Tag: growth and development

Etiolation is a condition in which plant is grown in the partial or complete absence of light. The leaves are tiny and yellow in color. Vernalization is the process by which plant can be induced to flower by exposing it to the prolonged cold or winter. It shortens the vegetative period and hastens the flowering. Photoperiodism is the phenomenon in which various physiological reactions like flowering response to the relative length of day and night.

Entomophilous flowers produce an odour which many be pleasant (e.g., jasmine) or foul(e.g., Aristolochia, Arum Rafflesia). Smell and nectar attract flies and other insects.

Light is an essential factor for photosynthesis. There is a linear relationship between incident light and $CO _{2}$ fixation at low light intensities. At higher light intensities, gradually the rate does not show further increase as other factors become limiting. Light between 400-700 nm wavelength constitute the photosynthetically active radiation (PAR). Maximum photosynthesis takes place in red and blue light of the visible spectrum and minimum photosynthesis takes place in the green light. The most effective wavelength of light for photosynthesis is red because maximum absorption by chlorophyll a takes place in the red light.

Growth is an irreversible increase in the size. There are three developmental stages of growth of all plant parts including shoot and root. These are cell division, cell enlargement and cell differentiation. Cell division is the first phase that results in increase in the number of cells. In plants, karyokinesis, division of nucleus is followed by cytokinesis, the division of the cytoplasm. Cell enlargement gives the proper size to the organ and tissue. During this, protoplasm, vacuole, etc are formed. Cell differentiation is seen at cell level, tissue level, organ level and at the level of an organism. The cells differentiate to form different types of tissues that later perform different but specific functions.

Water is essential in the following ways:-