Morphological and physiological responses of two varieties of a highland species (Chenopodium quinoa Willd.) growing under near-ambient and strongly reduced solar UV-B in a lowland location.

Morphological and physiological responses of seedlings to different solar UV–B irradiances were evaluated in two varieties of quinoa (Chenopodium quinoa Willd.), a crop species from Andean region of South America. Cristalina and Chucapaca varieties were grown at 1965m a.s.l in a glasshouse under natural light conditions for 18days, and then transferred to outdoors under near-ambient (+UV–B) and strongly reduced (−UV–B) solar UV–B radiation. Exposition to −UV–B increased cotyledon area and seedling height in Cristalina variety whereas leaf number decreased compared to +UV–B. By contrast Chucapaca variety was not affected by UV–B treatments. Seedling fresh weight (FW), root length and leaf thickness did not show significant differences between +UV–B and −UV–B treatments. Mesophyll tissue was slightly affected by solar UV–B reduction. Chlorophyll content was differentially affected by UV–B treatments. Under +UV–B the highest value was observed in Cristalina variety, while in Chucapaca it was observed under −UV–B treatment. Chlorophyll content was slightly higher in leaves than in cotyledons, but there was no difference in the distribution pattern. Chlorophyll a/b ratio and carotenoid content did not show significant differences between UV–B treatments. Leaf UVB-absorbing compounds showed significant differences between UV–B treatments in Chucapaca only, while there were no significant differences in Cristalina variety. UVB-absorbing compounds of cotyledons did not show significant differences between +UV–B and −UV–B treatments. Sucrose, glucose and fructose showed different distribution patterns in cotyledons and leaves of the two varieties under near-ambient and strongly reduced UV–B. Results demonstrated that varieties of quinoa exhibit different morphological and physiological responses to changes in solar UV–B irradiance, but these responses cannot be used to predict the sensitivity to solar UV–B during a short-term exposition. Also, this study can be useful to learn about the plasticity of metabolic pathways involved in plant’s tolerance to solar UV–B radiation.