Temperature effects on lignin, hemicellulose and cellulose in tropical and temperate grasses

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Abstract
Thirteen tropical and 11 temperate grasses were grown in controlled environment under day/night temperatures of 21/13, 27/19 and 32/24°C. Neutral detergent fibre (NDF) was prepared from the fifth leaf on the main stem of each plant, 2 days after it had reached maximum length. Panicum maximum var. trichoglume (tropical) and Lolium perenne cv. S24 (temperate) were also harvested at 4,8, and 12 days after this stage of development. For the tropical grasses NDF values, corrected for starch and protein, decreased with increasing growth temperature, whereas in the temperate species they increased. In the tropical group the decrease in NDF was due to a lower cellulose content, whereas hemicellulose and lignin levels generally tended to increase slightly with increasing temperature. In the temperate grasses, lignin, hemicellulose and cellulose levels all showed a consistent increase with growth temperature. At each growth temperature the lignin content of the species in the tropical group had a significant negative correlation with in vitro digestibility, and lignin appeared to be more closely associated with hemicellulose than with cellulose. In contrast, at each temperature, variation in digestibility between species of the temperate group was not correlated with lignin. Levels of cell wall components in the later-harvested material from Lolium varied in a similar manner to that of the younger growth stage, whereas older Panicum cell wall constituents showed more variability.