INTRODUCTION TO BOTANY PDF

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BOTANY REVIEWER LEAVES Morphology CHARACTERISTICS • Leaves are the principle structure, produced on stems. • It is involved in vital physiological activities such as transpiration, respiration and photosynthesis. • Leaves are typically flattened and thin organs, they are adapted in many ways to thei...

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BOTANY REVIEWER LEAVES Morphology CHARACTERISTICS •

Leaves are the principle structure, produced on stems.

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It is involved in vital physiological activities such as transpiration, respiration and photosynthesis.

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Leaves are typically flattened and thin organs, they are adapted in many ways to their environment such as succulent leaves, coniferous leaves, bulb scales and some do not perform photosynthesis like spines, cataphylls and cotyledons.

PARTS OF A LEAF MONOCOT: •

Leaf sheath-the basal part of a grass leaf that encircles the stem

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Leaf blade-Extended part of leaf sheath

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Auricles- claw appendages at the base of the blade of some grasses

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Collar-a thin band of meristematic tissue at the junction of the leaf blade (lamina) and the sheath

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Ligule-outgrowth at the inner junction of the leaf sheath and blade, often membraneous, sometimes a fringe of hairs

DICOT: •

The Petiole is the stemlike part of the leaf that joins the blade to the stem. Within a petiole are tiny tubes that connect with the veins in the blade. Some of the tubes carry water into the leaf. Others carry away food that the leaf has made. In many trees and shrubs, the petioles bend in such a way that the blades receive the most sunlight, thus assuring that few leaves are shaded by other leaves. The petiole also provides a flexible "handle" that enables the blade to twist in the wind and so avoid damage.

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Leaf blades differ from one another in several ways: (1) the types of edges, (2) the patterns of the veins, and (3) the number of blades per leaf.

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Stipules – Leaf-like appendages at the base of the leaf.

Compound leaf can be of the following types based on the leaflets •

Palmately Compound Leaves - They have leaflets that diverge from the end of the petiole like the fingers off the palm of the hand.

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Pinnately Compound Leaves - Here the leaflets are arranged along the main or mid-vein.

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Bipinnately Compound Leaves - Here the leaves are twice divided and the leaflets are arranged along a secondary vein.

Based on petiole leaves are of two types •

Petiolate Leaves - They are also known as stalked leaves, these are the leaves that have a petiole. The petiole can be in different length from one plant to another.

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Sessile Leaves - These are unstalked leaves and do not possess a petiole. The lamina of the leaf expands directly from the stem.

VARIATIONS IN LEAF CONFIGURATION: VENATION •

Reticulate Venation: In this type, the veins branch and unite forming a complicated network. All the veins are interconnected, like the strands of the net.

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Parallel Venation: In this type, the veins run parallel or nearly parallel to each other and are connected by smaller veins.

PHYLLOTAXY •

Alternate - Single leaves are attached at the nodes and they alternate in direction to a greater or lesser degree along the stem.

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Opposite - They are two structures one on each opposite side of the stem, they are attached in pairs on each node.

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Whorled - Here three or more leaves attach at each node on the stem.

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Rosulate - These leaves form a rosette.

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Rows - Leaves in this type of arrangement may be alternate or opposite in their attachment but not decussate.

The basic types of leaves are •

Ferns - leaves that have fronds.

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Conifer Leaves - These are typically needle or awl or scale shaped leaves.

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Angiosperm Leaves - They are typical, standard form of leaves that includes, stipules, a petiole and a lamina.

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Sheath Leaves - They are found in most of the grasses.

TERMINOLOGIES •

RACHI-axial structure,extension of a petiole of a compound leaf that bears the leaflet

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LEAFLET-small or young foliage leaf

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PINNULE-one of the divisions of a twice pinnate leaf

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MIDRIB-central vein of a leaf

FLOWERS •

Flowers are the reproductive organs of plants.

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Flower arises from a modified leaf called bract. It consists of a very short axis on which whorls of different parts of the flower are present.

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Flower is a component of the shoot system and is the characteristic feature of angiosperms.

