Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/1999
Publication Date: 6/30/2000
Interpretive Summary: This research learned more about the role that stored plant carbo- hydrates played in providing supplemental nutrients for seed development when photosynthesis was reduced. Temperate grass seed yields are lower when the seed crop no longer stands upright in the field (lodged). Lodging can result from heavy wind and rain events around flowering. Lodging causes greater leaf shading and reduces photosynthesis. This condition lowers the level of stored carbohydrates in the plant and therefore has less carbohydrate available for seed development. It was found that complex and simple carbohydrates in the stem are used to a great extent to support seed development when grass seed crops lodge. Even though stem reserves can provide supplemental nutrients, some species of grass like perennial ryegrass do not have the capacity to store enough carbohydrates prior to lodging to compensate for the reduction in nutrient supply from photosynthesis when the crop is lodged. Tall fescue and Italian ryegrass on the other hand, store much more stem carbohydrates than perennial ryegrass, thus seed yield is less affected by lodging in these two species.
Technical Abstract: The adverse effect of lodging on grass seed yield may be attributed, in part, to assimilate limitation at seed sinks. This investigation examined plant dry matter, assimilate partitioning, and seed yield as affected in lodging in three species that are closely related but phenotypically different: tall fescue (Festuca arundinacea Schreber.), Italian ryegrass (Lolium multiflorum Lam.), and perennial ryegrass (L. Perenne L.). Studies were performed in field plots at Corvallis, Oregon USA. Seed yield components (seed number per inflorescence, total seed mass per inflorescence, and single seed mass) and leaf, stem (lower, middle, and peduncle), seed inflorescence dry mass were measured just prior to anthesis seed maturity. Dry mass and water soluble carbohydrates (WSC) were determi for shoot components. The reduction in dry mass and WSC in leaves and stem components following anthesis was often greater in lodged plants compared t tupright plants. The relatively low seed yield depression in lodged tall fescue suggested a higher compensation potential for partitioning reserve assimilate from leaves and stems to support seed growth and development. T potential does not appear to be present to the same degree in Italian ryegr and even less in perennial ryegrass. These findings suggest that the potent to compensate for reduced assimilate supply during the period of high assimilate demand by seeds, may be attributed, in part, to the total assimilate reserve accumulated prior to photo assimilate reduction.