Effect of high temperature on pollen morphology, plant growth and seed yield in quinoa (Chenopodium quinoa Willd.)

Quinoa (Chenopodium quinoa Willd.) has gained considerable attention worldwide during the past decade due to its nutritional and health benefits. However, its susceptibility to high temperatures has been reported as a serious obstacle to its global production. The objective of this study was to evaluate quinoa growth and pollen morphology in response to high temperatures. Pollen morphology and viability, plant growth and seed set, and several physiological parameters were measured at anthesis in two genotypes of quinoa subjected to day/night temperatures of 22/16 degrees C as a control treatment and 40/24 degrees C as the heat stress treatment. Our results showed that heat stress reduced the pollen viability between 30% and 70%. Although no visible morphological differences were observed on the surface of the pollen between the heat-stressed and non-heat-stressed treatments, the pollen wall (intine and extine) thickness increased due to heat stress. High temperature did not affect seed yield, seed size and leaf greenness. On the other hand, high temperature improved the rate of photosynthesis. We found that quinoa has a high plasticity in response to high temperature, though pollen viability and pollen wall structure were affected by high temperatures in anthesis stage. This study is also the first report of quinoa pollen being trinucleate.