Yearly Diff erence in Normalized Seed Weight of Cultivated Iris dichotoma Pall. in Mongolia

Maximum of mean seed weight was observed at 1997 while normalised seed weight was significantly higher at 1982 and 1995, compared with other years. Seed weight variation is positively correlated with mean seed weight for earlier rainy season years, excluding later rainy season years (1982 and 1995). Low and high seed weight variation associated for years with colder and wetter in May and with hotter and drier in May, suggesting drought in May might be effective on seed weight variation of I. dichotoma. Moderate normalised seed weight associated for years with hotter in June while high and low normalised seed weight for years with cooler and cool in June, suggesting I. dichotoma might use both photosynthetic productions and underground-storage for seed maturity. Mean seed weight and seed weight variation were linked to precipitation amount whereas normalized seed weight was linked to precipitation periodicity. Seed weight variation detected delay of regrowth, caused by early drought while normalized seed weight suggested seed weight response to complete seed maturation after droughty season, using photosynthetic productions and underground-storage. The results suggest that normalized seed weight might be useful to recognize seed weight response of I. dichotoma for climatic factors, better than mean seed weight and seed weight variation.