The influence of water stress (drought) on the mineral and vitamin potential of the leaves of Ocimum gratissimum (L).

Abstract

The influence of water stress (drought) on the mineral and vitamin potential of the leaves of Ocimum gratissimum was investigated. Cultivated O. gratissimum plants grown in plastic planting buckets were subjected to mild water stress by irrigating each planting bucket with 500 ml of water once in a week. On the other hand, in the control treatment, each planting bucket was irrigated with 750 ml of water three times in a week. Treatment commenced two months after seed emergence. The leaves of the plants were harvested one month later for analysis. Results obtained indicated that water stress (drought), significantly (p <0.05) reduced the percentage potassium and calcium content of the leaves of O. gratissimum. Conversely, water stress led to significant increase (p<0.05) in the percentage concentration of nitrogen in the plant’s leaves. Water stress also was found not to have any significant effect in the sodium, magnesium and phosphorous content of the leaves of the plants. The ascorbic acid content of the leaves of O. gratissimum was significantly ( p<0.05) decreased by water stress. Water stress had no significant effect on the riboflavin, niacin and thiamine content of the leaves of the plants. The reduction in the potassium and calcium content of the leaves of O. gratissimum might be due to the mobilization of these mineral elements from the leaves to the roots of stressed plants to serve as osmo- protectants, helping the plants to with stand drought. The increase in nitrogen content as a result of water stress might be related to the mobilization of nitrogen to the leaves for the synthesis of specialized amino acids and proteins to enable the plants to resist the effect of drought. Water stressed plants are known to contain higher amount of protein when compared with unstressed plants. The reduction in the concentration of ascorbic acid in water stressed plants might be due to its breakdown in response to drought. The results obtained were discussed in the light of current literatures.