Plant Anatomy: The Primary Plant Body

STRUCTURE AND FUNCTION OF PLANT BODY

ROOTS

A thorough knowledge of the root system of plants is essential if their growth, flowering, and fruiting responses are to be understood. The structure and growth habits of roots have a pronounced effect on the size and vigor of the plant, method of propagation, adaptation to certain soil types, and response to cultural practices and irrigation. The roots of certain vegetable crops are important as food. Roots typically originate from the lower portion of a plant or cutting. They possess a root cap, have no nodes and never bear leaves or flowers directly. The principal functions of roots are to absorb nutrients and moisture, to anchor the plant in the soil, to furnish physical support for the stem, and to serve as food storage organs. In some plants they may be used as a means of propagation.

Types of Roots
A primary (radicle) root originates at the lower end of the embryo of a seedling plant. A taproot is formed when the primary root continues to elongate downward. This makes them difficult to transplant and necessitates planting only in deep, well-drained soil. The taproot of carrot, parsnip, and salsify is the principal edible part of these crops.

A lateral, or secondary root is a side or branch root which arises from another root. A fibrous root system is one in which the primary root ceases to elongate, leading to the development of numerous lateral roots. These then branch repeatedly and form the feeding root system of the plant. A fibrous root is one which remains small in diameter because of a lack of significant cambial activity. One factor which causes shrubs and dwarf trees to remain smaller than standard trees is the lower activity rate of the cambium tissue which produces a smaller root system.

If plants that normally develop a taproot are undercut so that the taproot is severed early in the plant’s life, the root will lose its taproot characteristic and develop a fibrous root system. This is done commercially in nurseries so that trees, which naturally have tap roots, will develop a compact, fibrous root system. This allows a higher rate of transplanting success.

The quantity and distribution of plant roots is very important because these two factors have a major influence on the absorption of moisture and nutrients. The depth and spread of the roots is dependent on the inherent growth characteristics of the plant and the texture and structure of the soil. Roots will penetrate much deeper in a loose, well-drained soil than in a heavy, poorly-drained soil. A dense, compacted layer in the soil will restrict or stop root growth.

During early development, a seedling plant nutrients and moisture from the few inches of soil surrounding it. Therefore, the early growth of most horticultural crops which are seeded in rows benefits from band applications of fertilizer, placed several inches to each side and slightly below the seeds.

As plants become well-established, the root system develops laterally and usually extends far beyond the spread of the branches. For most cultivated crops roots meet and overlap between the rows. The greatest concentration of fibrous roots occurs in the top foot of soil but significant numbers of laterals may grow downward from these roots to provide an effective absorption system a couple of feet deep.

Parts of a Root
Internally, there are three major parts of a root. The meristem is at the tip and manufactures new cells. It is an area of cell division and growth. Behind it is the zone of elongation, in which cells increase in size through food and water absorption. These cells by increasing in size, push the root through the soil. The third major root part is the maturation zone, in which cells undergo changes in order to become specific tissues such as epidermis, cortex, or vascular tissue. The epidermis is the outermost layer of cells surrounding the root. These cells are responsible for the absorption of water and minerals dissolved in water. Cortex cells are involved in the movement of water from the epidermis and in food storage. A layer of suberized (a fatty material in some cells), known as the Casparian strips, has regulatory effect on the types of minerals absorbed and transported by the roots to stems and leaves.

Vascular tissues conduct food and water and are located in the center of the root. However, some monocots have the vascular system of their roots distributed around the root center.

Externally there are two areas of importance. Root hairs are found along the main root and perform much of the actual work of water and nutrient absorption. The root cap is the outermost tip of the root, and consists of cells that are sloughed off as the root grows through the soil. The root cap covers and protects the meristem and also senses gravity and directs in what direction the root grows.

Roots as Food
The enlarged root is the edible portion of several vegetable crops. The sweet potato is a swollen root, called a tuberous root, which serves as a food storage area for the plant. Carrot, parsnip, salsify, and radish are elongated taproots.

