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Biology

PLANT GROWTH & HORMONES

PLANT GROWTH & HORMONES What is plant hornmones? Plant hormones are chemicals produced in very small amounts within the plant body, and play a very important part in regulating plant growth and development. Most growth hormones are produced at the tip of a shoot and transported downwards to the root. The root tip produces very small quantities of the hormones. Type of plant hormones What are the types of plant hormones? There are many different types of plant hormones and one well-known group is the auxins. Indoie acetic acid (IAA) is one best known auxin. Auxins Auxins are produced at the shoot and root tips.Maximum influence on growth in plants occurs when auxins are produced simultaneously with other plant hormones e.g. gibberellins. Maximum growth response in stems requires more IAA than tn roots.   Auxins are known to have various effects on the growth and development in plants. They stimulate… Read More »PLANT GROWTH & HORMONES

Biology

SEED GERMINATION: DEFINITION, TYPES, FACTORS

SEED GERMINATION: DEFINITION, TYPES, FACTORS & PROCESS What are the types of germination? The nature of germination varies in different seeds. During germination the cotyledons may be brought above the soil surface. This type of germination is called epigeal germination. If during germination the cotyledons remain underground the type of germination is known as hypogeal.   Epigeal Germination During the germination of a bean seed, the radicle grows out through the micropyle. It grows downwards into the soil as a primary root from which other roots arise. The part of the embryo between the cotyledon and the radicle is called the hypocotyl. This part curves and pushes upwards through the soil protecting the delicate shoot tip. The hypocotyls then straightens and elongates carrying with it the two cotyledons which turn green and leafy. They start manufacturing food for the growing seedling. The plumule which is lying between two cotyledons, begins… Read More »SEED GERMINATION: DEFINITION, TYPES, FACTORS

Biology

SEED GERMINATION CONDITIONS

SEED GERMINATION CONDITIONS, CONDITIONS NECESSARY FOR GERMINATION What are the conditions necessary for seed germination? Seeds can easily be destroyed by unfavourable conditions such as excessive heat, cold or animals. Seeds need certain conditions to germinate and grow. Some of these conditions are external, for example water, oxygen and suitable temperature while others are internal such as enzymes, hormones and viability of the seeds themselves.   Water A non-germinating seed contains very little water. Without water a seed cannot germinate. Water activates the enzymes and provides the medium for enzymes to act and break down the stored food into soluble form. Water hydrolyses and dissolves the food materials and is also the medium of transport of dissolved food substances through the various cells to the growing region of the radical and plumule. Besides, water softens the seed coat which can subsequently burst and facilitate the emergence of the radicle.  … Read More »SEED GERMINATION CONDITIONS

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