Proline as an osmolyte modulates changes in morphological and physiological attributes of Capsicum annuum l. under water stress

Abstract Water stress is an inevitable factor which limits growth, development, and production efficiency of vegetables such as Capsicum annuum (Linnaeus) (pepper). This study was carried out to investigate the use of proline as an osmolyte to ameliorate the effect of water stress on morphological and physiological attributes of Capsicum annuum. C. annuum seedlings were subjected to different levels of proline (20, 30 and 40 %) against droughted and well-watered seedlings as control in a completely randomized design. Results showed that water stress limits morphological and physiological attributes of C. annuum, while proline at different levels enhances it. Highest plant height (26.00±0.71 cm) was obtained in C. annuum sprayed with 40% proline. Well-watered seedlings of C. annuum produced the highest numbers of leaves (35.40±4.12 cm) and leaf length (12.60±0.68 cm). In addition, leaf area (89.40±2.04 cm2), specific leaf area (124.24±1.24 m2kg-1) and leaf area index (1.76±1.13 m2m-2) were significantly higher (p < 0.05) in C. annuum seedlings sprayed with 40 % proline compared with other treatments. Relative growth rate (0.30±0.09 mgg-1day-1), net assimilation rate (0.47±0.30 gm-2day-1) and leaf area ratio (0.58±0.11 m2kg-1) as well as, chlorophyll content (9.76±0.02 µgcm2), were higher in C. annuum seedlings sprayed with 40% proline. In conclusion, 20 and 30 % proline sustained morphological and physiological attributes of C. annuum under water stress, but 40% proline produced better ameliorative effects.