Quantitative analysis of relative growth rate based on leaf growth characteristics and evapotranspiration of eggplant and tomato under periodic water deficit at reproductive stage

Abstract: A quantitative growth analysis was performed using instantaneous leaf growth parameters for eggplant and tomato under soil water deficit conditions. A conventional approach was applied for quantifying the relative growth rate (RGR) calculation and was compared with directly measured RGR. Relative leaf growth rate (R_LA) was also measured in relation to leaf area (L_A). Total plant dry weight (L_dw) was significantly reduced under stress for both the crops and hence RGR. Total Leaf area (L_A) and leaf weight (L_dw) was higher in tomato than that of eggplant and adversely affected by periodic water deficit at reproductive stage. Water deficit lowered the leaf growth in terms of L_A and Z_dw in eggplant by 34 and 3% and in tomato by 25 and 25 %, respectively. Tomato plants showed higher CET (Cumulative evapotranspiration) by increasing water use at reproductive stages than eggplant but both plants lowered the CET underwater deficit. Among the leaf growth characteristics, leaf area ratio (LAR), specific leaf area (SLA), leaf weight ratio (LWR) and unit leaf rate (ULR) were quantified and used as important parameters for RGR analysis. The index LAR was very sensitive and had great influence on simulated RGR although it fluctuated during all growth stages. Higher SLA at reproductive stage representing lower thickness of leaf was the characteristics of eggplant. But tomato showed lower SLA that was attributed to accumulate photosynthates in leaves during reproductive stage. ULR varied during the experiment but exhibited more efficiency in tomato. In general, higher RGR at vegetative and early reproductive stages was common for both crops followed by lower RGR. The measured and calculated RGR were not constant at all at any growth stage. The calculated RGR based on leaf growth characteristics were, in general, well agreed with measured RGR for both cases indicating leaf growth characteristics credibly provides useful information for crop growth behavior. The present findings also suggest that LAR along with ULR had positive influence on RGR of eggplants and tomato at any growth stage.