Basic Botany and Plant Physiology Written By Latif

Basic Botany and Plant Physiology Written By Latif Lighari, Ph. D Cooperative Extension Program Tennessee State University Modified for Master Gardener training & Presented by Karla Kean, UT/Montgomery County Extension Agent

What is Botany? Botany is the study of plants. An understanding of basic botany, plant physiology and the environmental factors that affect plant growth can help one gain practical knowledge of horticulture.

OUTLINE Introduction Plant Parts and Functions Plant Growth and Development Environmental factors affecting plant growth.

INTRODUCTION All flowering plants have certain structure and functions in common. There also common responses to environmental conditions. This unit looks at what most plants have in common, some differences between plants, and applies this information to practical gardening.

INTRODUCTION Non-vascular Plants vs. Vascular Plants Primitive, non-vascular plants, such as liverworts and mosses lack conductive tissue for the circulation of water and nutrients, and are thus confined to a moist environment. Their small size and relatively dull appearance render them of limited value in the landscape. Vascular plants, which include both flowering and non-flowering plants, are very diverse. The adaptability of their root and shoot systems have enabled them to establish and thrive in many habitats.

PLANT PARTS AND FUNCTIONS Stems Leaves Buds Roots Flowers Fruit Seeds

PRINCIPLE PARTS OF A VASCULAR PLANT

PRINCIPLE PARTS OF A VASCULAR PLANT Think of these parts as divided into two groups: reproductive and vegetative. Reproductive parts include flower buds, flowers, fruit and seed. Vegetative parts include roots, stems, leaves and leaf buds. Many vegetative parts are used in asexual or vegetative reproduction such as cuttings, grafting, layering, etc.

STEMS Support buds, flowers and leaves. Transport water, minerals and sugars through the plant. The points where leaves develop along the stem are called nodes. Area between the two nodes is called an internode.

STEMS The length of an internode depends on many factors: Vigorous growing, healthy plants tend to have longer internodes than less vigorous plants. Reduced light intensity in areas of high foliage density may increase internode length.

STEMS So, what does this mean to the gardener? Many plants root more easily at the nodes and some root only at the nodes. Short, stocky transplants are more likely to develop when plants grow in strong light, have adequate spacing, and are only moderately fertilized.

TYPES OF STEMS A Shoot is a young stem with leaves present. A Twig is a stem which is less that one year old and has no leaves, since it is in the winter dormant stage. A Branch is a stem which is more than one year old, and typically has lateral stems. A Trunk is a main stem of a woody plant. Trees typically have a single trunk, but shrubs often have multiple trunks. Vines produce long trailing stems that are sometimes able to support themselves by winding around or attaching to another plant or structure. Canes are stems that usually live only a year or two. Plants with canes include rose, grape, blackberry and raspberry.

INTERNAL STEM STRUCTURE Stems generally consist of several different types of tissue: Xylem: conducts water, nutrients, and minerals from the roots to upper areas of a plant and generally forms the wood of woody plants. Phloem: comprises much of the bark of woody plants and conducts sugars from leaves to growing points, fruits and storage areas.

INTERNAL STEM STRUCTURE Cambium: is a meristem tissue; a site of cell division and active growth. It is located between the xylem & phloem and is responsible for diameter growth. The apical meristem is responsible for stem elongation. Because xylem & phloem conduct water, nutrients, and manufactured substances throughout the plant, they are called vascular tissues.

INTERNAL STEM STRUCTURE There are two distinct arrangements of vascular tissue: Dicots and Monocots. Dicots: Have vascular tissue arranged in rings as found in most trees Monocots: Have veins arranged in bundles Corn is a typical monocot as are grasses, orchids, lilies and palms.

INTERNAL STEM STRUCTURE Most, if not all monocots lack cambium tissue between xylem & phloem tissues. This means that a mature monocot stem does not increase much in diameter. Dicots continue to increase in diameter throughout their lives.

INTERNAL STEM STRUCTURE With this knowledge of stem structure, one can understand how a rodent chewing the bark off a tree kills the tree. This information is also essential in grafting. Since only the cambium layer produces new xylem and phloem, the cambium layer of both plants must be exactly aligned if a graft is to grow.

