Chilling and freezing stress tolerance in Moringa oleifera Lam.

Abstract

Moringa oleifera Lam. is a tree species and popularly known for its multiple uses. The high nutritional value of moringa leaves make it a valuable product for human and animal nutrition. Native of India, moringa grows well in tropical and subtropical areas, being spread worldwide. However, the cold tolerance for this species remains unclear. This study aimed to evaluate the chilling tolerance of moringa under controlled low-temperature regimes and duration and assess whether this species has freeze-tolerance and cold acclimation ability. To evaluate chilling stress, we used three temperature regimes: 20/15, 15/10, and 10/5 °C, of which 10/5 °C was chosen to further investigate the effects of duration and recovery. Morphological (seedling height, number of leaves, number of leaflets, fresh weight, dry weight, and leaf area) and physiological indicators such as a chlorophyll fluorescence parameter (Fv/Fm) and electrolyte leakage (%) were used. All physiological parameters were compromised at progressively cooler temperature regimes. Chilling injury to photosynthetic apparatus and cellular membranes at 10/5 °C for 4 days was completely reversed during the recovery period. In contrast, 8 days of stress caused more severe injury which was only partially recovereable, and 12 days of stress inflicted severest and irreversible injury. The freezing tolerance and cold acclimation ability were evaluated using a laboratory freeze-thaw protocol. The tissues were 50% injured (LT50) at -2.8 °C. In addition, our data indicated the moringa did not show cold acclimation ability after 4 days at 15/10 °C or 4 days at 10/5 °C. The cold tolerance in moringa appears to be a complex system regulated by intensity and duration, and this study provided the baseline information to understand the physiological mechanism involved in these processes.