RICE SCIENCE ›› 2009, Vol. 16 ›› Issue (1): 65-71 .DOI: 10.1016/S1672-6308(08)60058-X

• Research Paper • Previous Articles     Next Articles

Effects of High Temperature Stress on Microscopic and Ultrastructural Characteristics of Mesophyll Cells in Flag Leaves of Rice

ZHANG Gui-lian; CHEN Li-yun; ZHANG Shun-tang; ZHENG Hua; LIU Guo-hua   

  1. Rice Research Institute, Hunan Agricultural University, Changsha 410128, China
  • Received:2008-07-09 Online:2009-03-28 Published:2009-03-28
  • Contact: CHEN Li-yun
  • Supported by:
    the National Natural Science Foundation of China (Grant No. 30500315); the Agricultural Technological Results Transformation Item of Ministry of Agriculture, China (Grant No. 05EFN214300193) and the Educational Foundation of Hunan Province, China (Grant No. 07C360).

Abstract: The microscopic and ultrastructural characteristics of mesophyll cells in flag leaves of two rice lines (a thermo- sensitive line 4628 and a thermo-resistant line 996) under high temperature stress (37°C during 8:00–17:00 and 30°C during 17:00–8:00) were investigated using an optical and a transmission electron microscopy. The membrane permeability and malondialdehyde content increased under the high temperature stress, and the increase of both variables was greater in the line 4628 than in the line 996. Under the high temperature stress, the line 996 showed tightly arranged mesophyll cells in flag leaves, fully developed vascular bundles and some closed stomata, whereas the line 4628 suffered from injury because of undeveloped vascular bundles, loosely arranged mesophyll cells and opened stomata. The mesophyll cells in flag leaves of the line 4628 were severely damaged under the high temperature stress, i.e. the chloroplast envelope became blurred, the grana thylakoid layer was arranged loosely and irregularly, the stroma layer disappeared, many osmiophilic granules appeared within the chloroplast, the outer membrane of mitochondria and the nucleus disintegrated and became blurred, the nucleolus disappeared, and much fibrillar-granular materials appeared within the nucleus. In contrast, the mesophyll cells in flag leaves of the line 996 maintained an intact ultrastructure under the high temperature stress. From these results, it is suggested that the ultrastructural modification of the cell membrane system is the primary plant response to high temperature stress and can be used as an index to evaluate the crop heat tolerance.

Key words: rice, high temperature stress, heat tolerance, flag leaf, microscopic characteristic, ultrastructure characteristic, mesophyll cell, cytology