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In plants almost all cells (except the reproductive cells like gametes, zoospores etc.) are provided with a rigid wall, called cell wall. The protoplast is enclosed within the cell wall; presence of cell wall is the characteristic feature of all plant cells. The cell wall was discovered in the 17th century before the presence of protoplast was recognised, and since then the protoplast became the main object of study.
Formation of secondary wall materials on the primary wall does not take place uniformly, instead some thin areas are left out—those thin areas are called pit-fields. Thin and delicate strands or fibrils of cytoplasm, called plasmodesmata (singular: plasmodesma), pass through such pit-fields of the cell wall at intervals, thus connecting the living protoplasts of adjacent cells.
On the basis of the presence or absence of pigments, plastids are principally classified into two types, such as pigmented and non-pigmented. i.e. colourless plastids are known as leucoplasts. Pigmented i.e. coloured plastids consist of (1) chloroplasts, which are green in colour and in which the pigment chlorophyll predominates and (ii) chromoplasts, which are usually yellow, orange or red and in which pigment carotene predominates.
A cell is defined as the basic structural and functional unit of a living organism. According to Lowey and Siekevitz (1963, ‘69) cell is a "unit of biological activity delimited by a semipermeable membrane and capable of self-reproduction in a medium free of other living systems”.
What is Seed Germination? Germination is the beginning of growth and development of the dormant embryo within the seed, which consists of various changes till its final development into seedling. An embryo in a seed lies dormant i.e. showing no sign of life ; it grows into seedling after being awakened to life, this growth of embryo is not sudden but gradual which consists of a series of changes.
A fruit may be defined as a seed bearing structure produced usually after fertilization from the ovary of a flower with or without accessory parts, or from an entire inflorescence. Fruits, whether false or true, may be classified into three groups viz, (a). simple, (b) aggregate, and (c) multiple or composite.
The ovule may be defined as an immature seed or an unripened integumented megasporangium. It may also be designated simply as "the egg containing organ within ovary.” After fertilization the ovule develops into seed. In angiosperms, ovules are protected by megasporophyll which forms a closed structure (ovary), that is why seeds remain enclosed.
Anthers of a flower are composed of two anther sacs or lobes separated by a tissue called connective — each lobe or sac consists of two microsporangia separated by a septum. So in an anther there are altogether four microsporangia. Hence a fully developed anther shows quadrilocular structure.
There are two types of leaves, e.g. (a) simple and (b) compound leaves. A leaf is said to be compound when it possesses two or more articulations and the leaf blade is broken up into a number of small segments, called leaflets, due to several incisions of the blade which touch the base of the non-membranous midrib or the petiole.
Ethnobotany deals with the acquired knowledge system about the use of the biological resources among various human communities living close to nature. The term 'Ethnobotany' was first coined by Dr. John W Harshberger in 1895. It comprises two syllables. Ethno - meaning science of races and Botany - meaning science of plants.
These are the factors of habitat, which are concerned with and influenced by precipitation (rainfall, snow, dew etc), atmospheric humidity, temperature, light, velocity of wind etc. The behaviour, duration and intensity of those factors constitute the climate of a region or habitat. Some authors differentiate climatic factors into microclimate or microenvironment and macroclimate or macroenvironment.