Response of Root Branching and Shoot Water Potentials of French Beans (Phaseolus vulgaris L.) to Soil Moisture and Fertilizer Potassium

Abstract

AbstractExtensive branching patterns of roots and the maintenance of adequate water within shoots enables plants to overcome water stress. However, information on the relationship between fertilizer potassium, root branching patterns and shoot water potentials of food legumes grown under different soil moisture regimes is scarce. Thus, an experiment was conducted in a phytotron to ascertain the effect of fertilizer potassium on root branching patterns and shoot water potentials of a popular tropical food legumes (Frenchbeans Phaseolus vulgaris L). The plants were grown in a sand medium with 0.1, 0.8 or 3.0 mM of potassium under a suboptimal and optima) soil moisture regime.Root lengths and dry weights were enhanced by potassium, especially under a suboptimal soil moisture regime. The branching patterns changed due to potassium, where the numbers of second and third order roots increased under both soil moisture regimes, although the impact was greater in plants grown with low soil moisture. Plant water contents measured in terms of shoot water potential, relative water contents, rurgid weight: dry weight ratio and water uptake capacity were also increased by potassium. A positive relationship was observed between root branching patterns and water potentials with increasing potassium levels especially in plants grown under suboptimal soil moisture conditions. Shoot growth and nodulation was also promoted by potassium. The ability of plants to develop a more extensive branching pattern of roots by inducing a greater number of second and third order roots and changing the root branching habit from a herringbone to a dichotomous type to maintain a greater shoot water potential especially under low soil moisture regimes is presented.