BOTANY BASICS

David ShiblesMaster Gardener Coordinator

Polk County Cooperative Extension

Adapted from Botany Basics by Dr. Ann Marie VanDerZanden, Extension Master Gardener

Coordinator, Oregon State University

THE PLANT WORLD

The plant world is extremely diverse, ranging from one celled algae to huge oaks and sequoias.

It contains plants like mushrooms which have no green color.

In our gardens we find lichens and mosses, which are green plants, but have no true roots, no leaves and no flowers.

Many of us grow ferns in our gardens. They are green plants with true leaves and roots, but no flowers.

Finally there are the flowering or seed bearing plants, which make up the vast majority of plants on earth. These are the plants that we wish to discuss today.

SEED PLANTS-Spermatophyta

The seed plants are those which produce seeds, each containing an embryo (a minute, inactive plant) that germinates (begins to grow) under favorable conditions.

Seed bearing plants have true leaves, stems, roots and vascular tissue.

They consist of two classes-the Gymnospermae and Angiospermae

Gymnospermae-gymnosperms

All gymnosperms are woody, perennial, and with few exceptions evergreen. The reproductive organs are borne in structures called catkins or in cones.

Their leaves may be fern-like, scale-like, strap-shaped, or needle shaped. This group is represented primarily by cone bearing trees (conifers) and palm-like plants called cycads.

Members of this group are cypress, cycads, ginkgo, pine and cedars, podocarpus, yews and torreya.

Angiospermae

The angiosperms include those groups which have flowers and seeds always protected by a fruit.

They are broken down into two main groups the Monocotyledoncae and the Dicotyledoncae.

These divisions are determined by the number of cotyledons or “seed leaves” found in the seed.

MONOCOTS

1. Have one seed leaf.

2. Xylem and phloem are paired in bundlesand are dispersed throughout the stem.

3. The floral parts are usually in multiplesof three.

4. The leaves often have parallel veins.

DICOTS

1. Have two seed leaves.

2. The xylem and phloem are inside the stem.The ring of phloem is near the bark; thexylem forms the inner ring.

3. The floral parts are usually in multiples offour or five.

4. The leaves are usually net veined.

PLANT LIFE CYCLES

1. Annuals-completes its full life cycle in oneyear. Winter and summer annuals. Summerannuals include many flowers, crabgrass andspurge. Winter annuals include annual blue-grass and henbit.

2. Biennials-produce vegetative the firstyear, then produces seed the seconds year.Examples are Swiss chard, carrots, beets.Weeds include cudweed and bull thistle.

3. PERENNIALS - plants that live 2 years or more and are divided into herbaceous and woody perennials.

- Herbaceous perennials have soft nonwoodystems that generally die back to the ground each winter if the temperature is cold enough and new stems grow from the plants crown in the spring. Or they may just keep on growing.

- Woody perennials have woody stems that can withstand cold winter temperatures and include shrubs and trees.

PERENNIALS (con’t)

INTERNAL PLANT PARTS

Cells are the basic unit of plants. Plant reactionssuch as cell division, photosynthesis, respirationgo on at the cellular level.

Plant tissues such as meristems, xylem and phloem are large organized groups of cells thatwork together to perform specific functions.

A unique feature of plant cells is that they are totipotent

Specialized groups of cells called meristemsare the plants growing points.

EXTERNAL PLANT PARTS

Leaves, stems, roots, flowers, fruits, and seedsare known as organs. They can be divided intosexual reproductive and vegetative.

Sexual reproductive parts produce seed. They include flower buds, flowers, fruit and seed.

Vegetative parts include roots, stems, shoot buds,and leaves. They are not directly involved with sexual reproduction.

Vegetative parts can be used in asexual forms of reproduction such as cutting, budding andgrafting.

External Plant Parts-roots

Their principle functions are to absorbnutrients and moisture, anchor the plant,support the stem, and store food. They can beused for propagation in some plants. The meristematic zone manufactures new cells.

zone of maturation -cells become specifictissues-epidermis,cortex, or vasculartissue.

zone of elongation -cells increase in size andpush the root throughthe soil.

