Abstract
The study was conducted to evaluate some physiological characters of commercial sugarcane varieties under different growing conditions in Sri Lanka. A field experiment was conducted at the Sugarcane Research Institute, Uda Walawe (6°21'N latitude, 80°48'E longitude and 76 m altitude) using eight sugarcane ( Saccharum hybrid L.) varieties grown under irrigated and rainfed conditions in a split plot de-sign. Stomatal conductance ( g s ), instantaneous transpiration rate ( E 1 ) and photosynthetic rate per unit leaf area ( P n ) were measured. Canopy stomatal conductance ( g c ), instantaneous canopy transpiration rate ( E c ) and transpiration efficiency ( P n / E 1 ) was calculated. The behaviour of g s in many respects to the moisture availability and growing stage was similar to the responses seen in P n . Water deficit significantly reduced g s , E 1 and P n . Recovery of g s and P n from water stress with rainfall was quite rapid under rainfed conditions. The varieties Co775, SL8306, SL7103 and SL88116 which had higher P n and P n / E 1 , and lower g s , E 1 , g c and E c showed comparatively superior physiological performances under rainfed conditions. Water conservation through lowering stomatal conductance, both at the individual leaf and canopy level, and higher photosynthetic rate were identified as some physiological mechanisms responsible for drought tolerance of sugarcane. Key words: Sugarcane; Stomatal conductance; Transpiration; Photosynthesis; Water regimes DOI: 10.4038/tare.v12i2.2798 Tropical Agricultural Research & Extension 12(2): 2009 pp.97-102
Highlights
Sugarcane is one of the extreme types C4 plant and it can have extraordinarily high rates of per unit leaf area (Pn), found in crop plants (Irvine 1967; 1975 and 1983)
Ber 2002, which fell within the period when the crops were experiencing a prolonged and continuous soil moisture depletion, showed the significant varietal variation of gs and El within and between water regimes (Table 1)
Among the eight varieties tested, there was no single variety in which all above characters performed at favourable levels under different conditions
Summary
Sugarcane is one of the extreme types C4 plant and it can have extraordinarily high rates of Pn, found in crop plants (Irvine 1967; 1975 and 1983). Sugarcane could maintain a higher rate of Pn under full sunlight with lower rates of canopy transpiration rate (Ec) to increase the water use efficiency (De Costa 2000). The light saturated maximum Pn in commercial varieties of sugarcane ranges from 31 to 53μmol CO2m-2s-1 (Irvine 1967 and Roberts et al 1990). It is at a maximum during the grand growth stage and tends to decrease during late grand growth and maturation phases of sugarcane (Gascho and Shih 1983)
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