MONOCOTS

DICOTS

STEM LIFE SPAN Plants are sometimes classified by how long they live. Annuals: produce seed, and die within a single growing season. (cantaloupe, corn, marigold etc. ) Biennials: produce vegetative structure and food storage organs the first growing season. The second season they flower, fruit, develop seed and then die. (carrots, cabbage, hollyhocks etc. )

STEM LIFE SPAN Perennials: live three or more years. Woody Perennials: have shoots & roots which survive many years, such as many trees & shrubs. Herbaceous Perennials: have shoots which die back to the ground each year like hardy hibiscus, lilies, and many wildflowers.

LEAVES Leaves are the primary organs to manufacture food for plants (like a factory). Leaves can be narrow-leaves like pine needles or broad-leaves, like all other plants The enormous diversity of leaf shapes, sizes, forms and arrangements is the result of plants adapting to conditions in a vast range of habitats.

LEAVES Leaves generally consist of: Leaf Blade Midrib Smaller veins Petiole – a branch holding the leaf

LEAVES The principle function of a leaf is to manufacture plant sugars in a process called photosynthesis (which we will discuss a bit later). An important component of photosynthesis is light. Typically, flattened leaf blades present a large area for efficient absorption of light. The vein system conducts water, sugars & other items through the leaf.

LEAVES The greatest division within leaf types lies between deciduous and evergreen foliage in trees and shrubs. Evergreen leaves are shed and replaced throughout the year. Deciduous leaves are all replaced annually, mostly falling in autumn to minimize moisture loss in winter.

LEAVES The leaf blade is comprised of several layers as illustrated. The primary function of the epidermis is to protect the inner tissues.

LEAF SHAPE & VEIN ARRANGMENT The term venation refers to the vein pattern in the leaf blade.

LEAF SHAPE & VEIN ARRANGMENT Leaves may be simple or compound in arrangement: Simple leaves consist of a single blade Compound leaves have more than one blade. Compound leaves may be palmately compound like horse chestnut, pinnately compound like a locust, or even double pinnately compound like the Kentucky Coffee Tree.

LEAF SHAPE & VEIN ARRANGMENT

LEAF ARRANGMENT Leaf arrangement is another characteristic which helps identify plants. Opposite leaves are positioned exactly across the stem from each other, with two leaves at each node. Maple, ash, dogwood Alternate leaves are arranged in steps or spiraled along the stem. Oak, willow, sycamore Whorled leaves are found in circles around the stem with 3 or more at a node. Catalpa

LEAF ARRANGMENT

BUDS Buds grow at nodes and tips of the stem A bud is a condensed form of shoot which leaves or flower parts develop. There are two types of buds: Terminal Bud Axillary or Lateral Bud

TERMINAL BUD

AXILLARY/LATERAL BUD

BUDS Axillary buds may grow into lateral branches, so when pruning it is important to make pruning cuts just above an axillary bud. It is also important that the axillary bud just below a pruning cut point in the direction you want the plant to grow, whenever possible. This bud will be the strongest new growing point and will grow in the direction it points.

BUDS

BUDS The terminal bud of many plants produces a chemical called auxin which inhibits the growth of nearby lateral or axillary buds. This is referred to as apical dominance. If the terminal bud is removed, several lateral buds may quickly begin to grow. The strongest growing bud is frequently the one nearest the end of the pruned stem. Keep this in mind when pruning….

ROOTS Absorb moisture and nutrients for the entire plant, but their functions go beyond this: Transport moisture and nutrients to the base of the stem. Anchor the plant, provide it with physical support and serve as food storage organs. In some plants, roots may be used for propagation and as food

PARTS OF A ROOT Root Cap Root Hair Root Body

FLOWER Flowers are usually the showiest part of the plant and their function is sexual reproduction. The bright color & fragrance attracts pollinators, usually insects, as well as gardeners. Since the scientific name of plants is based on flower structure, knowledge of flowers is essential to plant identification.

