SEEDBED ECOLOGY AND PROAGATION OF SOME NATURL RANGE PLANTS IN EGYPT

Abstract

The seed is an embryo or young plant in the quecent or dormant stage. It is also can be defined as the primary means by which a plant reproduces itself at a later time when conditions are suitable. Seed imbibition is the cretical first stage in the awaking up of an embryo plant. Most seeds begine to germinate soon after being planted in a moist, warm seedbed or germinating medium. James et al. (1986) summarized the major events occuring in seed germination as:water inbibition. enzyme activation. initiation of embryo growth, rupture of the seed coat and emergance of seedling. Location of seeds in the . seedbed may affect germination and seedling establishment of many plants. Environmental conditions in seedbed of the germinating seeds exert a direct and indirect influences on seed germination. Periods of stress caused by low or high temperature, drought, salinity, or other environmental factors may occur; In the course of evolution. complex defense mechanisms have been developed for protection against such stresses. One of such mechanisms is dormancy. The problem of seed dormancy is a subject of interest for many investigators. Dormancy can be attnbuted to one or more of the following causes: 1. Seed coat problems: (a) Impermeability of seed coat to water, (b) Impermeability of seed coat to gaseous exchange, (c) Seed coat anatomy. 2. Embryo problems: (a) Immaturity of embryo, (b) Viability of embryo. 3. Germination regulators: (a) Temperature requirements, (b) Light or dark requirements. (c) Excess or absence of growth regulators. (d) Occurrence of growth inhibitors.