STEM

Stems are structures which support buds and leaves and serve as conduits for carrying water, minerals, and sugars. The three major internal parts of a stem are the xylem, phloem, and cambium. The xylem and phloem are the major components of a plant’s vascular system.

The vascular system transports food, water, and minerals and offers support for the plant. Xylem vessels conduct water and minerals, while phloem tubes conduct food. The vascular systems of monocots and dicots differ. While both contain xylem and phloem, they are arranged differently. In the stem of a monocot, the xylem and phloem are paired into bundles; these bundles are dispersed throughout the stem. But in the stem of a dicot, the vascular system forms rings inside the stem. The ring of phloem is near the bark or external cover of the stem and is a component of the bark in mature stems. The xylem forms the inner ring; it is the sapwood and heartwood in woody plants. The difference in the vascular system of the two groups is of practical interest to the horticulturist because certain herbicides are specific to either monocots or dicots. An example is 2, 4, -D, which only kills dicots.

The cambium is a meristem, which is a site of cell division and active growth. It is located between the xylem and phloem inside the bark of a stem and is the tissue responsible for a stem’s increase in girth, as it produces both the xylem and phloem tissues.

Stems may be long, with great distances between leaves and buds (branches of trees, runners on strawberries), or compressed, with short distances between buds or leaves (fruit spurs, crowns of strawberry plants, dandelions). Stems can be above the ground like most stems with which we are familiar, or below the ground (potatoes, tulip bulbs). All stems must have buds or leaves present to be classified as stem tissue.

An area of the stem where leaves are located is called a node. Nodes are areas of great cellular activity and growth, where auxiliary buds develop into leaves or flowers. The area between nodes is called the internode.

Parts of a Stem


The length of an internode may depend on many factors. Decreasing fertility will decrease internode length. Internode length varies with the season. Too little light will result in a long internode causing a spindly stem. This situation is known as stretch or etiolation. Growth produced early in the season has the greatest internode length. Internode length decreases as the growing season nears its end. Vigorously growing plants tend to have greater internode lengths than less vigorous plants. Internode length will vary with competition from surrounding stems or developing fruit. If the energy for a stem has to be divided between three or four stems, or if the energy is diverted into fruit growth, internode length will be shortened.

Modified Stems
Although typical stems are above-ground trunks and branches, there are modified stems which can be found above ground and below ground. The above-ground modified stems are crowns, stolons, and spurs, and the below-ground stems are bulbs, corms, rhizomes, and tubers.

A crown is a region of compressed stem tissue from which new shoots are produced, generally found near the surface of the soil. Crowns (strawberries, dandelions, African violets) are compressed stems having leaves and flowers on short internodes.

A spur is a compressed fruiting branch. Spurs are short, stubby, side stems that arise from the main stem and are common on such fruit trees as pears, apples, and cherries, where they may bear fruit. If severe pruning is done close to fruit-bearing spurs, the spurs can revert to a long, nonfruiting stem.

A stolon is a horizontal stem that is fleshy or semi-woody and lies along the top of the ground. A runner is a type of stolon. It is a specialized stem that grows on the soil surface and forms a new plant at one or more of its nodes. Strawberry runners are examples of stolons. Remember, all stems have nodes and buds or leaves. The leaves on strawberry runners are small but are located at the nodes which are easy to see. The spider plant also has stolons.

A tuber is an enlarged portion of an underground stem like potato tubers, tulip bulbs, and iris rhizomes are underground stems that store food for the plant. The tuber, like any other stem, has nodes that produce buds. The eyes of a potato are actually the nodes on the stem. Each eye contains a cluster of buds.

A rhizome is a specialized stem which grows horizontally at or just below the soil surface. They act as a storage organ and means of propagation in some plants and are similar to stolons. Some rhizomes are compressed and fleshy such as those of iris; they can also be slender with elongated internodes such as bentgrass. Johnsongrass is a hated weed principally because of the spreading capability of its rhizomes.