PARTS OF A FLOWER Sepals (Calyx) Petals (Corolla) Stamen –Anther & Filament (male part) Pistil – Stigma, style and ovary (female part)

TYPES OF FLOWERS A flower having all four parts, sepals, petals, pistil & stamens is called a complete flower. If one or more of these parts is missing, the flower is designated incomplete. Flowers containing functional stamens & pistils are called perfect flowers such as peaches or tomatoes. If either of these parts are lacking, the flower is imperfect.

FLOWERING PATTERNS Peaches & tomatoes are examples of perfect flowers. Insects, wind or contact transfers pollen from the anthers to the stigma which pollinates the flower. The pollen grows, fertilization occurs and seed develops. These plants are self pollinated.

FLOWERING PATTERNS Other plants, such as apples & pears, require pollen from a genetically different plant for fertilization to occur even if they have perfect flowers. They must be cross-pollinated, usually by wind or insects.

FLOWERING PATTERNS Monoecious plants have flowers with male parts (staminate) and female parts (pistillate) located separately on the same plant. Corn, nut trees, vine crops such as cucumber, squash etc. Dioecious plants are those which produce only male or only female flowers. Holly, ginkgo, honey locust

MALE & FEMALE FLOWERS

COMMON FLOWER INFLORESCENCES

FRUITS Fruit consists of fertilized and mature ovules called seeds and the ovary wall. Botanically, tomatoes are a fruit as are squash, cucumber, eggplant and beans. The ovary wall may be fleshy as in peach or dry and hard as maple fruit and walnuts.

FRUITS The edible portion of cantaloupe and other fleshy fruit is not affected by the pollen source. The pollen source is only significant when the seed is saved or eaten. Corn is an example. Cantaloupe does not taste like cucumbers because of cross pollination.

TYPES OF FRUITS: Fruits can be classified as: Simple Fruit: develop from a single ovary, such as cherries, peaches, apples, tomatoes, nuts, maple seed and poppies. Compound or Aggregate Fruits: develop from single flowers with many ovaries; most berries are aggregate fruits.

TYPES OF FRUITS: Multiple Fruits: are derived from a tight cluster of independent flowers borne on a single structure. Examples include pineapple, fig and beet seed which are really small, dry, manyseeded fruit.

SEEDS Seed is a reproductive part of the plant. Seeds generally have three main parts: The embryo is a partially developed plant in a dormant stage. The endosperm – a food supply (Starch). A hard seed coat

SEED GROWTH Germination is the beginning of seed growth. For germination to occur, the proper environmental conditions must exist. There must be: Moisture Oxygen Favorable temperature and, sometimes, light.

SEED GROWTH Seeds may not germinate immediately after ripening and remain dormant for a time. Some seeds are dormant because of a hard seed coat and need to be soaked in water, nicked with a file or may require cold treatment (stratification) for several weeks.

SEED GROWTH Seeds cannot germinate unless they are living and they live longer when maintained cool & dry. Reseal left-over seed packets, store in air -tight containers in a refrigerator or freezer. Seed stored properly can live several years.

PLANT GROWTH & DEVELOPMENT Photosynthesis One major difference between plants & animals is that most plants can manufacture their own food (sugars) while animals cannot. To manufacture sugars, a plant requires energy from light, carbon dioxide from the air, water and a suitable temperature.

PHOTOSYTHESIS Photosynthesis literally means “to put together with light. ” Carbon dioxide + water in the presence of light = simple sugars are formed & oxygen is given off. Plants store energy from light first as simple sugars, then those may be converted to other sugars & starches & transported to storages areas.

PLANT GROWTH & DEVELOPMENT

PLANT GROWTH & DEVELOPMENT Any green plant is capable of photosynthesis; however, the leaves are the site of most sugar production because of their great surface area and specialized structures. When photosynthesis stops, plants eventually stop growing. If it stops long enough, the plant will die. Any factors required for photosynthesis (carbon dioxide, water, light, temperature) can limit this process.

PLANT GROWTH & DEVELOPMENT The importance of photosynthesis cannot be over emphasized. All plant life relies directly or indirectly on photosynthesis. All animal life feeds directly or indirectly on plants. Respiration: the process by which sugars & starches are converted into energy.

