Abstract:

Stomata are the channel of CO₂ and water vapour exchange between the plant and atmosphere, and contributing to photosynthesis, transpiration and temperature fitness of plant. There have been many reports about the stomatal structure and characteristics focused on the leaf blades, the major photosynthetic organs, in wheat but only a few reports about stomatal distribution on the ear（especially on the awn）, whereas, no any report on stomatal structure characteristics and their relations to photosynthetic rate and transpiration rate of various non-leaf green organs in wheat under different water condition. In current study, a field experiment was conducted with two cultivars (Lumai 21 and SJZ 8) and three irrigation treatments[No irrigation, Two irrigations (1 500 m³∙hm^-2) and Four irrigations (3 000 m³∙hm^-2) in the growing period of wheat], in order to asses differences in stomatal structure characteristics and their response to irrigation between flag leaf blade and non-leaf green organs (flag leaf sheath, peduncle, glume, lemma, palea and awn). Stomatal structure and distribution on leaf blade and non-leaf green organs in winter wheat were observed, and the stomatal conductance, transpiration rate and photosynthetic rate were also measured in response to different supplemental irrigation treatments. It was showed that under different irrigation treatments, stomata could be found on all surfaces of flag leaf blade , sheath and peduncle, and also on the surface of awn and abaxial surface of glume in ear. However, for lemma, stomata appeared only on the adaxial (not on the abaxial )side under both two and four irrigation treatments, and only on the abaxial side under water stress(no irrigation). In size, stomat apparatus on the ear（glume, lemma, palea and awn）was smaller than that on other organs. With the decrease of water supply, the width of stomatal aperture was also decreased, while both stomat frequency and stomatal aperture length of various organs were increased. Compared with flag leaf blade, non-leaf green organs (flag leaf sheath, peduncle and ear) was less sensitive to supplemental irrigation, and showed higher stability in stomatal conductance, transpiration rate and photosynthetic rate during the later filling period. There was a positive correlation between stomatal conductance and transpiration rate in various organs, while the coefficient of correlation in non-leaf green organs was lower than that in leaf blade. The results suggested that with the decrease of water supply, transpiration rates were declined for both the leaf blades and non-leaf green organs, then, photosynthetic rates might be remarkably decreased in leaf blades, however, relatively stable in non-leaf green organs, which may lead to higher water use efficiency (WUE) in non-leaf green organs than in leaf blades.

Key words: Wheat, Stomatal structure, Non-leaf organs, Photosynthetic rate