Epidermis-outermost layer which absorbs waterand nutrients.Cortex cells help move water to vascular tissueand storing food.Root cap protects the end of the root.

Root hairs are epidermal cells that occur in asmall zone behind the root’s growing tip. Theyincrease the absorptive capacity of the root. They usually live one or two days.Roots often have a symbiotic relationship with certain fungi - mycorrhizae (fungus + root).

Types of roots

1. Primary or taproot-if the primary rootelongates downward and develops few lateralroots then it is called a taproot. Examples arehickory and pecan trees and carrots.

2. Lateral root-is a side or branch root that arisesfrom another root. If the taproot ceases to grow then a fibrous root system forms.

How do roots grow - fertility, moisture andair spaces.Factors Important For Good Root Growth -1. Roots in water saturated soil may die from

lack of oxygen.2. Roots penetrate much deeper in loose, well

drained soil, than in heavy, poorly drainedsoil.

3. A dense compacted soil can restrict orterminate growth.

4. Container plants have a restricted area forgrowth and the roots may be more sensitiveto cold damage.

5. Keep in mind that plants grow downwardas well as laterally.

Vascular System-consists of xylem, phloem, and vascular cambium.

Xylem-conduct water and dissolved minerals.Phloem-carries food such as sugars.

Cambium-is a layer of meristematic tissue that separates the xylem and phloem and produces newxylem and phloem cells.

The vascular cambiumis important in grafting,because they need to lineup or the graft will fail.

Dicots-the vascular system is said to be continuousbecause it forms rings inside the stem. The ring of phloem is near the bark and eventuallybecomes part of the bark.The xylem forms the inner ring and is often calledthe sapwood and heartwood.This is important to the gardener because herbicideslike 2,4-D kill only dicots.

Roots As Food -

An enlarged root is the edible portion of severalvegetables. Sweet potatoes are a swollen tuberousroot: carrots, parsnips, salsify, and radishes areelongated taproots.

STEMS Support buds and leaves and act as aconduit for carrying water, minerals, and foodfrom photosynthesis. They may be above or belowground.

The vascular system inside the stem forms a continuous pathway from the roots to the leaves.

Stems may be long with great distances betweenleaves and buds (branches of trees) or they may compressed like crowns of strawberry plants,fruit spurs and African violets.

Above ground stems-crowns, spurs or stolons

Crowns are compressed stems with leaves andflowers on short internodes (strawberries,dandelions, and African violets).

Spurs are short, stubby side stems that arisefrom a main stem. They are the fruit bearingstems on pears, apple, cherry trees, etc.

Do not do severe pruning close to fruit-bearing spurs, because the spurs can revert back tovegetative stems.

Stolons are fleshy or semi-woody, elongated,horizontal stems that often lie on the soil surface.Leaves and roots develop from the nodes (spiderplants, St. Augustinegrass and strawberries).

Under-ground stems

Potato tubers, iris rhizomes, and tulip bulbsare underground stems that store food for theplant.

It is sometimes difficult to distinguish betweenroots and underground stems, but one sure wayis to look for nodes. Stems have nodes; rootsdo not.

Below ground stems-tubers (potatoes)

The eyes in potato tubers areactually nodes, and each eyehas a cluster of buds.

When growing potatoes fromseed pieces, it is importantthat each piece contain at leastone eye and be about the size ofa golf ball

Rhizomes resemble stolons because they growhorizontally from plant to plant. Some are fleshycompressed (iris), while others are slender andhave long internodes (bentgrass).Johnsongrass is a particularly bad rhizomonousweed.

Below ground stems -

Tulips, lilies, and onions produce bulbs, which are shortened, compressed underground stemssurrounded by fleshy scales (leaves) that envelopa central bud at the tip of the stem.

After a bulb-producing plant flowers, its phloemtransports food reserves from its leaves to the bulb’s scale. When the bulb begins growing in the spring, it utilizes the stored food. So don’t cutthe old leaves off until they have withered and died.

Bulbs are classified as tunicate and non-tunicate bulbs.