Tulips, lilies, daffodils, and onions are plants that produce bulbs--shortened, compressed, underground stems surrounded by fleshy scales (leaves) that envelop a central bud located at the tip of the stem. If you cut through the center of a tulip or daffodil bulb in November, you can see all the flower parts in miniature within the bulb. Many bulbs require a period of low-temperature exposure before they begin to send up the new plant. Both the temperature and length of this treatment are of critical importance to commercial growers who force bulbs for holidays.

Corms are not the same as bulbs. They have shapes similar to bulbs, but do not contain fleshy scales. A corm is a solid, swollen stem whose scales have been reduced to a dry, leaflike covering.

Some plants produce a modified stem that is referred to as a tuberous stem. Examples are tuberous begonia and cyclamen. The stem is shortened, flattened, enlarged, and underground. Buds and shoots arise from the crown and fibrous roots are found on the bottom of the tuberous stem. In addition, some plants such as the dahlia and the sweet potato produce an underground storage organ called a tuberous root, which is often confused with bulbs and tubers. However, these are roots, not stems, and have neither nodes nor internodes. It may sometimes be difficult to distinguish between roots and stems, but one sure way is to look for the presence of nodes. Stems have nodes; roots do not.

Stems are commonly used for plant propagation. Above-ground stems can be divided into sections that contain internodes and nodes. They are utilized as cuttings and will produce stems that are good propagative tissues. Rhizomes can be divided into pieces. Bulbs form small bulblets at the base of the parent bulb. Cormels are miniature corms that form under the parent corm. Tubers can be cut into pieces containing eyes and nodes. All of these will produce new plants.

Types of Stems
A shoot is a young stem with leaves present. A twig is a stem which is less than one year old and has no leaves since it is still 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. Most trees have a single trunk.

Trees are perennial woody plants, usually have one main trunk, and are usually more than 12 feet tall at maturity. Shrubs are perennial woody plants that may have one or several main stems, and are usually less than 12 feet tall at maturity.

A vine is a plant which develops long, trailing stems that grow along the ground unless they are supported by another plant or structure. Some twining vines circle their support clockwise while others circle counter clockwise. Climbing vines are supported by aerial roots, slender tendrils which encircle the supporting object, or tendrils with adhesive tips.

Texture and Growth of Stems
Woody stems contain relatively large amounts of hardened xylem tissue in its core, and are typical of most tree fruits and ornamental trees and shrubs.

A cane is a stem which has a relatively large pith and usually lives only one or two years. Examples of plants with canes include rose, grape, and blackberry.

Herbaceous or succulent stems contain only small amounts of xylem tissue and usually live for only one growing season. If the plant is perennial, it will develop new shoots from the root.

Life Cycles of Plants
Plants are classified by the number of growing seasons required to complete a life cycle. Annuals pass through their entire life cycle from seed germination to seed production in one growing season and then die.

Biennials are plants which start from seeds and produce vegetative structures and food storage organs the first season. During the first winter a hardy evergreen rosette of basal leaves persists. During the second season flowers, fruit, and seeds develop to complete the life cycle. The plant then dies. Carrots, beets, cabbage, celery, and onions are biennial plants. Hollyhock, Canterbury Bells, and Sweet William are biennials which are commonly grown for their attractive flowers.

Plants which typically develop as biennials may, in some cases, complete the cycle of growth from seed germination to seed production in only one growing season. This situation occurs when drought, variations in temperature or other climatic conditions are experienced. These cause the plant to physiologically pass through the equivalent of two growing seasons, in a single growing season. This phenomenon is referred to as bolting.

Perennial plants live for many years, and after reaching maturity, typically produce flowers and seeds each year. Perennials are classified as herbaceous if the top dies back to the ground each winter and new stems grow from the roots each spring. They are classified as woody if the top persists, as in shrubs or trees.

