Photosynthesis of White Clover (Trifolium Repens L.) Germplasms with Contrasting Leaf Size
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In a growth chamber experiment, we determined net photosynthetic rate (P(N)) and leaf developmental characteristics of cultivars of a relatively small-, intermediate-, and a large-leaf genotype grown under irradiance of 450-500 mol(photon) m-2 s-1 (HI), shade [140-160 mol(photon) m-2 s-1] (LI), and after a shade-to-irradiation (LI HI) transfer. Differences in physiological responses of the genotypes were more pronounced in HI and LIHI plants than in LI plants. The small- and intermediate-leaf sizes had greater P(N) in the first measured leaf than the large-leaf type by 70 and 63% in HI plants, and by 23 and 18% in LIHI plants, respectively. Similar relationships were observed in the next developed leaf. The LI plants did not differ significantly in P(N). Greater P(N) in the small- and intermediate-leaf size genotypes were not associated with greater total dry matter of the plant. Under irradiation, the large-leaf genotype accumulated more total nonstructural saccharides (TNS) and starch than the small- or intermediate-leaf size plants. TNS and starch concentrations in LI plants were about one-half those of HI and LIHI plants. These results should help to develop management practices that capitalize upon the competitive features of white clover in mixed-species swards.
