Morphophysiological responses of black pepper to recurrent water deficit

Abstract

This study investigated the effects of recurrent water deficit on drought tolerance traits in black pepper (Piper nigrum L.) 'Bragantina'. Plants were subjected to three cycles of water deficit followed by recovery periods. Water deficit reduced stomatal conductance, photosynthesis, transpiration, and water potential while increasing water-use efficiency. In addition, intercellular CO₂ concentration, leaf temperature, root starch, and adaptive morphological characteristics in leaves and roots increased. Despite these adaptations, plants did not recover vegetative growth after rehydration. The primary tolerance mechanisms observed included increased abaxial epidermis thickness, stomatal density, fine roots, periderm thickness, and starch accumulation in roots. Although gas exchange and leaf water potential were restored, vegetative growth did not fully recover. This study highlights the response of black pepper to recurrent water stress and the underlying mechanisms of its drought tolerance.

Keywords: anatomy; black pepper; drought cycles; gas exchange; vegetative growth.

Fig. 1. Average gas exchange of ‘Bragantina’ subjected to three cycles of water deficit with phases of dehydration and rehydration. (A) Stomatal conductance (g_s); (B) net photosynthetic rate (P_N); (C) transpiration (E); (D) intercellular CO₂ concentration (C_i); (E) leaf temperature (T_LEAF); (F) instantaneous water-use efficiency (WUE); and (G) carboxylation efficiency (CE). Days 9, 27 and 49 represent the final dehydration phase. Days 17 and 36 correspond to the beginning of the dehydration phase of the second and third drought cycle, respectively. The asterisk represents the data collected from the third day of the rehydration phase of the third cycle. The bar corresponds to the standard error of three replications containing the mean of two plants per plot.

Fig. 2. (A) Reducing sugars (RS); (B) total soluble sugars (TSS); and (C) starch contents of ‘Bragantina’ after three cycles of water deficit followed by rehydration (3WD + Recovery) and plants kept irrigated (Control). DM – dry mass. The bar corresponds to the standard error of three replicates consisting of five plants per plot. Means followed by the same letter do not differ statistically from each other according to Tukey's test (p<0.05).

Fig. 3. (A) Height and (B) number of leaves of the ‘Bragantina’ cultivar. (T0) before the imposition of the third water deficit, (3WD + Recovery) plants that suffered three cycles of water deficit and rehydration, and control plants (Control) maintained at field capacity that did not suffer from water stress. The bar corresponds to the standard error of three replications containing the mean of two plants per plot. Means followed by the same letter do not differ statistically from each other according to Tukey's test (p<0.05).