Assessment of water relation traits during different phenological stages in mango (Mangifera indica L.)

Abstract

In mango, water stress plays an important role in flowering & fruiting regulation as it provides the floral induction signal. Pressure volume curve (P-V curve) was used to derive basic water relation parameters, viz., osmotic potential, symplastic and apoplastic water content, solute potential at full turgor, turgor loss point, water content at turgor loss point and elasticity modulus in plant system. In the present paper Amrapali and Langra mango cultivars having regular and irregular bearing habit, were studied in order to understand the leaf responses to different water status. The effect of paclobutrazol (PP333), a growth retardant having anti-gibberellin activity and induce the flowering even in the 'Off' year on these parameters was also studied. During flower bud differentiation (FBD), Amrapali had more osmotic potential (-3.39 MPa) than Langra (-5.38 MPa) without any significant shift with paclobutrazol treatment. However, osmotic potential increased markedly in trees treated with paclobutrazol (2 g a.i./ tree) at flower bud burst and panicle emergence stages as compared to control. Langra exhibited lower turgor loss point (-5.56 MPa) than Amrapali (-5.41 MPa) at FBD, which indicate early turgor loss in leaves of Langra than Amrapali during the critical period of flowering. Amrapali showed lower turgor loss point (TLP) in subsequent stages of flower development, which may signify that with lower TLP it may be able to maintain osmoregulation at lower leaf water potentials. Sap flow also varied significantly in these cultivars as Amrapali had higher range of sap flow (6.76-18.99 kg/h) than Langra (6.91-13.11 kg/h) in different flower developmental stages. The results of this study showed that adjustment for water stress may be greater in Amrapali than Langra sharing same habitat but having different bearing pattern. Better osmoregulation may be helpful for Amrapali to outgrow better than Langra under subtropical conditions.