Effect of High Temperature in Pollen Morphology and Plant Growth in Quinoa.

Quinoa has gained considerable attention worldwide due to its nutritional and health benefits, most notably as a gluten-free, high protein crop with a well-balanced complement of amino acids. High temperature has been reported as a serious obstacle to global expansion of this crop. The gametophyte development is the most critical stage for different crops in high temperature conditions. The objective of this study was to evaluate the plant growth and pollen morphology in quinoa after exposure to high temperature. Pollen morphology was analyzed with transmission electron microscopy and scanning electron microscopy in two different genotypes of quinoa, subjected to 22^○C/ 16^○C (day/night) as control conditions and 40^○C/ 24^○C as heat conditions in growth chamber experiments. Moreover, pollen viability, pollen germination, yield per plant, plant height, leaf greenness and rate photosynthesis were measured on both conditions. Our results show that heat stress reduced the pollen germination and viability. Although no morphological differences were observed in the pollen surface, both the pollen wall (intine and extine) thickness and the germ pore increased due to heat stress. Plant height, yield per plant and leaf greenness were not affected by high temperature. On the other hand, the primary branches of the panic inflorescent were extended due to heat stress. Finally, high temperature improved the rate of photosynthesis (A_net) as a function of the photosynthesis photon flux densities. In conclusion, our results show that high temperature affects the viability and wall structure of quinoa pollen, but not the plant growth. However, evaluation of plant growth and quinoa pollen in field conditions is necessary, where quinoa plants are exposed to combination of high temperatures, drought, and dry winds.