Ultrastructural study of rice tapetum under low-temperature stress

The development of male reproductive organs in rice is very sensitive to various environmental stresses. For example, exposing plants to low temperatures during the heading stage leads to a reduction in grain yield. Here, we grew rice under normal conditions and also at three different temperatures -- 16, 18, and 20 degrees C. Treatment at a low temperature significantly decreased pollen viability and grain production. Cytological observations of the anther showed that the tapetum was the most sensitive to low-temperature stress, resulting in male sterility due to functional loss of the tissue. Detailed observations by transmission electron microscopy suggested that this abnormality was restricted primarily to the ER structures. The endoplasmic reticulum, a highly vulnerable sub-cellular organelle, showed two typical morphological aberrations, one in its pattern of arrangement, the other in the formation of ER bodies. Of our three experimental chilling temperatures, the most severe abnormalities were observed in tapetal cells exposed to 16 degrees C.