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| The Shoot System |
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| Shoot is the ascending portion of the axis and develops from the plumule of the embryo. It consists of the main axis or stem, branches and leaves. The stem is provided with nodes and internodes which may not be distinct in all cases. Leaves and branches develop from the nodes. The portion between two successive nodes is called an internode. The terminal or apical bud lies at the apex of the stem whereas the axillary bud is present in the axil of a leaf and the stem. |
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| fig. 27.11 Forms of Stem |
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 The stem gives support to the branches and leaves. |
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 It helps in the upward conduction of water and mineral salts and downward conduction of prepared food material. |
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 When the plant matures, the stem and the branches take part in the formation of reproductive structures (flowers). |
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 The underground modified stems serve to store food materials. |
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 The underground stems and a few aerial stems take part in vegetative reproduction. |
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| In most of the plants, the stem is aerial and in a few plants the stem is underground. The aerial stem may be erect or weak. |
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| In most of the plants the stem is strong and erect. e.g., Coconut |
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| In some plants, the stem is weak. Such plants may be classified into trailers, creepers and climbers. |
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| fig. 27.12 -Types of Weak Stems |
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| Trailers |
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| These are plants with a weak stem trailing on the ground without rooting at the nodes. They may be classified into prostrate, or procumbent and decumbent trailers. |
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 In prostrate or procumbent trailers, the stem lies prostrate on the ground (e.g., Portulaca). |
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 In decumbent trailers, the stem after trailing on the ground for some distance tends to rise at the apex (e.g. Tridax). |
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| Creepers |
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| In some plants, the stem is weak and creeps on the surface of the soil. The creeping stem produces roots at the nodal regions (e.g. Oxalis). |
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| Climbers |
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| In some plants the weak stem climbs on the neighbouring objects with some special devices. Such plants are known as climbers (e.g., Pea). |
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| Following types of climbers can be recognised: |
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 Rootlet Climbers: These climb with the help of aerial adventitious roots developed at the nodes, as in betel, pepper, Pothos and Ficus repens. |
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 Hook Climbers: In Bauhinia vahlii, the axillary buds get modified into curved watch-spring like hooks. With the help of these hooks, the plant is able to climb. |
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| In Artabotrys, hooks are found opposite the leaves. These hooks are modified peduncles or pedicels. |
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 Tendril Climbers: Tendrils are slender, spirally coiled, spring like structures. They are highly sensitive to contact and coil around the neighbouring support. |
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| In Passiflora, the axillary bud instead of developing into a branch, gets transformed into a tendril. |
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 Leaf Climbers: In Gloriosa, the tip of the leaf gets enlongated and serves as a tendril and the plant is hence called a leaf climber. |
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 Stem Climbers or Twiners: These plants have long and slender stems with branches. They climb by twining bodily around trees and shrubs. (e.g., Ipomoea). |
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 Lianas: These are woody perennial climbers, commonly seen in tropical forests. e.g., Entada phaseoloides. |
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| fig. 27.13 Branching of the Stem |
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| The pattern of development of branches on the stem is known as branching. There are two types of branching namely, lateral and dichotomous. |
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| When the branches arise from the sides of the stem the branching is called Lateral. |
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| fig. 27.14 Lateral Branching |
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| It is divisible into two types: |
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| Racemose or Monopodial or Indefinite Type |
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| e.g. Casurina, Polyalthia etc. |
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| Here the stem indefinitely grows by the terminal bud. The lateral branches of the main stem are arranged in an acropetal succession (produced successively towards the apex with older branches towards the base and younger ones towards the apex). As a result of this branching the plant appears conical or pyramidal in shape. |
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| Cymose or Definite Type |
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| Here the growth of the main stem is definite. The main stem produces lateral branches which grow more vigorously than the main axis. As a result of this branching, the plant spreads out above and becomes more or less dome shaped. The cymose branching is of the following kinds. |
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| Uniparous Cyme |
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| A cymose type of branching with only one lateral branch produced at a time. It is also known as monochasial or sympodial. It shows two distinct types namely helicoid and scorpioid. |
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| In Saraca the branching is described helicoid. Here, the lateral branches develop on the same side forming a helix. In Vitis vinifera the branching is described as scorpioid. Here the lateral branches develop on alternate sides forming a zigzag. |
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| Biparous Cyme |
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| When two lateral branches, develop at a time the branching is said to be biparous or dichasial. Eg. Datura carissa. |
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| Multiparous Cyme |
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| When more than two branches develop at a time the branching is said to be multiparous or polychasial. Eg. Euphorbia, Croton bonplandianum. |
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| fig. 27.15 Patterns of Branching in Stem |
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| fig. 27.16 - Cymose or Definite Type |
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| In a few angiosperms, two branches are produced in forked manner. |
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