Page 199 - PG 101-Course notes مذكرة النظري 24-25 with spec

Medicinal plants (PG 101) Level 1 Clinical Pharmacy-PharmD

Plant growth and development

A. Growth from Seeds

1. Germination

- Seed contains embryo in stage of arrested development

- germination = resumption of growth; process governed by environmental factors

and genes

- environmental factors: no. of hours of daylight, availability of water, soil

temperature, oxygen levels; example: imbibing water needed to cause seed coat

to split --> more oxygen reaches embryo to allow aerobic metabolism

- Root cells activated first (usually) --> cell division and elongation --> primary root

breaks through seed coat (= end of germination

2. Primary growth patterns

- cell division increases capacity for growth, but only about 1/2 of daughter cells

undergo enlargement

- water uptake drives cell enlargement; when plant cell enlarges, cell wall thickened

by polysaccharide deposits

- selective expression of genes results in differentiation of daughter cells and

determines specifics of subsequent growth; descendent cells divide in prsecribed

planes and expand in specific directions --> plant parts of specific shapes, functions

(e.g., leaf formation)

- plant hormones produced when some cells express genes for those hormones.

3. Early development of corn

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