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Transcript of 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