Relationship Between Photosynthetic Carbon Exchange Rate, Specific Leaf Mass and Other Leaf Characteristics in Chickpea Genotypes

Abstract

Thirteen chickpea (Cicer arietinum L.) genotypes, raised in the field, were screened for carbon exchange rate (CER), related leaf characters and dry matter production throughout the season. Seasonal pattern of the CER and related characters were similar in all genotypes. CER showed two peaks, one at the late vegetative phase and the other at the peak pod filling phase. Stomatal resistance (r_s) and specific leaf mass (SLM) increased in the successively formed leaves while nitrogen concentration tended to decline, especially in later-formed leaves. Nitrogen (N) content per unit area, however, remained relatively constant throughout the season. Significant genotypic variabilities were observed in CER and related characters as well as in total dry matter accumulated at harvest. Seasonal means of CER ranged from 12.5 in HG 1765B to 18.4 μmol CO₂ m^-2 s^-1 in BG 315, SLM from 5.1 in HG 1765 to 6.5 mg dry weight cm^-2 in BG 315, r_s from 1.31 in BG 315 to 1.92 s cm^-1 in Hyb 16-3, leaf N content from 122.6 in HG 1765B to 172.1 mmol m^-2 in BG 315 and total dry matter at final harvest from 9.9 in HG 17658 to 34.9 g plant^-1 in K4. Seasonal means of CER were positively correlated with SLM, N content per unit area and final harvest dry matter. Stomatal resistance was negatively correlated with CER and final harvest dry matter. The results indicate that although CER is the best selection criterion for higher dry matter production in chickpea, it is possible to use SLM as an indirect selection criterion for CER in this crop. However, such a selection based on SLM involves the risk of elimination of high N-use efficiency genotypes.