physiological factors limiting germination of monogerm sugar beet seed, 1- inhibitory function of the seed cap

seed cap tightness is known to be highly associated with the low germinability of sugar beet fruits. despite, accomplishment of physiological phases of germination in germinating sugar beet seed with a tight cap, seedling emergence is usually suppress by the cap. as the seed coat (including the cap) is originated from ovary wall of the mother plant, seed cap tightness could be considered as one of the most important factor for selection of high yielding progenies. therefore, a simple technique is needed for procise assessment of the seed cap thightness. due to the problems associated with the indirect method, based on the use of the osmatic potential of pec for assessment of cap tightness (morris et al. 1985), a simple technique was developed by the author to determine the force required for seed cap removal. the similarity of the result from indirect method, (morris et. al, 1985), and that of the direct method of this study suggested that, enzymatic action on seed cap loosening is unlikely to play an important part in cap removal, and confirms therefore, the force provided via expansion of the true seed during water imbibitions is likely to be the main limitation to seed cap removal. the similarity of the result also confirms that, without facing any of the problems associated with the indirect method, the direct method could be used for seed quality control and also for selection of mother plants, which could produce high quality seed. in this study it was found that the larger the fruit, the larger the seed cap. further, it was illustrated that the direct force for seed cap removal in the large fruits was significantly more than that required for small fruits. this, more likely, could be the reason for low germinability of the large fruits. the result of this study also showed that soaking fruit for different period of time has no significant effect on the force required for cap removal.