Nodulation and nitrogen fixation of faba bean (Vicia faba L.) as affected by removal of the cotyledons and nitrate supply
1992
Silsbury, H. | Silsbury, J.H.
Cotyledons of faba bean (Vicia faba L. cv. Fiord) were removed to determine whether an apparent delay in nodulation of this cultivar could be attributed to an inhibitor from these organs. Cotyledons were left intact or excised from seedling plants 14 and 18 d after sowing and plants grown with or without 2-5 mM NO3(-1). Seedling growth was depressed when cotyledons were removed on day 14 but not when removed on day 18. Removal of the cotyledons at day 14 reduced nodule number and nodule weight in the absence of NO3(-1), but in the presence of NO3(-1), nodule number was unaffected and only nodule weight was reduced. Cotyledon removal at day 18 increased both nodule number and nodule weight with +NO3(-1) but not with -NO3(-1). Acetylene reduction (AR) was markedly depressed by NO3(-1). Cotyledon removal at day 14 decreased AR but removal at day 18 resulted in an increase in AR. We suggest from these results that faba bean cotyledons have an inhibitory effect on nodule activity and on nodulation and this interacts with NO3(-1). This can be explained through a 'feed-back' regulation of N2 fixation by soluble N in the seedling.
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