Radish (Raphanus sativus) seed size affects germination response to coumarin Williams R.D., Bartholomew P.W.* USDA-ARS-GRL, Research and Extension, Langston University, P.O. Box- 1730, Langston, OK-73050, USA. *Correspondence author: E-Mail: Paul.Bartholomew@ars.usda.gov
Online published on 7 November, 2012. Abstract The inhibition of seed germination by an allelochemical is generally greater in small seeds than in large seeds. Studies reporting these results used a large number of plant species that varied in seed size which might have introduced differences in germination characteristics or various parameters required for growth and emergence. Earlier we demonstrated that when hairy vetch (Vicia villosa Roth.) seeds were separated as to seed size, the smaller seed were more sensitive to an allelochemical, and this sensitivity was selective within a species with respect to large versus small seed. Here we confirm those observations with radish (Raphanus sativus L.) seed. Radish seedS were carefully screened into three seed-size classes: large (>2.4 mm), medium (>2.0 but <2.4) and small (<2.0 mm) seeds. Water uptake during imbibition was greater in the small seed as compared to the large and medium seed, but there was no significant difference in the final germination among the three seed sizes. When coumarin (10−3 M) was added to the uptake solution the water uptake was slightly less in the treatment solution as compared to the control (water only) solution, and this difference in uptake was more noticeable in the smaller seeds. There was no difference in the germination rate or final germination percentage between coumarin at 10−5M and the water control in the large and medium seeds. However, there was a marked statistical difference in the seed germination response to coumarin at 10−3M for all seed sizes. Seed germination was delayed and reduced by 10−3M coumarin, and the effect of the reduction in germination increased as seed size decreased. Final germination was 90%, 78% and 63% for the large, medium and small seeds, respectively. As suggested by the literature, small seed are more sensitive to allelochemicals and this sensitivity might have long term affects as to shifts in weed patterns in areas where cover-crops are used as part of the weed management system. Top Keywords Allelochemical, germination inhibition, seed size, seed weight, small seed sensitivity. Top |