Gender-specific seasonal pattern and altitudinal variation in freeze tolerance responses of Seabuckthorn (Hippophae rhamnoides L.)

BACKGROUND: In dioecious species the morphological and physiological adjustment to cold and freezing conditions may differ significantly between male and female individuals due to greater reproductive effort by females. OBJECTIVES: To assess the importance of gender-specific responses of H. rhamnoides of cold acclimation and freeze tolerance in trans-Himalayan environments. METHOD: We measured the proline contents in leaves and shoots in male and female H. rhamnoides from mid August to mid December in standing crop. RESULTS: Proline content in leaves showed a significant increasing trend from August to October followed by a steady decline from November onwards in both the genders. Progression in season from August to December is related linearly to the increase in proline contents in both male (R-2 = 0.967) and female (R-2 = 0.926) shoots. Increase in altitude (3202-3812m amsl) of plant origin is related linearly to increase in proline contents in both male (R-2 = 0.676) and female (R-2 = 0.858) shoots. The overall proline contents in both leaves and shoots were significantly higher in male (112 +/- 77, 143 +/- 66 mu Mg-1, respectively) than in female (87 +/- 46, 119 +/- 82 mu Mg-1, respectively). CONCLUSION: The study suggested sexually dissimilar responses to cold and freezing conditions in H. rhamnoides and that male possess a better self protection mechanism than female. Leaves developed tolerance against cold stress more quickly than shoots.