KAMAL EL-SIDDIG1, GEORG EBERT2, JENS GEBAUER1
1Agricultural Research & Technology Corporation, Cotton Research Program, Sudan
2Humboldt-Universität zu Berlin, Department of Fruit Science, Germany
Tamarind (Tamarindus indica L., Leguminosae) is a tropical multipurpose tree with many uses, ranging from food and beverages to medicinal and industrial purposes (Morton, 1982). The ripe tamarind fruits are consumed fresh, in desserts, or processed into refreshing soft drinks enjoyed during hot summer months in the Sudan. The plant is native to tropical Africa and grows wild throughout the Sudan., but is cultivated on a commercial scale mainly in India, Thailand, the Philippines and Mexico. Tamarind plantations in the Sudan are practically non-existent and wild stands are continuously being overexploited to meet local consumption and export. Unsustainable harvesting methods of wood and fruit, livestock grazing, land clearing and bush fires pose a great threat to natural stands. Risks are further amplified by recurrent episodes of drought, which plagued the country since 1983. Effects of drought are particularly severe on seedlings or new transplants because their roots occupy the uppermost layers of soil where the most rapid drying occurs
Plants have evolved many physiological, morphological and anatomical characteristics to become better adapted to water-scarce environments. A better understanding of the way that drought stress affects plants would help in the development of improved cultivars and better production systems to reduce the effects of drought. This paper described changes biomass production and leaf gas exchange of Tamarindus indica seedlings subjected to repeated cycles of drought in comparison to well-watered seedlings. Results suggest that the growth decrease in WS-plants was related mainly to growth inhibition of aboveground parts and, to lesser degree, to a decrease in root growth. In WS-seedlings, root/shoot ratio was 0.25 compared to 0.21 for the control plants. This may indicate an adjustment in biomass allocations pattern to favour root tissues at the expense of shoot tissues. Greater root biomass will tend to increase the capabilities of water uptake while at the same time lower shoot biomass would be expected to reduce the amount of water loss due to an expected smaller leaf area. It may also reflect greater ability of roots to maintain turgor through osmotic adjustment.
We are grateful to the 'Alexander von Humboldt Foundation' for awarding a Feodor Lynen Research Fellowship to Dr. Jens Gebauer.
Keywords: Biomass production, leaf gas exchange, tamarind, water stress