Effectiveness of some mechanical, thermal and chemical laboratory treatments on the drying rates of leaves and stem internodes of grass

Abstract

SUMMARYDrying rates of stem internodes of S. 24 perennial ryegrass and S. 37 cocksfoot, some with leaf sheaths and laminae attached, were measured in controlled conditions of air speed, temperature and relative humidity after exposure for 60 sec to dry heat, steam, steam containing petroleum ether vapour, and petroleum ether vapour only. The last treatment was most effective in increasing the drying rate, but a similar effect was obtained by splitting the stem internodes longitudinally or by removing from the larger plant fragments (internodes with leaf) the leaf sheaths and laminae. Observations on leaves with a scanning electron microscope confirmed that the steam and petroleum treatments acted on the surface waxes thus reducing the cuticular resistance to water loss. The presence of internal tissue resistance was demonstrated by anaerobic treatment of ryegrass leaves and stem internodes to disrupt cell protoplasts. The ensuing increase in drying rate was clearest in stems which have a low surface area to volume ratio. The results suggest that the combination of both mechanical damage and thermal or chemical surface treatment could form the basis for more effective methods of increasing the drying rate in the field of crops cut for conservation.