Plant Science

Plant Needs

Climate factors impact plant growth and adaptation Temperature affects the growing season of a plant

Warm season crops cannot tolerate cold temperature and typically die following the first frost

Cool season crops cannot tolerate warm weather and typically die when soil temperatures rise

Precipitation needs of a plant vary by species and determine where plants can successfully grow

Light or photoperiod refers to the amount of time a plant receives sunlight each day

Nutrients provide plants with building blocks they need to grow Nitrogen, phosphorus, and potassium are considered the

most important nutrients Greenhouse, irrigation systems, and fertilizers are tools people

can use to adjust or modify these climate factors for plants

Plant Life Cycles

Annuals: plants that complete their life cycle in 1 growing season Winter annuals are planted in fall, grow in winter, mature in

spring Ex. Wheat, oats, rye, collard, clover, snapdragon, pansy

Summer annuals are planted in spring, grow in summer, mature in fall Ex. Peanuts, tomatoes, corn, squash, petunia, begonia

Biennials: plants that live 2 growing seasons 1st season seed to maturity (dormancy stage) 2nd season reproduction to death

Ex. Cabbage, beets, carrots

Perennials: plants that live more than 2 growing seasons Deciduous perennials lose their lives during their dormant season

Ex. Oaks, sweet gums, pecans, crepe myrtle Evergreen perennials retain foliage year round

Ex. Pines, furs, hollies, boxwoods

Vegetative Plant Parts

Leaves Vital for processes such as photosynthesis,

respiration, transpiration, and energy/water storage

Stems Provides support for plant, transports water,

minerals, and nutrients, allows for gas exchange, and can store energy/water

Roots Absorb water and nutrients from soil, anchor

the plant, and can store energy

Leaf Parts

Blade: large, flat part where most of the photosynthesis occurs.

Margin: edge of the leaf.  Apex: tip of leaf. Base: part of blade that attaches to petiole (bottom of

leaf). Veins: distribute water throughout the leaf.

The way they are arranged is known as venation. Midrib: primary vein in the center of the leaf. Epidermis: the outer surface of the leaf. It holds all the

parts together and usually has a waxy coating to prevent excessive water evaporation.

Stomata: tiny holes or openings in the epidermis. Water vapor, oxygen, and carbon dioxide pass through them.

Petiole: is where the leaf is attached to the stem.

Leaves

Used to determine if plant is monocot or dicot Monocots have parallel leaf venation Dicots have palmate or pinnate venation

Classified as simple or compound Simple 1 leaf blade per petiole

Ex. Corn, oak, elm, wheat Compound 2 or more leaflets per petiole

Ex. Pecan, rose, locust

Attached in 3 basic patterns Alternate 1 leaf per node on a stem, staggered Opposite 2 leaves per node on stem Whorled 3 or more leaves per node on stem

External Stem Parts

Bud: contains undeveloped plant parts. Bud Scale: tiny leaf-like protective coverings over buds

during dormancy. Terminal Bud: large bud at end of stem. Lateral Bud: buds that will become leaves. Fruit Bud: buds that will become flowers. Node: point along stem where leaves or other stems

attach. Internode: space between 2 nodes. Leaf Scar: scar left when a leaf drops from stem. Lenticel: tiny pores along stem that allow for gas

exchange. Terminal Bud Scale Scar: ring-like scar that can be found

back from the terminal bud, indicates end of growth from prior growing season.

Bark: outer skin that protects stem from injury and holds it together.

Internal Stem Parts

Xylem: tissue that transports water and minerals from roots to leaves.

Phloem: tissue that transports food from leaves to other parts of plant.

Cortex: primary stem tissue, located between bark and phloem.

Cambium: layer where growth occurs.Pith: center of stem, stores food and

moisture.

Stems

Plants are classified into 2 basic stem groups Herbaceous soft, typically have short life cycle

Ex. bedding plants Woody hard, typically have longer life cycle

Ex. trees and shrubs, perennial ornamentals

Succulents are plants that can store excess water in their stem

Aerial stems grow above groundSubterranean stems grow below ground

Tubers, bulbs, corms, rhizomes

Root Parts

Primary root: main root that all others grow off of, first to emerge from the seed.

Secondary root: branches off of the primary root.

Root hairs: small roots along primary and secondary roots that grow between soil particles and absorb water and nutrients.

