Quantification of leaf wax and cutin monomer composition in Pima (Gossypium barbadense L.) and upland (G. hirsutum L.) cotton

Climatological drought is a historic problem that limits agricultural production worldwide. Reducing transpirational water loss can conserve soil moisture and confer drought tolerance to crops by delaying their dehydration during periods of drought stress. Transpiration can be regulated by the hydrophobic plant cuticle, which coats the aerial surfaces of plants and limits water loss through non-stomatal transpiration. The cuticle is composed primarily of two lipid classes, free cuticular wax components and the polymerized cutin polyester. Many studies suggest that both waxes and cutin are important in maintaining plant water status during periods of drought. Five varieties of Pima cotton (Gossypium barbadense) and six varieties of upland cotton (G. hirsutum) were examined for variation in leaf wax and cutin composition. Wax and cutin monomers were analyzed using an Agilent 7890A gas chromatograph and a 5975C mass spectrometer (GC–MS). Results show that upland cotton produces more total wax than Pima varieties, whereas Pima cotton produces more total cutin than upland varieties. In both species, alcohols were the most abundant wax compounds and dihydroxy monobasic acids were the most abundant cutin monomers.