Stems as Food
The edible portion of cultivated plants such as asparagus and kohlrabi is an enlarged

succulent stem. The edible parts of broccoli are composed of stem tissue, flower buds, and a few small leaves. The edible part of potato is a fleshy underground stem called a tuber. Although the name suggests otherwise, the edible part of the cauliflower is proliferated stem tissue.

LEAVES

	The blade of a leaf is the expanded, thin structure on either side of the midrib. The blade is usually the largest and most conspicuous part of a leaf. The petiole is the stalk which supports the leaf blade. It varies in length and may be lacking entirely in some cases where the leaf blade is described as sessile or stalkless.
	The principal function of leaves is to absorb sunlight for the manufacturing of plant sugars in a process called photosynthesis. Leaves develop as a flattened surface in order to present a large area for efficient absorption of light energy. The leaf is supported away from the stem by a stem-like appendage called a petiole. The base of the petiole is attached to the stem at the node. The small angle formed between the petiole and the stem is called the leaf axil. An active or dormant bud or cluster of buds is usually located in the axil.
	The leaf blade is composed of several layers. On the top and bottom is a layer of thickened, tough cells called the epidermis. The primary function of the epidermis is protection of leaf tissue. The way in which the cells in the epidermis are arranged determines the texture of the leaf surface. Some leaves have hairs that are an extension of certain cells of the epidermis. The African violet has so many hairs that the leaf feels like velvet.
	Part of the epidermis is the cuticle, which is composed of a waxy substance called cutin that protects the leaf from dehydration and prevents penetration of some diseases. The amount of cutin is a direct response to sunlight, increasing with increasing light intensity. For this reason, plants grown in the shade should be moved into full sunlight gradually, over a period of a few weeks, to allow the cutin layer to increase and to protect the leaves from the shock of rapid water loss or sun scald. The waxy cutin also repels water and can shed pesticides if spreader-sticker agents or soaps are not used. This is the reason many pesticide manufacturers include some sort of spray additive to adhere to or penetrate the cuticle.
	Some epidermal cells are capable of opening and closing. These cells guard the interior of the leaf and regulate the passage of water, oxygen, and carbon dioxide through the leaf. These regulatory cells are called guard cells. They protect openings in the leaf surface called stoma. The opening and closing of the cells are determined by the weather. Conditions that would cause large water losses from plants (high temperature, low humidity) stimulate guard cells to close. Mild weather conditions leave guard cells in an open condition. Guard cells will close in the absence of light. A large percentage of stomata occur in the lower epidermis.
	The middle layer of the leaf is the mesophyll and is located between the upper and lower epidermis. This is the layer in which photosynthesis occurs. The mesophyll is divided into a dense upper layer, called the palisade layer, and a spongy lower layer that contains a great deal of air space, called the spongy mesophyll. The cells in these two layers contain chloroplasts which are the actual sites of the photosynthetic process.
	Types of Leaves A number of rather distinct types of leaves occur on plants. Leaves commonly referred to as foliage are the most common and conspicuous, and as previously stated, serve as the manufacturing centers where the photosynthetic activity of the plant occurs. Scale leaves or cataphylls are found on rhizomes and are also the small, leathery, protective leaves which enclose and protect buds. Seed leaves, or cotyledons, are modified leaves which are found on the embryonic plant and commonly serve as storage organs. Spines and tendrils, as found on barberry and pea, are specialized modified leaves which protect the plant or assist in supporting the stems. Storage leaves, as are found in bulbous plants and succulents, serve as food storage organs. Other specialized leaves include bracts, which are often brightly colored. The showy structures on dogwoods and poinsettias are bracts, not petals.
	Conifers, (pines, firs, spruce, laurel, etc.) have "needles" as leaves. They normally have waxy cuticles with sunken stomata to help deter desiccation. Also, most have resin canals on either side of the vascular system. The resin is thought to help deter and guard against insect damage.
