Response of Alfalfa and Birdsfoot Trefoil to Shoot Removal and Root Anoxia
- A. L. Barta
Shoot removal may accentuate potential plant injury when roots are under stress. Flood-intolerant alfalfa (Medicago sativa L) and flood-tolerant birdsfoot trefoil (Lotus corniculatus L.) partition differing amounts of photoassimilate to roots during shoot regrowth, which may affect their ability to withstand stress. The objective of this study was to characterize plant response (growth and chemical composition) when root anoxia (severe hypoxia) and partial shoot removal were applied concurrently. Seedling plants (4–5 wk-old) were grown in a growth chamber using nutrient solution. Alfalfa and trefoil roots were subjected to anoxia or O2 aeration (control) with shoots either clipped to 60- to 70-mm stubble height or left unclipped. Root treatments were up to 5 d in duration. Alfalfa displayed greater damage (as measured by shoot dry matter accumulation) in response to root anoxia than did trefoil under both shoot treatments. Root anoxia significantly reduced root dry matter accumulation only in nonclipped plants, indicating that clipping had a more deleterious effect on root dry matter than did anoxia treatment. Both clipping and root anoxia had significant effects on root carbohydrates. A large increase in root sucrose concentration in response to anoxia was noted in alfalfa but not trefoil. Reducing sugar concentration declined in response to anoxia and clipping in alfalfa roots but only to clipping in trefoil roots. Root starch concentration increased in alfalfa and decreased in trefoil in response to root anoxia. There were no significant interactions between root aeration and shoot clipping in either species. Differential supply of photoassimilate did not appear to contribute to the differential tolerance to root anoxia displayed by these species. The data indicated that increased utilization of sugars may be important in trefoil's greater flooding tolerance.
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