Morphological Responses of Sugarcane to Long-Term Flooding

Sugarcane (Saccharum spp.) in south Florida is often subjected to flooding due to intense summer rainfall or tropical storms. While there has been considerable research on the response of sugarcane cultivars to high water tables, there is a lack of information on cultivar morphological adaptation to long-term flooding. An experiment was established in Belle Glade, FL to examine: (i) effects of a July– September flood on the morphological characters of cv. CP 80-1743 and CP 72-2086 and (ii) significant flood 3 cultivar interactions that could be used to screen sugarcane germplasm. Sugarcane leaf, stem, primary root, adventitious root, and aerenchyma development were measured in the plant cane (2003) and second ratoon crops (2005). Morphological changes in response to flooding were similar in both years, with flooding leading to a 38% reduction in leaf weight, 4 to 15 times greater adventitious root development, 108% greater aerenchyma pipe extension, and 115% greater aerenchyma pipe diameter. Both cultivars responded to flooding by producing aboveground adventitious roots at the expense of belowground primary root biomass. A significant cultivar 3 flood interaction on aerenchyma extension and diameter was noted. Under nonflooded conditions, CP 722086 produced constitutive aerenchyma more than halfway up the stalk, whereas CP 80-1743 produced aerenchyma only 10% up the stalk. Aerenchyma development up the stalk may be a useful screening tool to identify flood-tolerance in sugarcane cultivars. SUGARCANE is an important economic crop in the tropics and subtropics due to its high sucrose content and increasing interest in its bioenergy potential. In Brazil in 2004, 14.4 billion L of ethanol were produced from sugarcane (Pessoa et al., 2005). Sugarcane in south Florida is often exposed to flooding during the summer months. Floods, particularly if prolonged, have the ability to negatively affect sugarcane yields (Berning et al., 2000). There is evidence, however, of tolerance to flooding in Florida Canal Point (CP) sugarcane germplasm. Sartoris and Belcher (1949) reported that CP sugarcane clones survived a 105-d flood following two tropical storms in 1947. Differences in “nodal” (adventitious) root development were recorded among genotypes. Deren et al. (1991b) screened 160 CP clones for flood tolerance during a 5-mo flood (July–November) Several clones, including commercial cv. CP 72-2086, recorded sucrose yield reductions ,30% in flooded compared to nonflooded conditions. The authors surmised that CP germplasm was inadvertently selected for flood tolerance due to tropical storms in the history of the breeding program, and concluded flood tolerance was present in modern CP clones. Glaz et al. (2002) recorded variability among commercial CP cultivars in tolerance to high water tables, and recommended screening of genotypes under high water tables. CP 72-2086 was not affected while CP 80-1743 yields were reduced 25% in the high water table treatment. Glaz and Gilbert (2006) found that 2-d periodic floods increased cane and sucrose yields in plant cane crops of CP 72-2086 and CP 80-1827, and Chabot et al. (2002) reported that sugarcane transpiration rates were maintained under high water tables in cv. CP 66-345. Glaz et al. (2004b) reported that periodic flooding and draining to water table depths of 16 to 50 cm did not affect sugarcane leaf photosynthesis. Two common morphological changes of sugarcane in response to flood are the development of porous aerenchyma tissue (“piping”) in the stalks and roots, and adventitious root development. Glaz et al. (2004a) measured aerenchyma development in CP sugarcane stalks and found constitutive aerenchyma (aerenchyma developed under nonflooded conditions) in CP 95-1429, which maintained yields over the growing season, despite repeated 7-d floods and extensive drainage. The authors surmised that constitutive aerenchyma development would be a useful adaptation for flood tolerance. They also found that flooding reduced yields of CP 95-1376, which did not possess constitutive aerenchyma (Glaz et al., 2004b).Van derHeyden et al. (1998) reported that all 40 CP genotypes studied possessed constitutive root aerenchyma. However, there were differences in the extent of aerenchyma development among clones. Development of adventitious roots in response to flooding is thought to be a tolerance mechanism to increase root aeration that allows the plant to maintain root function during flooding (Kovar and Kuchenbuch, 1994). These aboveground roots tend to grow horizontally to remain near the water–air interface. Aerenchyma formation in adventitious roots in response to flooding has been reported in a range of wetland and dryland grass species (McDonald et al., 2002). Srinivasan and Batcha (1962) flooded 68 clones from Saccharum and related genera for 6 mo. Profuse adventitious root and aerenchyma development in tolerant clones was noted. Webster and Eavis (1972) noted a reduction in sugarcane leaf area during a 30-d flood. Additionally, sugarcane root systems developed a dense mat of aerotropic, small diameter roots when flooded. The authors theorized reduction in root diameter under R.A. Gilbert and C.R. Rainbolt, Univ. of Florida, EREC, 3200 E. Palm Beach Rd., Belle Glade, FL, 33430; D.R. Morris, USDA-ARS, Sugarcane Field Station, 12990 U.S. Hwy. 441, Canal Point, FL 33438; and A.C. Bennett, USDA-NRCS, 1120 S. Main St., Frederick, OK, 73542. Names of the products are included for the benefit of the reader and do not imply endorsement or preferential treatment by the University of Florida or USDA. Received 5 Mar. 2007. *Corresponding author ([email protected]). Published in Agron. J. 99:1622–1628 (2007). Sugarcane doi:10.2134/agronj2007.0085 a American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: CP, Canal Point; EAA, Everglades Agricultural Area; EREC, Everglades Research and Education Center. R e p ro d u c e d fr o m A g ro n o m y J o u rn a l. P u b lis h e d b y A m e ri c a n S o c ie ty o f A g ro n o m y . A ll c o p y ri g h ts re s e rv e d .