	Venation of Leaves The vascular bundles from the stem extend through the petiole and spread out into the blade. The term venation refers to the patterns in which the veins are distributed in the blade. Two principal types of venation are parallel-veined and net-veined.
	Parallel-veined leaves are those in which there are numerous veins which run essentially parallel to each other and are connected laterally by minute, straight veinlets. Possibly the most common type of parallel-veining is that found in plants of the grass family where the veins run from the base to the apex of the leaf. Another type of parallel-venation is found in plants such as banana, calla, and pickerelweed, where the parallel veins run laterally from the midrib. Parallel-veined leaves occur on plants which are part of the monocotyledon group.
	Net-veined leaves, also called reticulate-veined, have veins which branch from the main midrib(s) and then subdivide into finer veinlets which then unite in a complicated network. This system of enmeshed veins gives the leaf more resistance to tearing than most parallel-veined leaves. Net-venation may be either pinnate or palmate. In pinnate venation, the veins extend laterally from the midrib to the edge, as in apple, cherry and peach. Palmate venation occurs in grape and maple leaves, where the principal veins extend outward, like the ribs of a fan, from the petiole near the base of the leaf blade. Net-veined leaves occur on plants which are part of the dicotyledon group.
	Leaves as a Means of Identifying Plants Leaves are useful in identifying species and varieties of horticultural plants. The shape of the leaf blade and the type of margin are of major importance as identifying characteristics. Simple leaves are those in which the leaf blade is a single continuous unit. A compound leaf is composed of several separate leaflets arising from the same petiole. A deeply lobed leaf may appear similar to a compound leaf, but if the leaflets are connected by narrow bands of blade tissue it may be classified as a simple leaf. If the leaflets have separate stalks and if these stalks are jointed at the point of union with the main leafstalk, the leaf is considered to be compound. Some leaves may be doubly compound, having divisions of the leaflets.
Apex Base Apex Base	Shape of the Leaf Blade The following are some common shapes which are found in leaves and leaflets. Linear: Narrow, several times longer than wide; approximately the same width. Elliptical: 2 or 3 times longer than wide; tapering to an acute or rounded apex and base. Ovate: Egg-shaped, basal portion wide; tapering toward the apex. Lanceolate: Longer than wide; tapering toward the apex and base. Cordate: Heart-shaped, broadly ovate; tapering to an acute apex, with the base turning in and forming a notch where the petiole is attached
	Shape of the Leaf Apex and Base The following are common shapes found in leaves. Apex Acuminate: Tapering to a long, narrow point. Acute: Ending in an acute angle, with a sharp, but not acuminate, point. Base Obtuse: Tapering to a rounded edge. Sagittate: Arrowhead-shaped, with two pointed lower lobes. Truncate: Having a relatively square end.
	Leaf Margins Studying leaf margins is especially useful in the identification of certain varieties of fruit plants. Entire: A smooth edge with no teeth or notches. Sinuate: Having a pronounced sinuous or wavy margin. Crenate: Having rounded teeth. Dentate: Having teeth ending in an acute angle, pointing outward. Serrate: Having small, sharp teeth pointing toward the apex. Incised: Margin cut into sharp, deep, irregular teeth or incisions. Lobed: Incisions extend less than halfway to the midrib. Cleft: Incisions extend more than halfway to the midrib.
	Leaf Arrangement along a Stem The various ways leaves are arranged along a stem are also used to help identify plants. Rosulate arrangement is one in which the basal leaves form a rosette around the stem with extremely short nodes. Opposite leaves are positioned across the stem from each other, two leaves at each node. Alternate or spiral leaves are arranged in alternate steps along the stem with only one leaf at each node. Whorled leaves are arranged in circles along the stem.
	Leaves as Food The leaf blade is the principal edible part of several horticultural crops including chive, collard, dandelion, endive, kale, leaf lettuce, mustard, parsley, spinach, and Swiss chard. The edible part of leek, onion, and Florence fennel is a cluster of fleshy leaf bases. The petiole of the leaf is the edible product in celery and rhubarb. In plants like Brussels sprouts, cabbage, and head lettuce, the leaves form a large, naked bud and are the edible product.

