Study On Effects Of Boron On Growth And Development Of Mung Bean (Phaseolus Aureus Roxb.)

Boron deficiency is a widespread nutritional disorder of plants throughout the world and causes a wide variety of adverse symptoms. However the primary role of boronhas been remained unknown. Many hypotheses on the function of boron have been advancedbased on the effects of boron on a single organ of plant. The current study aimed to evaluatethe role of boron in regard to various effects on shoot growth and development in mung bean(Phaseolus aureus Roxb.). An effort has also made to analyse the relationships of differentphysiological processes when boron is deficient.Growth analysis indicated that boron limitation inhibited growth of all parts of the plant.Axillary buds were induced to grow in boron deficient plants. Foliar features were also alteredby boron deficiency: leaf expansion was inhibited, but there was increased leaf thickness,with a diminished specific leaf area (SLA), an increased leaf weight ratio (LWR) andinter-veinal chlorosis.More carbohydrate accumulated in boron deficient leaves, although reduced stomatalconductance and lower photosynthetic rate were notable in such leaves compared with thosein boron sufficient leaves. The inter-veinal chlorosis evidenced in the youngest leaf has beeninterpreted as a reflection of the carbohydrate accumulation measured in boron-deficientleaves. Thus inhibited growth of boron deficient plants is not due to shortage of carbohydrate.Inhibited CO2 assimilation of boron deficient leaves, a secondary effect of boron, might resultfrom negative regulation of carbohydrate accumulation, caused by inhibited growth in theyoungest leaf and root and reduced intercellular air-spaces, all of which may relate to the roleof boron in cell walls. Much carbohydrate accumulation and inhibited cell expansion resultedin the inhibited SLA and LWR of boron deficient leaves.The implications of deficient symptoms and physiological and biochemical alterationsare discussed. All of these adverse effects may originate from damaged cell walls when boronis deficient. The work presented here fits the hypothesis that the primary role of boron relatesto cell wall structure and properties.