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Flower is responsible for the development of seed. It is the plant's reproductive structure. Sexual reproduction in plants is enabled by flowers and it is the sign of plants survival.

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Flower is a highly specialized shoot and is modified and ceased to grow to house the reproductive structures.

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They are usually bright colored to attract insects for pollination.

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Flowers that are not colorful are pollinated by wind.

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Flowers are diverse in gross appearance but the basic parts which make up the flower are basic throughout.

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The following are the recognized parts of the flower

FLORAL MORPHOLOGY •

Peduncle/Pedicel

Peduncle is the stalk of a flower. •

Receptacle

Receptacle is the stem portion, it is found at the base in the center of the flower. The internodes are short and the number of leaves is small. Hence, receptacle is not usually a large part of the flower. •

Sepals

Sepals form the outermost whorl of the floral structure. They are mostly but not always green and are leaf-like in appearance. Sepals are similar to the foliage leaves of the plant. 

Petals

Petals are present above the sepals whorl. Petals are larger than the sepals, they are brightly colored, leaf-like, broad and are thin organs. 

Corolla

is the attractive part of the flower. They provide additional protection and attract insects to facilitate pollination of the flower. 

Calyx

forms the outermost whorl of a flower. They are usually green in color and their typical function is protection for the flower in bud stage and also supports the petals when in bloom. Morphologically sepals are modified leaves. 

Perianth - compose of the calyx and corolla

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Carpels

Carpels are one or more in number and are located in the upper center of the flower. Collectively the carpels are known as gynoecium. Carpels are made of three parts: Ovary. Style and Stigma. 

Ovary is the structure present at the base of the carpel. It is an enlarged narrow region bearing one or more ovules.

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Style is the slender, neck-like portion of the carpel the leads to the ovary.

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Stigma is of variety of shapes and sizes. It present at the tip of the carpel and is sticky to collect pollen grains.

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Locule is a cell of compound ovary

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Stamens

Stamens are located inside the corolla and are leaf-like appearance. Stamens are the male part of the flower and produces pollen. Stamens consists of a filament and an anther. Stamens are collectively called androecium. •

Anther is the sac located at the tip of the filament that contains pollen.

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Filament is the stalk that connects to and holds up the anther.

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Nectaries are often associated with flowers and are found at the receptacle, nectaries produce sugary nectar which attracts insects.

Complete vs. Incomplete Flower Types Complete – Flower containing sepals, petals, stamens, and pistil Incomplete – Flower lacking sepals, petals, stamens, and/or pistils (Based on flower parts present) Perfect vs. Imperfect flower Perfect – Flowers containing male and female parts Imperfect – Flowers that lack either male or female parts

But not all incomplete flowers are imperfect because both the stamen and pistil may be present and what makes the flower incomplete is the absence of either sepal or pistil or both. Regular v. Irregular flower A regular flower is one in which all members of each set of flowering parts (stamens, pistils, petals, sepals) are alike in regard to form, orientation and colour. In irregular flowers, there are inequalities between members within the same set.. •

Bilabiate means two-lipped or double-lipped

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Orchidaceous (Orchids) - three sepals and three petals, with one petal, usually the lower one, modified to form the very different and variable lip. Stamens are reduced and united with the pistil to form the column.

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Papilionaceous (Peas or beans) - five petals of three distinct types.

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Caesalpinaceous- a large family of chiefly tropical shrubs and trees having a regular or slightly irregular corolla

Actinomorphic vs. Zygomorphic Actinomorphic- Flowers with radial symmetry In these cases, even though there may be an uneven number of sepals and petals, any line drawn through the center of the flower will divide it into two similar halves. The halves are either exact duplicates or mirror images of each other. Zygomorphic-Flowers with bilateral symmetry Flowers with irregular or bilateral symmetry have parts arranged in such a way that only one line can divide the flower into equal halves that are more or less mirror images of each other. Hypogeneous flower, Perigynous, Epigynous flower Hypogynous - sepals, petals, and stamens are attached to a convex or conical receptacle at the base of the ovary. Sepals are arranged in the outermost or lowest layer, followed by petals and stamens, with carpels or ovary innermost. The ovary is called superior and the perianth is inferior or hypogynous. EX. Lycopersicon esculentum Perigynous - sepals, petals, and sometimes stamens borne on the edge or margin of the receptacle so that they appear to form a cup around the pistil. Ex. Prunus persica Epigynous - sepals, petals, and stamens appear to arise from the top of the ovary. The concave receptacle not only surrounds the ovary, but is fused with it. In this case, the ovary is called inferior and the perianth is called superior or epigynous. Ex.Malus pumila Connation vs. Adnation Adnation-fused to an organ of a different kind, e.g. a stamen fused to a petal or an anther fused for its whole length to the filament. Connation-fused to another organ of the same kind Sympetalous

