tomato

Increase in respiration during ripening-after reaching a peak the rate of

respiration falls

Low O2 and high CO2 affect climacteric rise

Polythene storage lowers O2 and increase in CO2 extends shelf life

C2H4 stimulates climacteric rise

Non-climacteric fruits – citrus, pepper, peanuts (Steady respiration)

Ripening – Respiration is a source of energy for synthesis of new enzymes

required for ripening C2H4 ripening hormone, but it has no effect on

ripening but de-greening occur

Photoperiodism (Vince-Prue, 1975)

• Day length controls initiation and development of flowers

• Asexual reproduction

• Formation of storage organs

• Onset of dormancy

• Specific biochemical pathways regulate different responses

Garner & Allard – Maryland Mammoth tobacco

Borthwick & Parter – Soybean

Hamner & Bonner – Xanthium strumarium

Chailakhjan – Chrysanthemum & Perilla

Melcher’s & Lang Hyocyamus niger (henbane)

Vince Prue – specific biochemical pathways regulate different responses

Night length is more important than day length

SDP – (< 12 hrs) Dahlias, Asters, Chrysanthemum, Goldenrod, poinsettias, Salvias,

Straw berries, maize femaleness, sweet potato, Soybean var. BiloxiChenopodium, coffea arabica

SDP- I Qualitative (or) absolute

Chrysanthemum, Soybean Cv. Biloxi

Chenopodium, Ipomea batatas

Coffee arabica, Xanthium strumarium (cocklebur)

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Tobacco Cv Maryland mammoth

II Quantitative cosmos, amaranthus, zinnia, sunflower, rice, potato,

strawberry (runner –LD), onion (bulb-LD), datura, dahlia, aster, poinsettia,

LDP - (> 14 hrs) Beets, lettuce, spinach,

Spinacea oleracea – Spinach, Oats, barley, Opium poppy,

Radish - Raphanus sativus, alfalfa, sugarcane, Lettuce

LDP - I Absolute (or) Qualitative: Beta vulgaris, Avena sativa, Raphanus sativus,

Spinacea oleraceae, Hordeum vulgure

II Quantitative: Lettuce, alfalfa, opium (poppy), wheat, barley, oats, Brassica

rapa, Pisum sativus, Secale cereale

IDP - (12 – 14 hrs) Indian grass & other grasses, Ocimum basilicum

DNP - (not regulated by day length) roses, sunflower, tomatoes, beans, carnations,

nasturtium, snapdragon, Dandelions, calendulas, paddy, cucumber, maize

Critical day length - expression of photoperiodic response

SDP do not flower if the day length is longer than their critical day length.

LDP do not flower in light periods shorter than their critical period.

Hypothetical Plant hormone – Florigen Floral stimuli is transmittable

Photoperiod (hours) SDP LDP

LLLLLL 8 h DDDDDDDDDDDD 16 h F VLLLLLLLLLLLLLLL 16 h DDDD 8 h V F

LLLLLL 8 h DDDDD L DDDD 16 h V F

LLLLLL D LLLLLL 16 h DDDD 8 h V F

LLLLLLL 8 h DDDDD 8 h xxxxxxxxx V F

LLLLLLLLLLLL 16 h DDDDDDDDDDDD 16 h F V

DDDDDD LL DDDDDD LL DD LLLLLL DD LLLLLL

X

SDP LDP SDP LDP SDP LDP

F V F F V F

Duration of dark without any break is more important for perceiving photo stimuli.

Thermoperiodism - The beneficial effects on plant growth of alternating either day-time

and lower night time temperature.

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Vernalisation - The enhancement of subsequent flowering response by low temp (0-

100C) treatment of inhibited (or) young seedlings

Gassner, Munreek and Whyte, Lysenko, Gregory and Purvis, Lang and Melcher,

Requirements: water, oxygen and low temp. 0-10 ºC (opt. 3 - 7 ºC)

Seed Vernalisation

– Chicory - Cichorium intybus

– Carrot – Daucus carota

– Sugar beet – Beta vulgaris

– Winter cereals – Oats, Barley, Rye, Wheat,

– Indian Mustard, Turnip, Lettuce

Plant Vernalisation - Rape, Celery, Digitalis, Oenothera

Hypothetical plant hormone - Vernalin

Crp.211 Theory

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