Botany BasicsBotany Basics

Crop Science 1Crop Science 1

Fall 2004Fall 2004

September 14, 2004September 14, 2004

IntroductionIntroduction

Plants are essential to life on earthPlants are essential to life on earth Primary food source for humans and other Primary food source for humans and other

animalsanimals Provide fuel, replenish the earth's oxygen Provide fuel, replenish the earth's oxygen

supply, prevent soil erosion, slow down wind supply, prevent soil erosion, slow down wind movement, cool the atmosphere, provide movement, cool the atmosphere, provide wildlife habitat, supply medicinal compounds, wildlife habitat, supply medicinal compounds, and beautify our surroundings and beautify our surroundings

IntroductionIntroduction

Many plants are familiar to us based on Many plants are familiar to us based on their external structurestheir external structures

Internal structures and functions often Internal structures and functions often are overlooked. are overlooked.

Understanding how plants grow and Understanding how plants grow and develop helps us capitalize on their develop helps us capitalize on their usefulnessusefulness

IntroductionIntroduction

This course focuses on This course focuses on vascularvascular plants plants Contain water- and nutrient-conducting Contain water- and nutrient-conducting

tissues called xylem and phloemtissues called xylem and phloem Ferns and seed-producing plants fall into Ferns and seed-producing plants fall into

this categorythis category

IntroductionIntroduction

MonocotsMonocots MonocotyledonousMonocotyledonous Grasses and cereal Grasses and cereal

grains grains Produce only one Produce only one

seed leafseed leaf

DicotsDicots DicotyledonousDicotyledonous Two seed leavesTwo seed leaves

Monocots vs DicotsMonocots vs Dicots

Plant Life CyclesPlant Life Cycles

Based on its life cycle, a plant is Based on its life cycle, a plant is classified as an classified as an AnnualAnnual BiennialBiennial Perennial Perennial

AnnualAnnual

Most common are weedsMost common are weeds Completes its life cycle in 1 Completes its life cycle in 1

year. year. Go from seed to seed in 1 Go from seed to seed in 1

year or growing season. year or growing season. During this period, they During this period, they

grow, mature, bloom, grow, mature, bloom, produce seeds, and die. produce seeds, and die.

Summer annuals - spring and Summer annuals - spring and summersummer

Winter annuals - fall and Winter annuals - fall and winter. winter.

BiennialBiennial

2 years to complete its 2 years to complete its life cyclelife cycle

First season, it produces First season, it produces vegetative structures vegetative structures (leaves) and food (leaves) and food storage organsstorage organs

The plant overwinters The plant overwinters and then produces and then produces flowers, fruit, and seeds flowers, fruit, and seeds during its second season during its second season

Swiss chard, carrots, Swiss chard, carrots, beets, and parsleybeets, and parsley

PerennialPerennial

Live more than 2 years Live more than 2 years Grouped into two categories: Grouped into two categories:

Herbaceous Herbaceous Have soft, nonwoody stems that Have soft, nonwoody stems that

generally die back to the ground generally die back to the ground each wintereach winter

New stems grow from the New stems grow from the plant's crown each springplant's crown each spring

Woody Woody Trees and shrubsTrees and shrubs Have woody stems that Have woody stems that

withstand cold winter withstand cold winter temperaturestemperatures

Internal Plant PartsInternal Plant Parts

Cells Cells The basic structural and physiological units of plantsThe basic structural and physiological units of plants Most plant reactions occur at the cellular levelMost plant reactions occur at the cellular level

TissuesTissues Large, organized groups of similar cells that work Large, organized groups of similar cells that work

together to perform a specific functiontogether to perform a specific function A unique feature of plant cells is that they are A unique feature of plant cells is that they are

readily readily totipotenttotipotent Almost all plant cells retain all of the genetic Almost all plant cells retain all of the genetic

information necessary to develop into a complete information necessary to develop into a complete plantplant

MeristemsMeristems

Meristems are a plant's growing pointsMeristems are a plant's growing points The site of rapid, almost continuous cell division The site of rapid, almost continuous cell division These cells either continue to divide or begin to These cells either continue to divide or begin to

differentiate into other tissues and organsdifferentiate into other tissues and organs You can manipulate meristems to make a plant do You can manipulate meristems to make a plant do

something you want, such as change its growth something you want, such as change its growth pattern, flower, alter its branching habit, or produce pattern, flower, alter its branching habit, or produce vegetative growthvegetative growth

Plant OrgansPlant Organs

Plant Organs include external plant structures Plant Organs include external plant structures such as:such as: LeavesLeaves StemsStems RootsRoots FlowersFlowers Fruits and seeds Fruits and seeds

Each organ is an organized group of tissues Each organ is an organized group of tissues that works together to perform a specific that works together to perform a specific functionfunction

External Plant PartsExternal Plant Parts

Plant Organs can be divided into two groups: Plant Organs can be divided into two groups: Sexual reproductiveSexual reproductive parts parts

Produce seedProduce seed Include flower buds, flowers, fruit, and seedsInclude flower buds, flowers, fruit, and seeds

VegetativeVegetative parts parts Include root, stems, shoot buds, and leavesInclude root, stems, shoot buds, and leaves Are not directly involved in sexual reproductionAre not directly involved in sexual reproduction Often are used in asexual forms of reproduction Often are used in asexual forms of reproduction

such as cuttings, budding, or graftingsuch as cuttings, budding, or grafting

RootsRoots

Root systems have a pronounced effect on Root systems have a pronounced effect on Plant size and vigor Plant size and vigor Method of propagation Method of propagation Adaptation to soil typesAdaptation to soil types Response to cultural practices and irrigationResponse to cultural practices and irrigation