having united petals Synsepalous having united or partly united sepals Syncarpous Carpels of the gynoceum united in a compound ovary Synandrous having stamen fused along both their filaments and anthers Monocot vs. Dicot In monocots, the flower parts occur in threes or multiples of three; for example, three sepals, three petals, six stamens, and a pistil with three carpels In dicots, flower parts usually occur in fours or fives or multiples of four or five.

INFLORESCENCE Catkin – A spike with only pistillate or staminate flowers Composite or Head – A daisy-type flower composed of ray flowers (usually sterile with attractive, colored petals) around the edge and disc flowers that develop into seed in center of the flat head On some composites, the ray and disc flowers are similar Corymb – Stemlets (pedicels) arranged along main stem. Outer florets have longer pedicals than inner florets giving the display a flat top. Cyme – A determinate, flat or convex flower, with inner floret opening first. Panicle – An indeterminate flower with repeated branching. It can be made up of racemes, spikes, corymbs, or umbels. Raceme – A modification of a spike with flowers attached to a main stem ( peduncle) by stemlets (pedicel). Solitary (or single) – One flower per stem Spadix – Showy part is a bract or spathe, partially surrounding the male and female flowers inside. Spike – Flowers attached to main stem, without stemlets, bottom florets open first. Umbel – Florets with stemlets attached to main stem at one central point, forming a flat or rounded top. Outer florets open first.

Fascicle-small slender bundle POLLINATION •

Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma.

Plants can be: •

Self-pollinating - the plant can fertilize itself; or,

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Cross-pollinating - the plant needs a vector (a pollinator or the wind) to get the pollen to another flower of the same species.

TYPES OF FLOWERS BASED ON POLLINATORS •

Entomophilus-agent:insect

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Anemophilus-agent:wind

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Hydrophius-agent:water

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Zoophilus-agent:animals

GERMINATION After maturation the pollen grains enter a phase of quiescence and dry out together with the anthers. When pollen grains reach a mature stigma of the same species following pollination by wind, animals or water, they take up water. As a result the rehydrated pollen grains can reactivate and start to germinate and form a tubular extension, the pollen tube. FERTILIZATION The generative cell will divide once more to produce two sperm cells Note: plants exhibit a double fertilization); these sperm cells are thus the actual male sex cells or gametes. The division of the generative cell into a sperm cell can take place at various stages of development, in some species this division is already concluded in the anthers, in other plants it takes place in the pollen tube, shortly after the germination of the pollen grain.

FRUITS, SEEDS and GERMINATION

FRUITS •

Fruit evolves from the maturing ovary following pollination and fertilization. Fruits can be either fleshy or dry. They contain one or more seeds.

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Fruit consists of carpels where the ovules (seeds) develop and the ovary wall or pericarp, which may be fleshy (as in apples) or dry and hard (as in an acorn). Some fruits have seeds (mature ovules) enclosed within the ovary (apples, peaches, oranges, squash and cucumbers). The peel of an orange, the pea pod, the sunflower shell, and the skin flesh and pit of a peach are all derived from the pericarp.

FRUIT TYPES •

Normal fruit

develops after fertilization •

Parthenocarpic fruit

development of fruit without fertilization. The fruit resembles a normally produced fruit but is seedless. Based on Ovaries •

Simple – Fruit formed from one ovary.

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Aggregate – Fruit formed from a single flower with many ovaries. If not all of the ovaries are pollinated and fertilized, the fruit will be misshapen (raspberry, magnolia).

