Temperature effects on anatomy and digestibility of leaf and stem of tropical and temperate forage species.

Abstract

Growth temp. effects on anatomy and digestibility of leaf and stem of tropical and temperate forage species (Cynodon dactylon, Panicum maximum var. trichoglume, P. laxum, Lolium perenne and Medicago sativa), representing a range of anatomical types, was evaluated. Plants were grown in controlled-environment greenhouses at day/night temp. of 32/26 or 22/16 degrees C. Tissues of defined development stage were sampled for analysis of proportion of cell types, cell wall thickness, staining properties and digestion, using transverse sections on microscope slides immersed in rumen fluid. Leaf and stem harvested from whole plant tops was analysed for OM digestibility (OMD), cell wall digestibility (DCW), lignin, cell wall and insoluble ash. Temp. had little consistent effect on the proportion of different cell types, or the thickness of cell walls, cell wall content or insoluble ash. The digestion of the walls of sclerenchyma, bundle sheath and xylem cells was lower in tissues grown at the higher temp., especially for leaf. High temp. decreased OMD by an average of 6.6 percentage units for leaf and 12.4 percentage units for stem in the grasses, and by 2.6 percentage units for both tissues in M. sativa. The decrease in OMD and DCW with high temp. (excluding stem of M. sativa) was correlated with increase in lignin concn. High temp. appeared to increase the intensity of lignification of the existing lignified cells rather than increase the proportion of cells becoming lignified. Staining intensity was an insensitive indicator of this change in lignification. (Abstract retrieved from CAB Abstracts by CABI’s permission)