Varied Mechanisms of Gas Exchange Parameters in Response to Altered Moisture Levels in Drought-Tolerant Cluster Bean [Cyamopsis Tetragonolaba (L.) Taub.] Genotypes

Abstract

An effort was made at Regional Agricultural Research Station (RARS), Rekulakunta to study the physiological attitudes of cluster bean (Cyamopsis tetragonoloba) against different water regimes such as 100%, 80%, 60%, 40%. Six cluster bean genotypes were grown in pots in a complete random block design (CRBD) and were regularly irrigated. Plants were subjected to drought treatment at 39 days after sowing (DAS) for 8 days. On the 46^th day of sowing photosynthetic rate (P_N), stomatal conductance (g_S), transpiration (E), internal CO₂ (C_i) were measured.  Intrinsic water use efficiency (WUE_i), relative water content (RWC), SPAD chlorophyll meter reading (SCMR) and specific leaf area (SLA) were determined using standard protocols.  The maximum P_N, g_S, E, and C_i were recorded at 60% water level coupled with RWC, SCMR, and SLA.  With the increased drought, genotypes showed reduced P_N, g_S, E, and C_i except in varieties RGC-1025 and RGC-936. WUE_i showed a negative correlation with P_N, g_S, E, and C_i indicating the genotypical efficiency in copping water stress.