Implications of residual leaves in regrowth of tropical forages under shade

C. C. Wong

Abstract

An experiment was conducted at the University of Queensland, Brisbane, Australia during the summer season of 1990/91 to investigate the role of residual stubble leaves for regrowth and persistence of two grasses of contrasting growth habits in shade. The two shade-tolerant grasses, erect Paspalum malacophyllum and stoloniferous P. wettsteinii, were subjected to defoliation at 5 cm and 10 cm cutting heights, with and without removal of residual stubble leaves in two shade levels of 20% and 50% light transmission. Results of the experiment indicated that residual leaves were critical for regrowth of P. wettsteinii after defoliation in dense shade. Removal of residual leaves on stubble resulted in high plant mortality, particularly at the low cutting height brought about by the low and slow tiller production. A resurgence of photosynthetic activity of residual leaves after defoliation implied the importance of residual stubble leaves of P. wettsteinii for regrowth. In contrast, P. malacophyllum was not dependent on its residual leaves for regrowth but on its ability to develop new tiller foliage readily to compensate for the residual leaves removed and to intercept the transmitted light early. Growth habit per se was not the major criterion affecting plant persistence in shade. Morpho-physiological adaptability of forage plants to defoliation through rapid development of tillers and photosynthetic area also contributed to their survival in shade.

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