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The physiological basis of yield in asparagus ( Asparagus offincinalis L.) is poorly understood, but some reports have inferred a link between lateral fern photosynthesis (A) and annual spear yield. Gas exchange measurements were made on single lateral ferns of mature asparagus plants in the field and younger, potted plants. Among three cultivars with different levels of yield, the light‐saturated rate ofphotusynthesis (A sat ) was positively associated with crop yield in both sets of plants. There was a highly significant correlation between A sat and stomatal conductance (gs). A sat also increased with fern nitrogen, chlorophyll, and soluble protein concentrations across the cultivars. These data imply that differences in both gs and photosynthetic capacity contributed to the variation in A sat , and this was supported by AJCI (internal CO 2 concentration) analysis. Variation in photosynthetic capacity was related to genotypic differences in cladophyli diameter and thus the content (per unit sudace area) of photosynthetic biochemical constituents and, possibly, mesophyll resistance to CO 2 diffusion. The possibility of genotypic variation in other photosynthetic parameters was also noted. It is concluded that fern A sat might be a predictor of yield in asparagus, and of potential use in early selection for breeding, but confirmation of such a relationship requires investigation in a wider range of genotypes.
Faville et al. (Thu,) studied this question.