Sugarcane Leaf Photosynthesis and Growth Characters during Development of Water-Deficit Stress

Yield and profitability of sugarcane (a complex hybrid of Saccharum spp.) grown on sand soils are much lower than on organic soils in Florida owing to biotic and abiotic stresses. A greenhouse study was conducted using a sand soil to identify effects of water deficit stress (WS) during sugarcane early growth on leaf photosynthetic components, plant growth, and dry matter accumulation. Treatments included two sugarcane genotypes (CP 01-2390 and CP 80-1743) and two water regimes (well watered [WW] and WS). All plants were well watered before initiating WS. Water was withheld from the WS pots when plants reached seven to eight leaves on the primary stem. During the WS treatment, plant growth and leaf photosynthetic components were measured. Final green leaf area (GLA) and shoot biomass were determined at the end of the experiment. Water stress depressed leaf relative chlorophyll level (SPAD), stomatal conductance (g(s)), leaf net photosynthetic rate (Pn), transpiration rate (Tr), transpiration use efficiency (TUE) of photosynthesis, and GLA, resulting in reduced shoot biomass. CP 01-2390 was superior to CP 80-1743 in most measured physiological and growth traits under the WW and WS conditions, suggesting that selection of genotypes with tolerance to WS while improving irrigation management will improve sugarcane yields on sand soils. Physiological and growth traits, such as SPAD, g s, Pn, Tr, TUE, GLA, tillering, and stalk length, may be useful for early detection of WS and for evaluation of sugarcane genotypes in the stress tolerance.