Originate from the lower portion of a plant or Originate from the lower portion of a plant or cuttingcutting

They have a root cap, but lack nodes and They have a root cap, but lack nodes and never bear leaves or flowers directlynever bear leaves or flowers directly

RootsRoots

Principal functions are to Principal functions are to Absorb nutrients and moistureAbsorb nutrients and moisture Anchor the plant in the soilAnchor the plant in the soil Support the stemSupport the stem Store foodStore food

Internal Root StructureInternal Root Structure

Internally, there are three Internally, there are three major parts of a rootmajor parts of a root MeristemMeristem is at the tip and is at the tip and

manufactures new cells; it is an manufactures new cells; it is an area of cell division and growtharea of cell division and growth

Zone of elongation Zone of elongation cells cells increase in size through food and increase in size through food and water absorption. As they grow, water absorption. As they grow, they push the root through the they push the root through the soilsoil

Zone of maturationZone of maturation is directly is directly beneath the stem. Here, cells beneath the stem. Here, cells become specific tissues such as become specific tissues such as epidermis, cortex, or vascular epidermis, cortex, or vascular tissuetissue

Cross Section of a RootCross Section of a Root

EpidermisEpidermis the outermost the outermost layer of cells layer of cells Responsible for absorbing Responsible for absorbing

water and minerals dissolved in water and minerals dissolved in waterwater

Vascular tissue is located in Vascular tissue is located in the center of the root and the center of the root and conducts food and waterconducts food and water

CortexCortex cells move water cells move water from the epidermis to the from the epidermis to the vascular tissuevascular tissue (xylem and (xylem and phloem) and store food phloem) and store food

External Root StructureExternal Root Structure

Externally, there are two major parts of a root: Externally, there are two major parts of a root: Root cap Root cap

The outermost tipThe outermost tip Consists of cells that are sloughed off as the root grows Consists of cells that are sloughed off as the root grows

through the soilthrough the soil Function is to protect the root meristemFunction is to protect the root meristem

Root hairsRoot hairs Delicate, elongated epidermal cells that occur in a small zone Delicate, elongated epidermal cells that occur in a small zone

just behind the root's growing tipjust behind the root's growing tip Function is to increase the root's surface area and absorptive Function is to increase the root's surface area and absorptive

capacitycapacity Live 1 or 2 daysLive 1 or 2 days Transplants, tear off or dry out in the sunTransplants, tear off or dry out in the sun

Root RelationshipsRoot Relationships

Many roots have a naturally occurring Many roots have a naturally occurring symbioticsymbiotic (mutually beneficial) (mutually beneficial) relationship with certain fungirelationship with certain fungi

Improve the plant's ability to absorb water Improve the plant's ability to absorb water and nutrientsand nutrients

Is called Is called mycorrhizaemycorrhizae (fungus + root) (fungus + root)

Types of RootsTypes of Roots

TTwo major types of roots: wo major types of roots: PrimaryPrimary

Originates at the lower end of a seedling's Originates at the lower end of a seedling's embryoembryo

LateralLateral Secondary root is a side or branch root that Secondary root is a side or branch root that

arises from another rootarises from another root

Primary RootsPrimary Roots

TaprootTaproot If the primary root continues to elongate If the primary root continues to elongate

downward, becomes the central feature of the downward, becomes the central feature of the root system, and has limited secondary root system, and has limited secondary branchingbranching

Hickory, pecan trees, and carrotsHickory, pecan trees, and carrots

Lateral RootsLateral Roots

Fibrous rootFibrous root Primary root ceases to elongate, and numerous Primary root ceases to elongate, and numerous

lateral roots developlateral roots develop

Branch repeatedly to form the network of Branch repeatedly to form the network of feeding roots found on most plantsfeeding roots found on most plants

How Roots GrowHow Roots Grow

During early development, a seedling absorbs nutrients During early development, a seedling absorbs nutrients and moisture from the soil around the sprouting seed. and moisture from the soil around the sprouting seed. A band of fertilizer several inches to each side and A band of fertilizer several inches to each side and slightly below newly planted seeds helps early growth slightly below newly planted seeds helps early growth of most row crops.of most row crops.

As a plant becomes well established, the quantity and As a plant becomes well established, the quantity and distribution of its roots strongly influence its ability to distribution of its roots strongly influence its ability to absorb moisture and nutrients. For most plants, the absorb moisture and nutrients. For most plants, the majority of the absorbing (feeder) roots are located in majority of the absorbing (feeder) roots are located in the top 12 inches of soil. the top 12 inches of soil.

The soil environment in this region generally is best for The soil environment in this region generally is best for root growth, with a good balance of fertility, moisture, root growth, with a good balance of fertility, moisture, and air spaces.and air spaces.

Factors Influencing Root Factors Influencing Root GrowthGrowth

Do not grow well water-saturated soil and die Do not grow well water-saturated soil and die due to lack of oxygen (wet feet)due to lack of oxygen (wet feet)

Penetrate deeper in loose, well-drained soilPenetrate deeper in loose, well-drained soil A dense, compacted soil layer can restrict root A dense, compacted soil layer can restrict root

growth growth Roots grow laterally and often extend well Roots grow laterally and often extend well

beyond a plant's driplinebeyond a plant's dripline High salinity can restrict root growthHigh salinity can restrict root growth Roots don’t seek out a healthy environment, Roots don’t seek out a healthy environment,

but they thrive in onebut they thrive in one

Roots as FoodRoots as Food

An enlarged root is the edible portion of An enlarged root is the edible portion of several vegetable crops several vegetable crops Sweet potatoes are a swollen tuberous root Sweet potatoes are a swollen tuberous root Carrots, parsnips and radishes are Carrots, parsnips and radishes are

elongated taproots elongated taproots