Sucrose Metabolism and RUBISCO Activity Influenced by Salicylic Acid at Flowering Stage Revealed Tolerance to Heat Stress in Chickpea Genotypes

The heat tolerant (ICC-4958, GG-2) and susceptible (ICC-4567, GJG-5) chickpea (Cicer arietinum L.) genotypes were studied for enzymes of sucrose metabolism and RUBISCO activity associated with reproductive collapse under the influence of salicylic acid (SA) during normal and late sowing. The RUBISCO (carbon fixing enzyme) and sucrose phosphate synthase (SPS) decreased significantly in tender leaves (nearer to flower) and anthers due to heat stress leading to reduced sucrose content in late sowing as compared to normal sowing in susceptible genotypes. The pollen length (SEM) of flower was reduced in susceptible genotypes correlating less sucrose and higher invertase activity under heat stress. The activities of RUBISCO, SPS and sucrose content were enhanced (4.31 and 3.29 fold) in susceptible genotypes by SA₂ (200 ppm) compared to tolerant (2.17 and 2.31 fold) in leaves under heat stress. The invertase activity remarkably decreased in tolerant genotypes compared to susceptible under the influence of SA in leaves and anthers during late sowing. The leaves sucrose content were enhanced 3.48 fold in tolerant compared to 1.55 fold in susceptible genotypes by SA₂. The improvement in reproductive failure due to heat stress (late sowing) was observed better in susceptible genotypes compared to tolerant after SA applications (200 ppm) at flowering stage which elevated enzymes of sucrose metabolism and RUBISCO activity. However, these enzymes found to be higher in tolerant genotypes as pre-existing mechanisms to boost up growth of reproductive organ. The RUBISCO activity, sucrose content and enzymes for sucrose metabolism were found higher in leaves (first tender leaves near to flower) compared to the anthers except SPS which was found higher in anthers particularly in tolerant genotypes during heat stress signifying source to sink transportation of sucrose during flower development and fertilization influenced by SA.