Water Stress Alters Lignin Content and Related Gene Expression in Two Sugarcane Genotypes

The lignin deposition in the stem of two sugarcane genotypes was assessed on exposure to water stress. The lignin content and the morphoanatomical characterization of the stem indicated that IACSP94-2094 plants are more lignified than those of IACSP95-5000 genotype, under normal water supply conditions, which was especially associated with higher lignin contents in the rind of mature internodes. Water deficit had negative impact on the biomass production, mostly with IACSP94-2094 plants, possibly due to stress severity or higher susceptibility of that genotype during the stem-lengthening phase. Water deficit led to significant alterations in the expression levels of lignin biosynthesis genes and led to an approximate 60% increase of lignin content in the rind of young internodes in both genotypes. It is concluded that the young rind region was more directly affected by water stress and, depending on the genotype, a higher lignin accumulation may occur in the stem, thus implying lower quality biomass for bioethanol production.