Abstract
The response of some selected physiological and biochemical parameters of tea ( Camellia sinensis L.) plants to moisture stress was evaluated using field grown, mature plants, in Field Gene Bank at Passara, Sri Lanka, to identify traits that are associated with drought tolerance which could be used for cultivar screening programs. This study was carried out from July - October 2008. Known contrasting cultivars in terms of drought tolerance were selected from the existing gene bank for the measurements. Physiological and biochemical parameters were measured to study the response of tea plants to drought stress. Identification of traits was done by using cluster analysis, cultivar × environment interaction and drought susceptibility index. Reduction of leaf water potential up to -0.75 to -1.5 MPa at the end of the dry period indicated that the plants were exposed to a sufficient level of moisture stress. The drought tolerant cultivars maintained a high water status with substantial rate of photosynthesis as a result of osmotic adjustments, elevated total soluble sugars and also according to previous research, due to deep rooting. Drought susceptible cultivars maintained a lower water status with lower osmotic adjustment. With cluster analysis using rates of photosynthesis and transpiration, relative water content, stomatal conductance and leaf total soluble sugar content, the cultivars could be clearly grouped as tolerant and susceptible cultivars, which agreed with their tolerance level. The parameters which could be successfully incorporated into a drought screening procedure were rate of photosynthesis, stomatal conductance, transpiration rate, relative water content and total soluble sugar content. Key words: Cultivar differences; Drought; Physiological and biochemical responses; Tea ( Camellia sinensis L.). DOI: 10.4038/tar.v22i1.2671 Tropical Agricultural Research Vol. 22 (1): 66-75 (2010)
Highlights
Tea (Camellia sinensis L.), a small, evergreen, woody perennial tree is one of the most important beverage crops in the world
Changes in the measured physiological and biochemical parameters over time as the drought proceeded were studied during July- October 2008
The mean soil moisture content averaged across all varieties was 12.72, 11.29, 9.36, 8.33 and 7.79% (v/v) on daily 1, 2, 3, 4 and 5, respectively (Table 1)
Summary
Tea (Camellia sinensis L.), a small, evergreen, woody perennial tree is one of the most important beverage crops in the world. Tea is grown primarily as a rain fed plantation crop and tea yield is greatly influenced by weather. Monsoonal rains bring sufficient amount of rainfall, irregular distribution within a year causes moisture stress on tea plants mainly during the months of January, March and August resulting in a Drought tolerant ability of tea considerable loss of crop and increased casualties (Karunarathne et al, 1999). Drought is one of the major constraints to improve tea productivity in certain parts of Sri Lanka. Drought stress brings about many physiological, biochemical and morphological changes in plants. Proline and abssesic acid (ABA) accumulate in higher concentrations in many tolerant species in response to water stress, which leads to maintenance of turgour potential in plants (Morgan, 1984). Water stress increases biomass partitioning to roots resulting in increased root dry weights, root length density and root: shoot ratio (De Costa, 2004)
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