FLOWERS

	The sole function of the flower, which is generally the showiest part of the plant, is sexual reproduction. Its attractiveness and fragrance have not evolved to please man but to ensure the continuance of the plant species. Fragrance and color are devices to attract pollinators that play an important role in the reproductive process.
	Parts of the Flower As the reproductive part of the plant the flower contains the male pollen and/or the female ovule plus accessory parts such as petals, sepals, and nectar glands.
	The pistil is the female part of the plant. It is generally shaped like a bowling pin and located in the center of the flower. It consists of the stigma, style, and ovary. The stigma is located at the top, and is connected to the ovary by the style. The ovary contains the eggs which reside in the ovules. After the egg is fertilized the ovule develops into a seed.
	The stamen is the male reproductive organ. It consists of a pollen sac (anther) and a long supporting filament. This filament holds the anther in position so the pollen it contains may be disbursed by wind or carried to the stigma by insects, birds or bats.
	Sepals are small green, leaflike structures on the base of the flower which protect the flower bud. The sepals collectively are called the calyx.
	Petals are highly colored portions of the flower. They may contain perfume as well as nectar glands. The petals collectively are called the corolla. The number of petals on a flower is often used in the identification of plant families and genera. Flowers of dicots typically have sepals and/or petals in multiples of four or five. Monocots typically have these floral parts in multiples of three.
	Types of Flowers If a flower has a stamen, pistils, petals, and sepals, it is called a complete flower. If one of these parts is missing, the flower is designated incomplete. If a flower contains functional stamens and pistils, it is called a perfect flower. (Stamen and pistils are considered the essential parts of a flower.) If either of the essential parts is lacking, the flower is imperfect.
	Pistillate (female) flowers are those which possess a functional pistil(s) but lack stamens. Staminate (male) flowers contain stamens but no pistils. Because cross-fertilization combines different genetic material and produces stronger seed, cross-pollinated plants are usually more successful than self-pollinated plants. Consequently, more plants reproduce by cross-pollination than self-pollination.
	As previously mentioned, there are plants which bear only male flowers (staminate plants) or bear only female flowers (pistillate plants). Species in which the sexes are separated into staminate and pistillate plants are called dioecious. Most holly trees and pistachio trees are dioecious; therefore, to obtain berries, it is necessary to have female and male trees. Monoecious plants are those which have separate male and female flowers on the same plant. Corn plants and pecan trees are examples. Some plants bear only male flowers at the beginning of the growing season, but later develop flowers of both sexes; examples are cucumbers and squash.
	How Seeds Form Pollination is the transfer of pollen from an anther to a stigma. This may occur by wind or by pollinators. Wind-pollinated flowers lack showy floral parts and nectar since they don't need to attract a pollinator. Flowers are brightly colored or patterned and contain a fragrance or nectar when they must attract insects, animals, or birds. In the process of searching for nectar these pollinators will transfer pollen from flower to flower.
	The stigma contains a chemical which stimulates the pollen, causing it to grow a long tube down the inside of the style to the ovules inside the ovary. The sperm is released by the pollen grain and fertilization typically occurs. Fertilization is the union of the male sperm nucleus (from the pollen grain) and the female egg (in the ovule). If fertilization is successful, the ovule will develop into a seed.
	Types of Inflorescences Some plants bear only one flower per stem and are called solitary flowers. Other plants produce an inflorescence, a term which refers to a cluster of flowers and how they are arranged on a floral stem. Most inflorescences may be classified into two groups, racemes and cymes.
	In the racemose group, the florets, which are individual flowers in an inflorescence, bloom from the bottom of the stem and progress toward the top. Some examples of racemose inflorescence include spike, raceme, corymb, umbel, and head. A spike is an inflorescence in which many stemless florets are attached to an elongated flower stem or peduncle, an example being gladiolus. A raceme is similar to a spike except the florets are borne on small stems attached to the peduncle. An example of a raceme inflorescence is the snapdragon. A corymb is made up of florets whose stalks and pedicels are arranged at random along the peduncle in such a way that the florets create a flat, round top. Yarrow has a corymb inflorescence. An umbel is similar except that the pedicels all arise from one point on the peduncle. Dill has an umbel inflorescence. A head or composite inflorescence is made up of numerous stemless florets which is characteristic of daisy inflorescence.
	In the cyme group, the top floret opens first and blooms downward along the peduncle. A dischasium cyme has florets opposite each other along the peduncle. Baby’s breath inflorescence is an example. A helicoid cyme is one in which the lower florets are all on the same side of the peduncle, examples being freesia and statice inflorescences. A scorpioid cyme is one in which the florets are alternate to each other along the peduncle. Examples are tomato and potato inflorescences.

