Varietal Variation in Stomatal Conductance, Transpiration and Photosynthesis of Commercial Sugarcane Varieties Under Two Contrasting Water Regimes

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 (E₁) 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/E₁) 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, E₁ 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/E₁, and lower g_s, E₁, 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