Abstract
Problem statement: Approximately 20% of sugarcane (Saccharum spp.) is grown on sand soils in south Florida, USA. Sugarcane yields in the region linearly increased in last 33 years on organic (muck) soils, but not on sand soils. Water deficit during the formative growth phase on sand soils probably limits sugarcane yields. Approach: A greenhouse study was conducted in 2009 and 2010 to evaluate the physiological and growth responses of sugarcane to water-deficit stress during formative growth. Treatments included organic (muck) and sand soils and two water regimes Well Watered (WW) and Water-Deficit Stress (WS). Sugarcane cultivar CP 80-1743 was planted in pots and fertilized with N, P and K based on soil analyses. All pots were well watered until 58 days after planting, when water was withheld from the WS pots. During the WS treatment, plant growth rate, leaf Relative Water Content (RWC), proline content and photosynthesis components were measured. Final tillers, Green Leaf Area (GLA) and shoot biomass were determined 27 (in 2009) or 22 (in 2010) days after initiating the WS treatment. Results: Stress symptoms of sugarcane plants appeared 7-10 days earlier on sand soil than on muck soil. Water stress reduced stomatal conductance (gs), Photosystem II Photochemical Efficiency (ΦPSII), leaf Photosynthesis rate (Pn), the number of tillers and GLA, resulting in reduced shoot biomass, especially on sand soil. Neither leaf RWC nor proline content was a sensitive WS indicator. Conclusion: Nondestructive measurements of physiological traits of gs, ΦPSII and Pn during the formative stage may be useful for early detection of water stress in sugarcane.
Highlights
Sugarcane is an important crop in Florida, USA with a total of 157,074 ha in 2008 (Rice et al, 2009)
Scientists in Florida are conducting a comprehensive review of the Canal Point (CP) program to identify breeding and management strategies that will improve sugarcane yields for sand soils without compromising the progress being made for muck soils (Glaz and Kang, 2008)
Our results indicated that changes in ΦPSII during development of water stress (Fig. 2e) were similar to changes in leaf Photosynthesis rate (Pn) (Fig. 2a), indicating that ΦPSII is a useful physiological trait for early detection of sugarcane water stress
Summary
Sugarcane (a complex hybrid of Saccharum spp.) is an important crop in Florida, USA with a total of 157,074 ha in 2008 (Rice et al, 2009). It is well known that water-deficit stress alters a variety of physiological processes such as stomatal conductance, transpiration rate, leaf temperature, photochemical electron transport, photosynthesis, respiration and photo-assimilate partitioning (Gardner et al, 1984) These physiological traits are directly or indirectly associated with crop growth and yields (Tollenaar and Aguilera, 1992; Zhang et al, 2001; Silva et al, 2007). Based on the low yields and lack of genetic gain on sand soils (Edme et al, 2005), we hypothesized that physiological processes are negatively affected by abiotic stresses, especially water-deficit stress during sugarcane formative growth on the Florida sand soils. Identification of physiological and growth responses in sugarcane to water-deficit stress should aid to better understand physiological mechanisms and improve cultivar selection and field management for sand soils in Florida. The specific objectives were to: (i) determine leaf Relative Water Content (RWC), proline content, photosynthesis components, plant growth and dry matter production and (ii) identify growth and physiological traits that can be used to effectively evaluate status of water stress in sugarcane
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