Tag: plant growth and development

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:-

Answer is option A i.e. "a and b only"
Light between 400-700 nm wavelength constitute the photosynthetically active radiation (PAR). Maximum absorption of light by chlorophyll a occurs in red and blue regions of the absorption spectrum. So that, the rate of photosynthesis is maximum in red and blue light of the visible spectrum.

Plant growth regulators also called as phytohormones are the plant hormones that help in the various processes of plant-like flowering, ripening of fruit etc. They are secreted in the root, shoot and include all part of the plant body and any tissue is able to release and any tissue is able to accept them and work accordingly. These are auxin, gibberellin, cytokinesis etc.

Answer is option C i.e. "Critical concentration"
The concentration of the essential element below which plant growth is retarded is termed as critical concentration. Below this minimum level, plants start to show nutrient deficiency.
While, optimum concentration is the most desirable or satisfactory level of a nutrient. Maximum concentration is the highest concentration of nutrient and nutrient toxicity occurs when excess consumption of a nutrient does harm to an organism.

Growth in plants is affected by a number of environmental factors. The most important ones are light and temperature. This is because plants are autotrophic organisms and use light energy to produce their food. Since plants are living organisms, their metabolism requires ambient temperature and pH. This is because all the metabolic reactions are catalyzed by enzymes.

The living differentiated cells that by now have lost the capacity to divide can regain the capacity of division under certain conditions. This phenomenon is termed as dedifferentiation. Example: formation of meristems - interfascicular cambium and cork cambium from fully differentiated parenchyma cells.