Tag: living organisms and their surroundings

Growth is an irreversible process. It refers to a positive change in size, often over a long period of time. It can occur as a stage of maturation or a process toward fullness or fulfillment.

Growth can be defined as an irreversible permanent increase in size of an organ or its parts or even of an individual cell. Generally, growth is accompanied by metabolic processes (both anabolic and catabolic), that occur at the expense of energy. Therefore, for example, expansion of a leaf is growth. Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. This ability of the plants is due to the presence of meristems at certain locations in their body. The cells of such meristems have the capacity to divide and self-perpetuate. The product, however,soon loses the capacity to divide and such cells make up the plant body.This form of growth where in new cells are always being added to the plant body by the activity of the meristem is called the open form of growth.

There are various plant hormones which regulate plant growth. Hormones like auxin, gibberellin, cytokinin promotes growth whereas hormones like ethylene and abscisic acid inhibits growth. Plant growth is also regulated by the climate or atmosphere. Various climatic factors like rainfall, light, temperature, humidity, etc regulates plant growth and development.

Growth is defined as the positive and irreversible change in size and mass over the period of time. It is shown by all living organisms. It occurs by an increase in cell size or number. In animals, growth is observed up to certain period of time only whereas plants shows continuous growth throughout the lifetime. 

Classical growth experiments were conducted by Darwin, Boysen-Jensen paved path to refute ancient misconceptions on plant growth. Boysen and Jensen conducted some experiments, which provided more direct evidence that transmissible substance produced in the tip participates in the response. Charles Darwin explored the inductive nature and mechanistic connection between phototropism and gravitropism.

Answer is option A i.e. "Hydrophytes"
Hydrophytes are aquatic plants that live in aquatic environments either completely or partially submerged in water. As an adaptation, their vascular tissue and mechanical tissue are reduced. The cuticle is either completely absent or it is reduced, thin and poorly developed.
On contrary, xerophytes have heavy cuticle, vascular tissue and mechanical tissue. Mesophytes have moderate vascular tissue, mechanical tissue and cuticle and epiphytes are lower plants or mosses that live in marine environment, they are non-vascular.