Evaluation of genotypic variation during leaf development in four Cucumis genotypes and their response to high light conditions

Abstract Physiological responses to differences in light intensity were studied in four genotypes of Cucumis with differences in leaf greenness. The four genotypes were C. ×hytivus (synthesized allotetraploid, yellow-green); its parents, C. hystrix (wild Cucumis species, dark green) and BeijingJietou (cultivated cucumber, green); and M1 (a chlorophyll deficient mutant of cultivated cucumber, yellow-green). The plants were subjected to a photosynthetic photon flux density (PPFD) of either 800 μmol m −2  s −1 or 200 μmol m −2  s −1 in climate chambers for 20 days. Plant growth, chlorophyll (Chl) content, gas exchange, Chl fluorescence parameters and carbohydrate partitioning in the four genotypes were studied. The four genotypes showed different amounts of Chl accumulation and the genotypic differences led to divergent photosynthetic capabilities, carbohydrate partitioning and photosynthetic responses to high light. The original natural habitat characteristics of the two species may also play an important role in the divergence. Moreover, the ability of the yellow-green M1 to slowly increase the leaf Chl content during leaf development was aligned with a long leaf life span, maintaining high levels of photosynthesis, which was not the case in the yellow-green C.  × hytivus . In addition, F v / F m is such a sensitive parameter that it should not be evaluated alone for high light stress without the context of the prevailing growth light environment.