Tag: growth and development

Phytochromes are the hormones that are light dependent and are bluish green pigments that are involved in the developmental processes. They are light dependent and activates the inactivated form of phytochrome. They sometimes are useful in seed germination and cell elongation but stops the elongation of the stem when getting too exposed to far-red light and get inactivated.

In callus culture, cell division in explant (differentiated mass of mature cells) forms and callus. Callus is an irregular unorganized and undifferentiated mass of actively dividing cells. The process is called dedifferentiation.

In plants, apical meristems divide and differentiate to perform a specific function. This phenomenon is called as differentiation. Sometimes, the differentiated cells in plants regain the capacity to divide under certain conditions. This phenomenon is called as dedifferentiation. An interfascicular vascular cambium is an example of dedifferentiation. During dedifferentiation, certain cells lose the capacity to divide and becomes mature. This phenomenon is called as redifferentiation.

Plants require four factors for its growth like:-

1. Extrinsic factors are those factors like light, water, temperature, availability of gases is the abiotic or environmental factors that control the growth of a plant. These are not controlled by the plant.
   
2. Intrinsic factors like growth regulators are released by the plant and are in direct control under the plant. They regulate process like cell differentiation, cell division etc.
   

The phonomenon of generation of whole plant by single cell is totipotency.It is the characteristic of plants mostly. When a plant of defferentiated tissue is cultured in a nutrient medium. Cells that are not dividing or are at resting stage undergo some changes and attain dividibility and become meristematic again. The process of reversion or regaining of meristematic activity to form callus is known as dedifferentiation while redefferentiation is the process in which the cell gains its specialization again.

Vivipary means that seed remains attached to the plant even during germination. It is an undesirable character for annual crops as they are not able to store under normal condition for coming years.

The phenomenon of generation of whole plant by single cell is totipotency.

• Plant growth regulators function as chemical messengers for intercellular communication. There are currently five recognized groups of plant hormones: auxins, gibberellins, cytokinins, abscisic acid ($ABA$) and ethylene.
• Indole-3-acetic acid ($IAA$, $3-IAA$) is the most common, naturally occurring plant growth regulator of the auxin class. 
  
• $2IP$ (Isopentenyl adenine) is a naturally occurring cytokinin that regulates cell division, development, and nutrient processing in plants.
• Zinc ($Zn$) is not a plant growth regulator. It is one of the eight essential micronutrients. It is needed by plants in small amounts, but yet crucial to plant development.
• So, the correct answer is '$IAA, 2IP, Zn$'.

The cells derived from root apical and shoot-apical meristems and cambium differentiate and mature to perform specific functions. This act leading to maturation is termed as differentiation. During differentiation, cells undergo few to major structural changes both in their cell walls and protoplasm. 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. For example, formation of meristems – interfascicular cambium and cork cambium from fully differentiated parenchyma cells. While doing so, such meristems / tissues are able to divide and produce cells that once again lose the capacity to divide but mature to perform specific functions, i.e., get redifferentiated.