PLANT GROWTH & DEVELOPMENT PHOTOSYNTHESIS: Produces sugars Stores energy Releases oxygen Uses water Uses carbon dioxide Occurs in sunlight Occurs in chloroplasts RESPIRATION Uses sugars for energy Releases energy Uses oxygen Produces water Produces carbon dioxide Occurs in darkness & light Occurs in all cells

PLANT GROWTH & DEVELOPMENT Transpiration is the process by which a plant loses water vapor, primarily through leaf stomates. Transpiration is part of a complex system of water movement through plants. The amount of water lost depends on many environmental factors including temperature, humidity, wind, leaf thickness and shape, cuticle thickness, light intensity and plant turgor.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Temperature Is the main environmental factor affecting plant growth. Determines planting dates, growing season and what plants can be grown in a locale. Contributes to rate of plant growth and plant quality.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Hardiness Plant hardiness refers to whether a plant or plant part will survive outdoors in a given location. The chief determinant of hardiness is the degree of similarity between conditions in the garden and those in the plant’s natural habitat, especially soil type, fertility, drainage, soil and air temperature, and levels of humidity, light and rainfall.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Germination Seeds won’t grow until temperatures are within a specific range. Figure 15 in your text illustrates the variation in optimum temperature and speed of germination for some common vegetables.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Cool-Season vs. Warm Season Plants: Cool-season plants require cool temperature to germinate, grow and mature properly. They can usually withstand a considerable frost. (pansies, daffodils, peas, spinach, lettuce) Warm-season plants require warm temperatures to germinate, grow and mature properly. They are deep rooted & resistant to drought. Frost will kill or damage most warm-season crops. (zinnia, tomato, pepper, okra)

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Growth & Fruit Set Temperature is one of the factors that affects photosynthesis Extremes in temperature reduce photosynthesis and thus growth rate. Extremes in temperature can also cause bud, blossom or fruit drop in many crops such as tomatoes or peppers. This is why some plants become unproductive during summer months.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Light has 3 principle characteristics that affect plant growth: quantity, quality and duration. Quantity: Light quantity refers to the intensity or brightness. Some plants require relatively low light intensity. These plants must be placed in low light levels such as in shaded areas. Most plants grow best in full sunlight. Young plants may grow tall & leggy if the light is not bright enough for long enough.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Red & Blue light are the most effective for plant growth. Green light is reflected by plants & is the least effective. Incandescent light is generally high in red & orange light by produces too much heat to be effective as a lighting source for plants. Cool white fluorescent lights are high in blue & encourage leafy growth.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Duration Light duration or photoperiod refers to the amount of time a plant is exposed to light. It was once thought that the length of the light period triggered flowering in many plants. We now know that it is the length of uninterrupted dark period that is important.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Water Rainfall is the primary source of water for plants grown outdoors, and is vital for plant growth. Water is a primary component for: photosynthesis maintains turgor pressure transports nutrients throughout the plant.

ENVIRONMENTAL FACTORS AFFECTING PLANT GROWTH Acquisition of water: Plants acquire most of their water from the soil through root hairs. Seedlings will quickly be killed by a lack of water. Larger plants suffering from lack of water will wilt, cease growing, yellow & drop leaves, become stunted and finally die. Loss of water: Plants lose water through all their parts, but most water is lost through the leaves. This is because water loss is proportional to the surface area exposed to air. Plants reduce water loss by closing the stomates.

PLANT CLASSIFICATION & NOMENCLATURE Botanical names are preferred to common names as they are recognized internationally and apply to only one plant. Example: Family: Rosacea Genus: Rosa Species: Rosa eglanteria Subspecies: Rosa subsp. gallica Varieties: Rosa gallica var. officinalis Cultivars: Rosa “Cordon Bleu”

CONCLUSION Every plant is hardy in its natural, native habitat, since it has survived by adapting to the distinctive conditions that exist there. Flowering plants have evolved a range of strategies and structures that enable them to survive and reproduce in diverse habitats. Knowing how plants function and understanding their life cycle are vital to raising and maintaining healthy specimens.