Defoliation frequency and cultivar effects on the storage and utilisation of stolon and root reserves in white clover

The effects of defoliation frequency (2 or 6 defoliations over a 91-day per iod) on the reserve status and growth rate of 2 white clover cultivars, cvv . Irrigation (medium-leafed) and Haifa (large-leafed), were examined over t he final 42 days of the defoliation treatments. The clover plants consisted of single stolons growing in a sand/scoria mix in an unheated glasshouse, and were fertilised weekly with a solution containing essential nutrients e xcluding nitrogen. More frequent defoliation reduced the leaf appearance rate, stolon elongati on rate, and plant size, and increased stolon death, with all of these effe cts being less pronounced in Irrigation than in Haifa (18% v. 30%, 60% v. 8 0%, and 23% v 34%, respectively, for leaf appearance rates, stolon elongati on rates, and the proportion of stolon length that died). With infrequent defoliation, the combined utilisation of starch and water-s oluble carbohydrate (WSC) reserves in the first 14 days after defoliation w as equivalent to 15% of the plant weight at defoliation, and to 95% of the new leaf produced during that period. Frequent defoliation reduced the rese rve content and remobilisation less in Irrigation than in Haifa, with the c ombined mass of remobilised starch and WSC over the first 14 days after def oliation being 2.9% and 2.0% of the plant weight at defoliation, and 29% an d 19% of leaf production over that period, for Irrigation and Haifa, respec tively. The greater reserve mobilisation in Irrigation than in Haifa plants under f requent defoliation probably contributed to their higher growth rates and r educed stolon death. These cultivar differences with frequent defoliation s uggest that Irrigation is more suited to frequent defoliation than Haifa.