DEFOLIATION FREQUENCY AND GENOTYPE EFFECTS ON STOLON AND ROOT RESERVES IN WHITE CLOVER

The effect of defoliation frequency (1 or 3 defoliations over a 42-day period) on the starch, water soluble carbohydrate (WSC), and nitrogen contents of 3 white clover cultivars (Haifa, Irrigation, and S184) wa s examined. The clover plants consisted of single stolons growing in a sand/scoria mix in an unheated glasshouse and fertilised weekly with a nitrogen-free solution. Starch concentrations ranged from 1.3% in fr equently defoliated Haifa to 15.3% in infrequently defoliated S184 pla nts. However, there was no interaction between cultivar and defoliatio n frequency, with the starch concentration in S184 (11.2%) being twice that in Irrigation (6.0%) and 3 times that in Haifa (3.8%). The starc h concentration was also less with frequent (3.7%) than with infrequen t (10.3%) defoliation. The starch was localised in the old stolen mate rial (12.2%), with lower levels of starch in both the young stolen (6. 0%) and roots (4.0%). Furthermore, the cultivar and defoliation freque ncy effects on the starch concentrations were most pronounced in the o ld stolen. More frequent defoliation also resulted in a small reductio n in the WSC and nitrogen concentrations in both the young and old sto lons of Haifa, but not of Irrigation. It was concluded that although s tarch reserves were the principal method of reserve storage in white c lover, WSC and nitrogen reserves will form a relatively large fraction of the reserve pool when starch reserves are depleted under condition s such as frequent defoliation.