Abstract: The green organs in wheat (Triticum aestivum L.) consist of leaf and non-leaf organs including ear, culm, and sheath. Understanding the structures and functions of these non-leaf green organs under abiotic stresses will help to explore the potential of photosynthesis of the whole plant. In order to identify the photosynthetic adaptation of different green organs to drought stress in winter wheat, the changes of chloroplast ultra-microstructure and function of the organ above were studied in a field experiment in the 2002–2003 growth season (a medium rain fall growth season) using cultivar Shijiajuang 8 with water treatments of no irri-gation (control), irrigating twice at jointing and anthesis stages, and irrigating 4 times at pseudostem erecting, booting, anthesis, and grain-filling stages. Each irrigation received 750 m³ ha^-1 water. Chloroplast ultramicrostructure of flag leaf blade and non-leaf organs (peduncle, flag leaf sheath, glume, and lemma) in response to different irrigation treatments were observed during late grain-filling period, and the net photosynthetic rate (Pn) and Fv/Fm values of different green organs were measured simultaneously. The results showed that the chloroplast number of non-leaf organs was less than that of leaf blade, and many starch grains were found in the chloroplasts of glume and lemma under sufficient water supplies (irrigating 4 times). Obvious senescence characteris-tics and differences in chloroplast ultramicrostructure were found in different organs of control, and the senescence was signifi-cantly severer in flag leaf than in non-leaf green organs. The chloroplast structure of flag leaf blade and lemma was destroyed under drought stress, while that of peduncle, sheath, and glume showed relatively stable in the late developmental stage under different irrigation regimes. Post-anthesis drought stress decreased P_n and F_v/F_m values in different green organs, but much less affected them in non-leaf organs (peduncle, sheath, and ear). The results indicated greater stability of chloroplast structure and photosynthetic activity in non-leaf green organs at the late grain-filling stage under water stress.

Key words: Wheat, Chloroplast structure, Non-leaf organ, Water stress