Question

Q.10.--- is a state of metabolic arrest of a seed that facillitates the survival during adverse environmental conditions.It is one of the adaptive mechanism seen in angiosperms.

Answer 1

Answer:

Explanation:

Seed dormancy and germination are two closely linked physiological traits that have great impacts on adaptation and survival of seed plants. Seed dormancy strengthen and germination potential are comprehensively influenced by a variety of internal factors and external environment cues. Environmental factors, such as water content, light condition, ambient temperature, and nitrogen availability, act as signal input to determine whether seeds keep in a dormant state or start to germinate. Light, temperature, and nitrogen availability are the most critical environmental factors that have profound impacts on seed dormancy and germination. However, the mechanisms underlying the regulation of seed dormancy and germination by environmental signals are still poorly understood. In this review, we summarize the current knowledge of signal transduction networks linking environmental stimulus to seed dormancy establishment, dormancy break and germination, underscoring the dominating roles of temperature, light, and nitric oxide. We review temperature, light, and nitric oxide signaling pathway separately as well as the integration of these signaling pathways with phytohormone abscisic acid (ABA) and gibberellins (GA) signaling pathway in the context of seed dormancy and germination.

Answer 2

Explanation:

$\huge\mathtt\red{Answer}$

→It is a thin and continuous layer of pollen grain which encloses the PM of a cytoplasm.

→It is made up of cellulose and pectin.

→A newly differentiate and Pollen Grain has a central nucleus and cytoplasm.