Tunicate bulbs have a thin papery coveringwhich is actually a modified leaf (narcissus, daffodilsamaryllyis, tulips and onions). This helps protect the bulb from drying out and mechanical damage.

Non-tunicate bulbs (various lilies) do not have the papery covering. They have to handled with care.

Corms are another kindof below ground stem.

Bulbs and corms are composed of the sametissue, but they are not the same.

A corm is a solid mass of stem tissue with a terminal bud on top. In additional to the terminal bud, axillary buds are produced at nodes.It is protected against injury and water loss by dry leaf bases similar to the tunic in true bulbs(gladiolus, Watsonia, Tritonia, Freesia,and African lily).

Some plants produce a modified stem called atuberous stem (tuberous begonia and cyclamen).These stems are short, flat, and enlarged. Budsand shoots arise from the crown, and fibrousroots grow from the bottom.

Other plants (dahlias and sweet potatoes) produceunderground storage organs called tuberous roots.These are often confused with bulbs and tubers,however, these are root tissue and not stem tissue.They do not have nodes or internodes.

Stems and Propagation -

Aboveground stems with nodes and internodescan be used to create new plants.

Below-ground stems are also good propagativetissue. Rhizomes can be divided into pieces,bulblets or cormels can be removed from theparent, and tubers can be cut into pieces containing eyes.

Types of plants and their stems -

Trees have one or two main trunks and are usuallytaller than 12 feet while shrubs have many main stems and are usually less than 12 feet tall. Bothhave large amounts of hardened xylem in the core.

Herbaceous or succulent stems contain lessor amounts of sapwood - may only live a year andre-grow from the crown.

Canes are stems with relatively large pith. They live only 1-2 years (roses, grapes, blackberries, and raspberries). For fruit production it is good toknow which canes to prune.

Vines-have long trailing stems.

Some vines grow along the ground while othersneed a structure to grow on. Twining vines circlea structure for support.

Some circle clockwise (hops and honeysuckle),while other circle counterclockwise (pole beansand Dutchman’s pipe).

Climbing vines are supported by either aerial roots (English ivy and poison ivy), by slendertendrils that encircle an object (cucumber, gourds, grapes, and passion flower), or by tendrilswith adhesive tips (Virginia and Japanese creeper).

Stems as food-The edible portion of several plants,such as kohlrabi, is an enlarged edible, succulentstem.

The edible parts of broccoli are composed of stemtissue, flower buds, and a few small leaves.

The edible part of a potato is a fleshy undergroundstem.

The edible part of cauliflower is actually proliferated stem tissue.

Buds-A bud is an undeveloped shoot from which leaves or flower parts grow.

Buds of many plants require a cold period before they start to grow in the spring-central Florida peaches require 250 hours (chill units) below 45 degrees).

A leaf bud is composed of a short stem withembryonic leaves. Leaf buds are often less plumpand more pointed than flower buds.

Terminal buds are located at the apex of a stem.

Lateral (auxillary) buds are located on the sidesof a stem and usually arise where a leaf meets astem (an axil).

Adventitous buds arise at sites other than theterminal or axil, such as roots, stem internode,edge of a leaf blade, or callus tissue at the end ofa stem or root.

Buds as food

Cabbage and head lettuce are unusually largeterminal buds.

Succulent axillary buds are the edible partsof Brussels sprouts.

The fleshy basal part of the flower bud’s bractis eaten in globe artichoke along with the stem.

Broccoli is probably the most important cropin Horticulture as the flower bud is eaten along with the stem and small leaves.

Leaves

Function and structureThe main function ofthe leaf is to absorbsunlight to manufactureplant sugars through photosynthesis.

A leaf is held away from the stem by a petiole and it isattached to the stem at a node. Where they meet is aleaf axil which contains a bud or buds.

Some leaves have hair-likeextensions called pubescence.

The cuticle is part of the epidermis and produces a waxy layer called cutin which protects the leaf from diseases and dehydration.

xGuard cells regulate the passage of CO2, O2 and water through tiny openings called stomata.

