Tag: growth and development

• 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 .

Phytochrome is responsible for absorption of red and far red light it is involved in red-far red light interconversion. Phytochrome is a photoreceptor, a pigment that plants use to detect light. It is sensitive to light in the red and far red region of the visible spectrum.

Photoblastic seeds require wavelength in the range of 660nm for the germination of seeds. Out of the two forms of phytochrome, Pr form absorbs light of 660nm wavelngth. It stimulates germination.