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Multiple – Fruit developed from a fusion of separate, independent flowers born on a single structure (mulberry, pineapple, beet seed).

Based on consistency 1. Pericarp dry and Dehiscent •

Legumes Pod (peas, beans) - Fruit from a single carpel usually splits along two sutures. Found in members of the Fabaceae (pea) family.

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Follicles (Delphinium) - Fruit from a single carpel that splits along one suture only.

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Capsule (iris, poppy, jimson weed) - Fruit from two or more carpels, each with many seeds, splitting along or between carpel lines or forming a cap that comes off or a row of pores near the top

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Silique or Silicle (mustards) - Fruits from two carpels with a central partition to which the seeds are attached. Splits to expose seeds along central membrane.

2. Pericarp dry and Indehiscent •

Achenes- Simple, one-seeded, thin-wall fruit with seed loosely attached to ovary wall.

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Caryopsis - Simple, one-seeded fruit with a thin seed coat (pericarp) surrounding and adhering tightly to the true seed

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Samara- One-seed achene fruit (elm, ash) or two-seed fruit (maple) with a wing-like structure formed from the ovary wall.

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Schizocarp- Fruit formed from two or more carpels that split at maturity to yield one-seeded halves.

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Nut - One-seeded fruit with hard stony shell (pericarp) surrounding the seed

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Pericarp Fleshy

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Berry- Fruit develops from the ovary only. Pulpy fruit from one or more carpels that develops few to many seeds, inner and outer walls fleshy.

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Hesperidium- Berries with a leather rind containing oils, enclosing a pulpy juice sack (carpels)

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Pepo- Simple fruits with relative hard rind at maturity, fleshy-watery interior with many seeds.

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Drupe- Fruit with a single seed enclosed in a hard pit. The exocarp (outer layer) becomes the thin skin; the mesocarp(middle layer) becomes thick and fleshy; and the endocarp(inner layer) becomes a hard stony pit.

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Pome- Simple fruit with several carpels and papery inner wall (endocarp) and fleshy outer wall.

SEEDS •

The seed is the outcome of sexual reproduction in flowering plants. It represents the beginning of a new generation. A seed is defined as a fertilized mature ovule that possesses an embryonic plant, stored food material and a protective coat. A seed represents a miniature plant with an adequate supply of reserve food material for nourishment of the developing embryo inside the seed.

PARTS OF A SEED (seed coat) It is protective covering of the seed and is made up of two layes: (a) outer-called Testa which is usually hard, and (b) inner-called Tegmen which is thin and papery. There is a small opening at one end of the seed coat, called micropyle through which water enters the seed. The stalk of the seed with which the seed is attached to fruit wall is called funiculus. A large scar is located near the middle of one edge, where the seed breaks from the stalk of funiculus, this is called hilum. There is a ridge beyond the hilum opposite the micropyle. It represents the base of the funiculus which is fused with the integuments and is called raphe.

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Monocot Seeds

Seed coat – From the wall of the embryo sack (mother tissue) Endosperm – Food supply containing 3 sets of chromosomes (2 from the mother and 1 from the father) 

Embryo – Immature plant

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Cotyledon – Seed leaf

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Plumule – Shoot

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Radicle/Hypocotyl– Root (remain underground)

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Dicot Seeds

Seed coat – From embryo sack wall and endosperm tissue (During development, the endosperm stops dividing and is absorbed into the embryonic tissues.) Embryo – Immature plant 

Cotyledon – Food storing seed leaf

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Plumule – Shoot

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Hypocotyl – Stem

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Radicle-Roots

SEED TYPES •

It is a food-laden tissue, either present on one side of the embryo or surrounding the embryo on all sides. In some seeds the endosperm is present until maturity. Such seeds are called endospermic (albuminous) seeds.

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In some seeds it is consumed in young stages by the developing cotyledons and such seeds do not have endosperm at maturity. Such seeds are called nonendospermic (ex-albuminous) seeds.

SEED DISPERSAL •

Animal dispersal

Some plants have barbs or other structures that get tangled in animal fur or feathers, and are then carried to new sites. Other...