Types of leaves

Scale leaves-are found on rhizomes and buds,which they enclose and protect.

Seed leaves-(cotyledons) on embryonic plants.They store food for the developing seedling.

Spines and tendrils-such as those found on barberry and pea plants, protect a plant or helpsupport its stems.

Storage leaves-on bulbous and succulent plants.

Bracts-brightly colored (dogwoods and poinsettias).

Parallel veined-mostly grasses (monocots) wherethe veins run essentially parallel to each other,(base to apex) except such plants as banana, calla and pickerel-weed, whose veins run laterally fromthe midrib.

Leaf venation-monocots.

Pinnate veins-veins extend laterally from the mid-rib to the edge (apple, cherry and peach).

Palmate veins-principle veins extend outward, like the ribs of a fan (grapes and maples).

Leaf venation-dicots

Leaves shape and plant identification

lanceolate-longer than wide,tapering toward apex/base

linear-several times longer than wide-same width

cordate-heart shaped-turnsin an forms a notch wherepetiole is attached

ellipitical-2-3 x as long as wide-tapers to acute or rounded apex at base

ovate-egg shaped

entire-smooth edgecrenate-rounded teethdentate-teeth ending in anacute angle pointing outwardserrate-small sharp teeth

pointing toward the apexincised-cut into sharp

deep,irregular teethlobed-incisions extending

less than half way to midrib

Leaf edges

Leaf base shapes

Cuneate-wedge shaped; triangular with the narrow end at the point of attachment.

Obtuse-tapering to a rounded point.

Cordate- turning in and forming a notch

Leaf apex shapes

Acute-ending in an acute angle, with a sharp, but not acuminate point.

Accuminate-tapering to a long narrow point.

Obtuse-tapering to a rounded edge.

Simple leaves-the leaf blade is single continuous unit.

Compound leaves-are composed of several separateleaflets arising from the same petiole. Some leavesare doubly compound.

opposite-leaves are position across from each other.

alternate-leaves are arranged in alternate steps alongthe stem, with only one leaf at each node.

whorled-leaves are arranged in a circles along the stem.

rosulate-leaves arranged in a rosette around the stem,with extremely short internodes.

Leaves as food-the leaf blade is the principal ediblepart of several horticultural crops, including chives,collards, dandelions, endives, kale, mustard, parsley,spinach, Swiss chard and other greens.

The edible part of leeks, onions and Florence fennelis a cluster of fleshy leaf bases.

The petiole is the edible product in celery and rhubarb.

Flower Structure

Collectively the sepalsare called the calyx.

Petals may contain perfume-collectively thepetals are called the corolla.

The flower is very important for plant identification.Flowers of dicots typically have 4-5 sepals and or petals.Monocots typically come in 3’s or multiple of 3’s.

Types of flowers

If a flower has a stamen, pistil, petals and sepals,it is called a complete flower. If one of these parts is missing, then it is called an incomplete flower.

The stamen and pistal are the essential parts of a flower for seed production. If it contains bothstamens and pistal, then it is called a perfectflower.

If either the pital or stamen is missing, then it iscalled imperfect pistillate or staminate.

Plants with imperfect flowers are classified as:monoecious-have separate male and female flowers on the same plant (corn and pecan).

dioecious-species have separate male and female plants (holly, ginko, papaya and pistachio)

Types of inflorescences:

Some plants bear only one flower called a solitaryflower.

Most inflorescences belong to one of two groups-racemes and cymes. Racemes bloom from the bottom up while cymes bloom from the top down.

Pollination-is the transfer of pollen from ananther to a stigma, either by wind or by pollinators.

A chemical in the stigma stimulates pollen to grow a long tube down the style to the ovulesinside the ovary.

When the pollen reaches the ovules, it releasessperm, and fertilization typically occurs.

Cross-pollination-combines genetic material fromtwo parents.

Fruit

Fruit consists of fertilized, mature ovules (seeds)plus the ovary wall, which may be fleshy as in an apple, or dry and hard as in an acorn.

In some fruit the seeds are enclosed within theovary (apples, peaches, oranges, squash and cucumbers.

