Soil-plant-water relationship of boron and factors affecting its availability - A review (Part-II)
Sarfaraz Hussain Bangash
ABSTRACT
Intro: Functions of boron in plants The exact and specific function of boron in plant vegetative life is not understood as yet. However, investigations have shown that it causes death of the terminal growing point, breakdown of the conducting tissues and results in the brittleness of stem and petiole which finally causes brown coloration and cessation of roots and height-growth (Bangash & Gardiner, 1985). Boron deficiency causes increase in total sugar and starch in leaves and stems of boron deficient plant (Oram, 1961); while a greater amount of benzene insoluble matter is also found in the leaves of normal plants and in the stem of boron deficient plants. Certain parts of plants die because of lack of sugar of inadequate presence of boron. Thus boron deficiency symptoms may be an expression of sugar deficiency. Boron is essential to cell division (Haas and Klotz, 1931) in the meristematic tissue and in the cambium and is a necessary component of cell wall (Berger, 1949). It prevents excessive swellings & Plays some part in the formation of pectin. Its deficiency results in cellular swellings of the middle lemella followed by the discoloration & breakdown of cell wall as a result of boron starvation strongly indicates that boron plays definite role in the formation of pectin substances and in cell rigidity (Oram, 1961).
Boron also plays an important role in the nitrogen metabolism and consequently in the synthesis of protein in the plant tissues because nitrogen compounds and sugar accumulate while meristematic tissues dies in absence of boron (Berger, 1949). There may also be an accumulation of soluble nitrogen and carbohydrates in plants and a reduction of amount of protein formed. Its deficiency results in higher NO3-N, whereas its sufficiency decreases NO3-N in plants (Oram, 1961). Boron has an effect on pollen germination and prevents bursting of Pollen Tube, hastens flowering and fruiting process and increases seed & fruit formation, activities salt absorption, Increases seed & Fruit formation, hormone movement, metabolism of pecitc sustances, water metabolism and the water relations in plants and respiratory activities. Boron is said to be a constituent of membranes and serve in precipitating excess cations.
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