Tag: plant growth and development

The first sign of geotropic response occurs at a short distance away from the apex except in monocots in which case it occurs at the nodes where meristems are formed. The bending of a plant organ in response to gravity is called as gravitropism or geotropism.  Geostimulation results in rapid and marked changes in the node-puvinus, internode and sheath. These changes involves water content, dry matter accumulation, endogenous gibberellic acids and GA4 metabolism.

Chlorophyll molecules are light trapping green pigments in plants. They are made up of a cyclic tetrapyrrole head and a long phytol tail attached to the head. One atom of magnesium is directly coordinated to the four pyrrole rings in the cyclic tetrapyrrole head. Thus, magnesium is an important structural component of chlorophyll molecules. The iron is an essential micronutrient for plants. It is required for synthesis of chlorophyll and has several other functions also. Plants also require an exposure to light in order to synthesize chlorophyll.  Apparently because in the absence of light chlorophylls are not required at all; trapping of light being there chief function. In absence of light plants will be thin and pale. Such plants are called etiolated plants.

• Differentiation occurs in both external and internal features. The formation of two polar axis, i.e., differentiation of roots and shoots is the best example of external differentiation. 
• This differentiation occurs very early during embryonic development. The other example is the differentiation of the vegetative and reproductive phases.

Cambium is the layer which forms Cork and acts as a secondary meristem from a layer of collenchyma or parenchyma immediately beneath the epidermis. The cells which produce from cork cambium will differentiate and will get mature to perform a specialized function. The living cells which lost the capacity to divide can regain the capacity of the division under certain conditions is called as 'Dedifferentiation.'

 Xylem cells are dead and elongated hollow cells consists of secondary cell wall contains lignin.

Light and temperature are important for the life of plants. This paves the way for the importance of photoperiodism and vernalization in flowering plants.

Plant organs can detect a change in their orientation with respect of gravity because atleast they have to be kept for a week. When it is kept for a week, slowly changes in orientation of gravity could be sensed. This sensation is shown by them as they posses several tropic movements. Geotropism makes the changes in the plant. Shoots are negatively geotropic and roots are positively geotropic.

If a plant is flashed with red light initially and then flashed with far red light, the effect of red light is reversed. It is due to the presence of phytochromes which are present in plants as the pigments for light absorption. It has two forms, Pr and Pfr. The range of absorption in wavelength is from 660 nm to 730 nm.

In Leucosolenia, Gemmule formation (also called  internal budding ) occurs to tide over seasonal drought  or other adverse environmental conditions .