Responses of two main Andean crops, quinoa (Chenopodium quinoa Willd) and papa amarga (Solanum juzepczukii Buk.) to drought on the Bolivian Altiplano: significance of local adaptation.

摘要

In field trials in 1991/92 at Patacamaya on the Bolivian altiplano (alt. ?000 m) with quinoa cv. Sajama and Sisa and bitter potatoes cv. Luki, studies were made of the effects of drought on leaf water potential, stomatal conductance (gs), transpiration rate (Tr), photosynthesis rate (Pn) and yield. The crops suffered severe water deficit, especially during the last two months of the crop cycle. Rainfall was 62 mm and the potential evapotranspiration was 186 mm. Drought caused massive drops in leafwater potential, gs, Tr and Pn in all crops. There was a major, rapid stomatal closure with an associated two-thirds reduction in Tr and Pn and a great decrease in pre-dawn and minimum leaf water potentials in quinoa at the beginning of the drought period. As drought continued, gs, Tr and Pn remained relatively stable while minimum leaf water potential reached values below -4 MPa. Quinoa offset stomatal closure by improved and maintained high leaf water use efficiency (Pn/Tr = 2). The high dry matter yield (around 2500 kg ha-1) indicates the efficiency of these responses. Bitter potatoes showed stomatal tolerance to water deficit and a stable gas exchange during the first four weeks of drought, but gs, Tr and Pn decreased greatly thereafter and Pn/Trremained relatively low (0.8) compared with quinoa during the whole experiment. Dry matter yield was lower than quinoa but remained relatively high (1920 kg ha-1) under the drought conditions. Pre-dawn leaf water potential of quinoa and bitter potatoes was closely correlated with gas exchange rates.