Effect of Light and Water Deficiency on Growth and Concentration of Various Primary and Secondary Metabolites of Aloe vera L.

The effects of abiotic stresses on medicinal plants metabolism are well known, but how plants respond to the interaction of these stressors is little understood. Therefore, the current experiment was aimed to investigate changes in growth and concentration of various primary and secondary metabolites of A. vera grown under water deficit and different light intensity conditions. A split-plot in time research was laid out in a randomized complete block design with four replications in a research greenhouse. The factorial combination of four irrigation regimes (irrigation after depleting 20%, 40%, 60%, and 80% of soil water content) and three light intensities (50%, 75%, and 100% of sunlight) were considered as the main factors. Sampling time was considered as sub factor. The results showed that the highest leaf, gel, and peel fresh weights were observed when the plants were subjected to low light intensity and irrigation was done after depleting 20% soil water moisture. Plants developed under full sunlight produced more pups (4.30, 3, and 3.75 per plant, 90, 180, and 270 days, respectively) and leaves (14.25, 18, and 21.25 per plant, 90, 180 and 270 days, respectively) and showed the higher fresh (165.75 g per plant) and dry root (37.60 g per plant) weight. These traits decreased with increasing water deficit severity during all the sampling times. Glucose (79.30 mg g DW− 1, 270 days), fructose (233.50 mg g DW− 1, 270 days), aloin (27.68%, 90 days), proline (2.07 mg [g FW]-1, 90 days) and phosphoenolpyruvate carboxylase (PEP-Case) (0.463 mmol NADH/g prot*min, 90 days) increased with increasing light intensity and water deficit severity during all the sampling times. Although high light intensity and water deficit led to yield and growth reduction, concentration of various primary and secondary metabolites increased. The results suggest that reduction in light intensity mitigates adverse effects of water deficit by inducing primary and secondary metabolites changes. It can be considered as an acclimation mechanism under water deficit conditions to avoid yield loss in A. vera production.