Root cap: mass of cells that protect root tips as they grow.

Roots

2 main kinds of roots Taproots primary root is large and grows down

from stem Ex. Pine, carrot, dandelion

Fibrous roots roots branch at a shallow level and spread throughout the soil Ex. Corn, soybeans, tomatoes

Adventitious roots grow from stems or leaves of some climbing plants

Plant Processes

Photosynthesis Allows plants to produce their own food Carbon dioxide and water are converted to sugar

and energy when light is present and oxygen is produced as a by-product

Respiration Essentially the opposite of photosynthesis Sugars are broken down for use and energy and

carbon dioxide are releasedTranspiration

Evaporation of excess water through plant leaves and stems

Cools the plant More abundant during wet conditions

Reproductive Plant Parts

Seeds Formed in ovary of flowers 2 classifications monocots and dicots

Monocots have 1 seed leaf or cotyledon Dicots have 2 seed leaves or cotyledons

Flowers Attract pollinators Contain reproductive plant parts

Fruits Store and protect seeds 2 classifications fleshy (fibrous) and dry (pod

or hull)

Seed Parts

Seed coat: outer covering that protects embryo and holds seed together.

Hilum or Seed scar: place where seed attached to pod.

Micropyle or Silk Scar: tiny opening near hilum where sperm entered ovule during fertilization.

Endosperm: food storage compartment.Cotyledon: first leaves of a plant.Plumule: undeveloped leaf system.Epicotyl: undeveloped stem system.Radicle: undeveloped root system.

Flower Parts

Sepal: outer part of flower, usually green, found at base of petals Covers and protects bud, supports petals

Petals: attract insects for fertilizationStamen: male reproductive organ, located

inside petals Anther end of stamen, produces pollen Filament stalk that supports anther

Pistil: female reproductive organ, located in center of flower Stigma outer end with opening, often sticky to collect

pollen Style tube-like structure that connects stigma to ovary Ovary enlarged base that contains ovules

Flower Classification

Complete: have all 4 principal partsIncomplete: lack at least 1 of the

principal partsPerfect: has both stamen and pistilImperfect: lacks either a stamen or pistil

* A complete flower must be perfect, but an incomplete can be either perfect or imperfect.

Plant Reproduction

Propagation involves increasing the number of plants by using natural reproduction

Sexual propagation involves using seeds and flowers Female sex cell is the egg/ovule which is produced in

the ovary Male sex cell is the pollen which is produced by the

anther Fertilization occurs creating the seed which has a

unique genetic make-upAsexual propagation involves using vegetative

plant parts (no fertilization needed) Genetically identical offspring Seeds are not necessary to produce new offspring

Asexual Propagation Cutting (most common – wandering jew)

Remove short section of the parent plant with buds and place in growing media

Budding (fruit and nut trees, roses) Removing bud from one plant and placing it on another – must

be compatible Layering (shrubs, houseplants)

Manipulate stems so that new roots grow from stems before they are removed from parent plant

Grafting (fruit trees, roses) Place section of stem onto the stem of another plant – must be

compatible Separation (spider plant)

Structures are removed from parent plant to grow on their own

Division (ferns) Plant parts are cut into sections that will grow into larger

plants Tissue Culture (requires specialized lab)

Removing cells from parent plant to allow for many new plants

Pollination

Pollination is the transfer of pollen from the anther (male) to a stigma (female) of a flower of the same species.

Pollen is often moved by wind, insects, birds, etc.

Plants with brightly colors flowers attract insects and birds.

Flowers may be cross-pollinated or self-pollinated. Cross-pollination is when 2 different plants are

involved. Pollen from the anther of one plant is moved to the stigma of another plant.

Self-pollination involves flowers of the same plant; it is moved from one flower to another.

Fertilization

Fertilization is the union of pollen (sperm) with the ovule (egg).

Pollen grains come in contact with the stigma and are moved through the style to the ovules. The ovule then develops into a seed.

Fertilization initiates the growth of fruit and seed.

A fertilized ovary forms fruit. Once this fruit is formed the flower is no longer useful which is why many of them dry up and fall off soon after fertilization.

Seed Germination

Seed germination is the process of events where the seed embryo moves from dormancy to active growth.

It starts when the seed begins to absorb water and swell.

Primary root and stem structures emerge first.Process ends when the cotyledons start manufacturing

food.

