Plants Development

Definition of Development - Development is a biological process which can be defined as the process in which there is sequence of qualitative changes towards a higher or more Complex state.It consists of all the changes an organism have to undergo from the time of birth till death and in development the growth differentiation maturation and senescence take place in a regular sequence.
Development is the process which involve cell division cell maturation and cell differentiation in a sequential manner.

Leaf Development - Leaf development in plants is regulated by genes and different hormones like gibberellin. Development of leaf can be divided into three parts they are- initiation of leaf primordium, establishment of the dorsiventrality and the development of the marginal meristem.

Flower Development - Development of flower is also regulated by hormones and genes. Development of flower can be divided into three stages. They are –first the plants must be passed from the sexual immaturity stage to the sexual maturity stage. Secondly, transformation of the apical meristem from the vegetative meristems to the floral meristems take place which is known as inflorescence. Then finally the growth of the flowers individual organtake place.External stimulus is required to trigger the differentiation of the meristem into a flower meristems and this stimulus will activate mitotic cell division in the region where primordia is formed. Ball of the same stimulus is observed for the development of Meristem for follow a pattern which leads to the development of the floral meristem which is opposite to the vegetative meristems . The major difference between the meristems are verticilatephyllotaxy where the stem elongation is absent among the successive whorls or the vertices of the primordia.

Factors affecting growth and development are-

* Light - Flight controls photosynthesis transportation pigment formation tissue differentiation seed germination etc but ultraviolet rays are having inhibitory effect which induce rosette formation. Promotion of growth of plant soft organs are done by red light whereas blue light produces normal but slightly less growth. Low light intensity increases internodal length and lift size but high light intensity decreases their size but allows more development of mechanical tissue and roots. Some seeds germinate in the presence of light even some sites like lettuce and tobacco require red light for their germination also for red light counteracts the effect of red light if both are given one after the other then it is the last treatment which counts. Some other seeds like onion cannot grow in the presence of light and light induces tissue differentiation in plants which is called photomorphogenesis.

This has been observed that growing seedlings in dark produces pale and weak seedlings and this phenomenon is called etiolation and the seedlings are known as etiolated seedlings.Duration of the length of light and darkness has a profound effect on plant growth and development and this phenomenon is called photoperiodism.

* Temperature - Minimum optimum and maximum temperature for the plant growth at 2 degree centigrade to 5 degree centigrade, 20 degree centigrade to 30 degree centigrade ,40 degree centigrade to 50 degree centigrade. Preservation of articles at low temperature causes inhibition of growth of plant organs by reducing metabolic activity and non growth of pathogens. Thermoperiodicity he is having influences on seed germination growth and seasonal development of Clans Where are some plants require low temperature treatment for the growth and flowering and this phenomenon is known as vernalization.

In low temperature and in high temperature may cause injury to plants as low temperature produces desiccation chilling and freezing where else high temperature causes sun scald, leaves scorch,heat cranker and desiccation.

* Water - Optimum hydration is essential for growth and slight deficiency reduces growth and stimulates tissue differentiation.

* Oxygen - Oxygen is required for the release of energy during respiration and thus energy is needed for anabolic activities of growth.

* Soil - Soil provides minerals and some growth stimulants and water.

* Carbon dioxide - Though carbon dioxide is essential for photosynthesis that higher concentration of this gas inhibits growth.

* Hereditary potentiality - Growth and differential constitution is genetically determined by the heriditary potentiality.

* Nutrition - Nutrition is constituent of Carbohydrate protein ratio as due to high concentration of carbon and nitrogen ratio stimulus thickening of wall and less Protoplasm is formed. On the other hand is carbon nitrogen ratio is low then it favours more Protoplasm that produces thin walled soft cells.

* Growth regulators - Growth regulators are of same gibberellins cytokinins Acetic Acid phenolic inhibitors and ethylene feet regular growth and development.

Eleventh Grade

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