关键词: 角质层蜡质, 草原, 围栏封育, 自由放牧

Abstract: Cuticular wax plays an important role in protecting plants from harsh environments. Understanding the responses of cuticular wax to grazing may provide information that can be used to improve grassland management regimes. Leaves from Stipa krylovii, Leymus chinensis and Cleistogenes squarrosa were taken from ungrazed and continuously grazed typical and meadow steppes in Inner Mongolia, China. We analyzed the characteristics of cuticular waxes among plant species and steppe types. The results indicated that the total wax coverage differed greatly among plant species, with the highest in L. chinensis, followed by S. krylovii with the lowest in C. squarrosa. Seven wax compounds were identified in L. chinensis, including fatty acids, alkanes, secondary alcohols, primary alcohols, β-sitsterols, β-diketones and alkylresorcinols. Five wax compounds were identified in S. krylovii including fatty acids, alkanes, primary alcohols, α-amyrin and β-sitsterols and six in C. squarrosa including fatty acids, alkanes, aldehydes, primary alcohols, alkyl esters and β-amyrin. The relative content of secondary alcohols was the highest in L. chinensis while primary alcohols were highest in C. squarrosa, whereas alkanes were highest in S. krylovii. Steppe types significantly influenced total wax coverage and the relative abundance of alkyl esters in C. squarrosa, total wax coverage in S. krylovii, and the relative abundance of secondary alcohols and β-diketones in L. chinensis. Grazing significantly influenced the relative abundance of fatty acids in C. squarrosa, total wax coverage and the relative abundance of α-amyrin and β-sitsterols in S. krylovii, and total wax coverage and the relative abundance of secondary alcohols in L. chinensis. The distribution of different chain length alkanes were relative stable, whereas those of primary alcohols, fatty acids and aldehydes varied greatly between steppe types and grazing management. It is suggested that different steppe plant species developed their own specific cuticular wax adaptive mechanisms during their evolution. Steppe plants may be able to adapt to changing environments through altering wax biosynthesis and deposition.

Key words: cuticular wax, steppe, grazing exclusion, continuous grazing