In others, the seeds are situated on the outside ofthe fruit tissue (corn and strawberries).

The only part of the fruit that has genes from bothparents is the seed. The rest is maternal.

Types of fruit

Simple-develops from a single ovary (cherries, and peaches (drupe), pears and apples (pome),and tomatoes (berry).

Tomatoes, squash, cucumbers, and eggplants alldevelop from a flower and are considered to befruits.

Other types of simple fruit are dry. There wallis either papery or leathery and hard (peanuts/legume, poppies/capsule, maples/samara, andwalnuts/nut).

Aggregate fruit-develops from a single flower withmany ovaries (strawberries, raspberries, and blackberries).

The flower is a simple flower with one corolla, onecalyx, and one stem, but it has many pistils orovaries.

Each ovary is fertilized separately. If some ovulesare not pollinated successfully, the fruit will bemisshapen.

Types of fruit

Multiple fruits are derived from a tight cluster of separate, independent flowers borne on a singlestructure.

Each flower has its own calyx and corolla.

Examples are pines, pineapples and figs.

Types of fruit

Seeds

Embryo-is a miniature plant in an arrested state ofdevelopment.Endosperm-is a built in food supply.Seed coat-hard outer covering which protects theseed from disease and water loss.

Germination

Germination is a process whereby a seed goes froma dormant state to an actively growing state.

Before this happen the seed must have water, oxygen and a favorable temperature.

Some seeds such as celery also require light, whileothers require darkness.

Radicle-is the first part of the seedling to emergefrom the seed. It develops the primary root andgrows downward.

Hypocotyl-is the structure between the radicle andthe first leaf-like structure and grows upward.

Cotyledons-encase the embryo.

Seed dormancy-because seeds are reproductivestructures, they have many mechanisms to ensuretheir survival.

There are two types of seed dormancy:

seed coat dormancy-a hard seed does not allow water to penetrate. A process called scarificationis used to break this dormancy.

embryo dormancy-these seeds must go througha chilling before they will germinate.

Other factors affecting germination:

age of the seed

seedbed preparation

planting depth

moisture

Plant Growthand Development

Photosynthesis

Respiration

Transpiration

The above 3 itemsdrive plant growth

Photosynthesis=‘s

carbon dioxide+water+sunlight=‘s Sugar+Oxygen

photosynthates-after producing carbohydrates,the plant uses them for energy, stores them, orbuilds them into complex compounds (oils/proteins).The plant uses them when light is limited or storesthem in roots or fruit.

Photosynthesis occurs in the mesophyll in chloroplasts which contain chlorophyll.

Chlorophyll is the pigment that makes leaves green.It is responsible for trapping light from the sun.

Respiration

Carbohydrates (sugars and starches) made during photosynthesis are converted to energy which the plant uses for cell growth and building new tissue.

This chemical process in which sugars and starchesare converted to energy is called oxidation and issimilar to burning wood or coal to produce heat.

Controlled oxidation in a plant is called respiration.Respiration does not depend on light so it goes onduring day and night.

Photosynthesis• produces food• stores energy• uses water• uses carbon dioxide• releases oxygen• occurs in sunlight

Respiration• uses food• releases energy• produces water• produces carbon dioxide• uses oxygen• occurs in the dark aswell as the light

Transpiration

When a leaf’s guard cell shrinks, it stomata openand water is lost. As water is lost through thestomata, more water has to be taken in throughthe roots.

Transpiration is a necessary process for plants and accounts for about 90% of the water that a plant uses. Transpiration is affected by temperature,humidity, and wind or air movement.

Transpiration is necessary for several things:

•Transporting minerals throughout the plant.

•Cooling the plant through evaporation

•Moving sugars and plant chemicals.

•Maintaining turgor pressure.

Environmental Factors Affecting Plant Growth

These factors affecting plant growth include includelight, temperature, water, humidity, and nutrition.

It is important to know how these factors affectplant growth and development.

With a basic understanding of these factors, youmay be able manipulate plants to meet your needs.

