لخّصلي

The Concept of Plant Growth and Development Vegetable bodies absorb water and mineral salts, accumulate solar energy, make countless reactions of substance exchange.Growth and development are two specific integrated processes of any living organism occurring simultaneously.As a result of these activities plants grow and develop.

The Concept of Plant Growth and Development
Vegetable bodies absorb water and mineral salts, accumulate solar energy, make
countless reactions of substance exchange. As a result of these activities plants
grow and develop. Growth and development are two specific integrated processes
of any living organism occurring simultaneously. Growth and development occur
throughout ontogeny (from gr. ontos “being” and genesis, “origin”) from zygote
until death. During ontogeny the hereditary information (genotype) is implemented
in strict relationship with the conditions of the environment which ultimately results
in a phenotype characteristic for the species.
Growth represents a combination of physiological and biochemical processes
through which the irreversible increase in volume, mass, size of the plants happen
due to tissue and organ expansion (Fig. 7.1).
Unlike animals, plant growth can occur throughout the life, because the centers
of growth (stem and root tips, shoots, cambium, phellogen) have active meristematic tissues that work continuously. The process of growth in plants is rhythmically interrupted by periods of rest (latency). Latency in plants is a normal
periodical phenomenon which is genetically programmed and during which a
decrease in the intensity of life processes occurs.
Growth intensity varies depending on the species, organ, environmental conditions etc. The highest rates of growth were found in mushrooms (5 mm/min) and inplants—the bamboo. Growth intensity decreases with age. Growth is determined by
a large number of genes the individual effects of which can be traced in the
phenotype even by simple measurements (with a ruler or auxanometer).
During growth new organs form which simultaneously suffer significant changes
in size, shape and structure or, in other words, growth is accompanied by development. Intensive growth occurs rather in the dark than in daylight.
Ontogenetic development is the evolution of the individual specimen from
undifferentiated cells to a mature organism and includes quantitative changes,
structural, functional changes in the properties of cells, tissues and organs (Fig. 7.2).
Development is manifested by the emergence of differentiated specialized cells
from undifferentiated embryonic cells (cytogenesis), of tissues (hystogenesis) and
organs (organogenesis) based on morphological, anatomical, physiological, biochemical changes that happen in a predefined sequence encoded by the genetic
program. Translation of the genetic information during ontogeny is performed by
differential gene expression in space and time. Development is determined by the
activity of a variety of specific proteins, whose biosynthesis and action varies
depending primarily on the gene expression levels (DNA–RNA–protein).
We can distinguish vegetative development (Fig. 7.3) and reproductive development (Fig. 7.4), which includes all fundamental processes of forming: reproductive organs—flowers, seeds and fruits (for generative propagation), as well as
specialized bodies—tubers, bulbs (for vegetative propagation). In plant morphogenesis, light is influencing growth and development through the phytochromes.