A comprehensive model for predicting the defense system development of the most important plant: a novel approach to assess the physiological indices

Abstract

Abstract Caper is a multi-purpose halophytic plant growing in semi-arid or arid environment. The present study aims to evaluate the effect of different salt ratios of CaCl2 to NaCl on antioxidant defense system, photosynthesis pigments and morphophysiological parameters of caper under drought stress. Predictive regression modeling, principal component analysis (PCA), Pearson's correlation and path analysis were implanted to explore the possible relationships among inter correlated variables and understanding the possible mechanisms. Based on the PCA results, caper had a highest shoot and leaves growth, content of pigments, proline and antioxidant enzymes (peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase) activity and the lower leaf tissue density at the salt ratio of 1:3 (CaCl2:NaCl) under 75% FC. Predictive equation models with high significant R2 were developed for the estimation of antioxidant enzymes activity and proline content (>0.94) as well as pigments (>0.58) were developed. Path analysis studies indicated that proline is the most important regressor (significant positive effect) in four antioxidant enzymes activities while in the case of chlorophylls, leaf tissue density was the most effective variable (significant negative). It was found that caper has a better performance under moderate to high NaCl-salt stress and mild droght stress. Moreover, the network of inter correlated variables revealed that there is a close relationship between antioxidant defense system, pigments and morpholoigical parameters of caper under stress condition. The results of this study would be a useful guide for caper producers as well as plant ecophysiological researchers.