Growth and Photosynthesis of Mutant Pea Seedlings

The recessive of gene, producing tendrils in place of leaves,and the recessive st gene, reducing stipule size, produce phenotypesof pea that are termed leafless (afafstst) and semi-leafless(afafStSt). Photosynthesis and growth of these two types werecompared with the conventional phenotype (AfAfStSt) during thefirst 9 days of post-emergent growth. The conventional seedlingshowed faster net photosynthesis per unit dry weight than theleafless phenotype, whilst the semi-leafless seedlings wereintermediate. Differences in dark respiration were small butleafless seedlings had significantly higher rates soon afteremergence. Where the three phenotypes used were isogenic, except for ofand st, the rates of shoot growth were in the same ranking orderas net CO₂ uptake. With three other genotypes, representingthe three phenotypes, more similar shoot growth was found betweenthe conventional and semi-leafless phenotype, possibly becauseof compensating differences in embryonic axis size. The ratesof growth of roots and the rates of dry weight loss from thecotyledons showed no consistent differences between phenotypes. The results are discussed in relation to the potential for thesemi-leafless phenotype as an alternative to the conventionalphenotype for the dried pea crop. Pea seedling, Pisum sativum, leafless pea, photosynthesis, seedling growth