Moisture, oxygen, temperature, humidity, planting depth, soil type, and sunlight can all impact seed germination.

Seeds are tested to determine germination rates (percent germination). This is important because it influences the number of seeds that should be planted.

Seed Treatments

Some woody plants experience dormancy and must be planted accordingly. Seed coat dormancy – some seeds have hard seed

coats that will not allow for moisture absorption. These seeds must be broken or softened through scarification without damaging the seed embryos. Ex. redbud

Embryo dormancy – some seeds embryos most go through a chilling process before they will germinate. This can be addressed by stratification – placing seeds in a moist soil medium at temperatures between 32-50° F for a certain period of time. Ex. elm

Nutrients

Essential plant nutrients help with plant growth and development. Plants will be susceptible to disease or yield low amounts of fruit without the right balance of nutrients.

Additional nutrient needs can be provided by fertilizers.

Major Plant Nutrients

Nitrogen (N) Most important Helps with leaf and stem development, plant resistance, gives

plants dark green color Phosphorus (P)

Helps with root and flower development, improves winter hardiness Potassium (K)

Second most important Aids in food transportation, thickens cell walls, disease resistance

Calcium (Ca) Increases pH, influences availability of other nutrients, cell wall

strength Magnesium (Mg)

Essential for photosynthesis and chlorophyll production Sulfur (S)

Lowers pH, root growth, protein formation

Fertilizers

Any material used to provide plants with needed nutrients.

Inorganic fertilizers include commercial formulations that are often man-made. Advantages: fast acting, proven performance, specific

nutrient composition Disadvantages: expensive, can cause environmental

problems (leaching/run-off), greater burn potential, require strict government labeling

Organic fertilizers are found in many forms include animal manure, cover crops, and processing plant waste. Advantages: slow release, low burn potential, contains

microorganisms, conditions soil Disadvantages: bulky, difficult to handle, weed seed is

likely, odor, heavy metals may be present

Why do we conduct soil tests?

To increase yields of plants. By being able to apply the needed nutrients, plants will respond favorably and yield higher quantities.

To save money. By knowing exactly which nutrients are in short supply, growers can apply just the right amount and kind of nutrients.

Tests are important to determine how much of each nutrient is available for plant growth.

What are the methods for determining nutrient shortages?

Visual inspection of the plant. This method is very unpredictable because the plant’s symptoms could be caused by something else.

Soil tests. This is probably the most widely used method. It is especially helpful when tests are taken before the crop is planted.

Tissue testing. Very accurate, but not used as extensively.

Name the nutrient levels of plants that can be divided into four levels:

Deficient: The nutrient is clearly deficient; the growth and productivity of the plant are affected. Growth response is strong once the missing nutrient is applied.

Sufficient: Just enough to satisfy plant needs. More fertilizer will increase yields only slightly.

High: Nutrient levels are high and yields are maximum. Additional nutrients would be stored in the plant. This is called luxury consumption (good when used as forage).

Toxic: Nutrient levels are too high. Yields may decline.

The kind and amount of fertilizer to use depend on several major factors.

The requirements of the crop that will be grown.

The nutrients available in the soil.Soil pH

What are the types of fertilizers?

dry fertilizerliquid fertilizergas

What do the numbers on a bag of fertilizer indicate to the user?

The nutrients that are in the fertilizerFirst number tells the percent nitrogenSecond number tells the percent

phosphorus (actually it is the percent of anhydride of phosphoric acid)

Third number tells the percent potassium (actually it is the percent potash)

When is fertilizer applied to plants?

Proper placement means it is close enough for the roots to get it but not so close that it damages the roots. pre planting applications planting applications post planting applications

top dressing side dressing

Handling fertilizer

Use only the recommended kind and amount

Apply only where it is neededStore fertilizer in dry places where

nutrients won=t be lost.Clean equipment after use.Wear protective clothing and wash after

handling or using fertilizer.Fertilizer is a chemical that can cause

reactions that are dangerous and damaging.

How do you calculate the percentage/pounds of N-P-K in fertilizer?

Example: A bag of 20-20-20 contains: 20% nitrogen or 20 pounds 20% phosphorus in the form of P2O5 or 20 pounds 20% potassium in the form of K2O or 20 pounds

The remaining 40% of the 100-pound bag is inert material.