By recognizing the role of these factors, you may bebetter able to diagnose problems caused byenvironmental stress.

Light - Quality, Quantity and Duration

Quantity - refers to intensity or concentration and varies with the season.

Quality-light quality refers to the wavelength.Sunlight supplies the complete range of wavelengths.

Plants absorb blue and red light. Blue light is mainlyresponsible for vegetative growth. Red light when combined with blue light encourages flowering.

Knowing which light source to use is important toknow for manipulating plant growth.

Duration or photoperiod refers to the amount oftime the plant is exposed to light.

It was first believed that day length was the mainfactor affecting plant flowering. However, it waslater found out that it was the length of darkness.

Plants are classified into 3 day length categories:

•Short day length plants flower when they are exposed to less than 12 hr. sunlight (mums, X-mascactus, poinsettias)

• Long day plants flower when the day lengthexceeds 12 hours. This includes most summerflowering plants and vegetables.

• Day neutral plants flower regardless of daylength such as tomatoes, corn, cucumber, andsome strawberry cultivars.

• Some plants don’t fit any category, but may respond to combinations of day lengths such aspetunias.

Temperature

Generally may speed up most processes to a point.When combined with day length, it may affect the change from vegetative to reproductive.

Germination:Generally cool-season crops (spinach, radish, lettuce) germinate best at 55-65 degrees F. Warmseason crops germinate best at 65-75 degrees F.

Flowering:Sometimes day length in combination with temperature can be used to manipulate flowering.

Christmas cactus can be forced to bloom by exposing it to more than 12 hours of darkness each day and a temperature of 50-55 degrees F.

Crop quality:Low temperatures reduce energy use and increase sugar storage. Citrus is sweeter after cold weather.

Adverse temp. may cause stunted growth and poor quality. High temperatures cause bitter lettuce.

Thermoperiod - refers to daily temperature change.

Plants grow best when daytime temperature is 10 to 15 degrees higher than nighttime.

Under these conditions plant build-up and break down tissues at an optimum temperature with respiration at a nighttime minimum.

Temperatures higher than needed increases respiration sometimes greater than photosynthesis so photosynthates are used faster than they are made.

Breaking dormancy - cold period

Hardiness - ability to withstand cold. Less daylightand cooler temperatures stimulate plants toreduce photosynthesis and ship nutrients to twigs,buds, stems and roots.

Water and humidity - needed for photosynthesis,respiration, turgor pressure, solvent for nutrients,cooling factor, regulator for stomatal opening,pressure to help roots move through soil and amedium for biochemical reactions.

Plants In Communities

Ecology-interaction between plants is important for gardeners. The study of this interaction is called plant or landscape ecology.

Plant succession-as plants mature you may find that some plants will have to be replaced.

Allelopathy-when some plants produce compounds in their leaves, roots, or both that affect the growth of other plants.

Plant hormones and growth regulators-

Are chemicals (natural and synthetic) that affect flowering, aging; root growth; distortion and killing of leaves, stems and other parts; prevention and promotion of stem elongation; color enhancement of fruit; prevention of leafing and leaf fall, and many other conditions.

There are five groups of plant-growth-regulating compounds:

1. Auxins cause several responses to plants.a. bending toward a light source

(phototropism).b. downward root growth (geotropism).c. promotion of apical dominanced. flower formatione. fruit set and growthf. formation of adventitious roots

Auxin is the active ingredient in most rooting compounds.

2. Giberellins-stimulate cell division and elongation, break seed dormancy and speed germination.

3. Cytokinins-occur in both plants and animals. They promote cell division and are often used in sterile for growing plants from tissue culture. They are also used to delay aging (senescence).

4. Ethylene-it it only found in the gaseous form. It induces ripening, causes leaves to droop (epinasty) and drop (abscission), and promotes senescence.

5. Abscisic acid (ABA) is a general plant-growthinhibitor. It induces dormancy and prevents seeds from germinating; causes abscission of leaves, fruits and flowers; and causes stomata to close. High concentration of ABA in guard cells during drought stress probably play a role in closure.

THE END