FRUIT

Parts of Fruit
Fruit consists of the fertilized and mature ovules, called seeds, and the ovary wall, which may be fleshy, as in the apple, or dry and hard as in a maple fruit. The only parts of the fruit which are genetically representative of both the male and female flowers are the seeds (mature ovules). The rest of the fruit arises from the maternal plant, and is therefore genetically identical to that parent. Some fruits have seeds enclosed within the ovary (apples, peaches, oranges, squash, cucumbers). Others have seeds that are situated on the periphery of fruit tissue (corn, strawberry).

Types of Fruit
Fruits can be classified as simple fruits, aggregate fruits or multiple fruits. Simple fruits are those which develop from a single ovary. These include cherries and peaches (drupe), pears and apples (pome), and tomatoes (berries). Tomatoes are a botanical fruit since they develop from the flower, as do squash, cucumbers, and eggplant. All of these fruits develop from a single ovary. Other types of simple fruit are dry. The fruit wall becomes papery or leathery and hard. Examples are peanut (legumes), poppy (capsule), maple (samara), and walnut (nut).

Aggregate fruits, such as raspberries come from a single flower which has many ovaries. The flower appears as a simple flower with one corolla, one calyx and one stem, but with many pistils or ovaries. The ovaries are fertilized separately and independently. If ovules are not pollinated successfully the fruit will be misshapen and imperfect. Strawberry and blackberry are also aggregate fruits with the addition of an edible, enlarged receptacle. For this reason, they are sometimes termed aggregate-accessory fruits.

Multiple fruits are derived from a tight cluster of separate, independent flowers borne on a single structure. Each flower will have its own calyx and corolla. Examples of multiple fruits are pineapple, fig and the beet seed.

SEEDS

	The seed, or matured ovule is made up of three parts. The embryo is a miniature plant in an arrested state of development. Most seeds contain a built-in food supply called the endosperm (orchid are an exception). The endosperm can be made up of proteins, carbohydrates or fats. The third part a hard outer covering called a seed coat. It protects the seed from disease and insects, and prevents water from entering the seed which would initiate the germination process before the proper time.
	Seedlings Germination is the resumption of active embryo growth. Prior to any visual signs of growth the seed must absorb water through the seed coat and micropyle. In addition, the seed must be in the proper environmental conditions; that is, exposed to oxygen, favorable temperatures, and for some correct light. The radicle is the first part of the seedling to emerge from the seed. It will develop into the primary root from which root hairs and lateral roots will develop. The portion of the seedling between the radicle and the first leaflike, (plumule), are attached to a structure called the hypocotyl which becomes the stem. The seed leaves and cotyledons encase the embryo and are usually different in shape from the leaves that the mature plant will produce. Plants producing one cotyledon fall into the group of monocotyledons or monocots. Plants producing two seed leaves are called dicotyledons or dicots.