Water deficit effects on Astragalus mollissimus and Oxytropis sericea swainsonine content, physiology, and growth.

Abstract

AbstractAstragalus mollissimus bigelovii (Amb), Astragalus mollissimus mollissimus (Amm), Astragalus mollissimus thompsonae (Amt) and Oxytropis sericea (Os) were transplanted into pots, thereafter acclimatized in a greenhouse and replanted into larger pots. Approximately 4 months after collection, they were subjected to two 21-day drought recovery cycles, followed by a final 14-day drought period. There was no species by water interaction for relative water content (RWC). Leaf RWC did not differ between water-deficit vs. well-watered plants, except in Amt, where RWC was reduced 10% under water stress. Under well-watered conditions, photosynthesis was reduced in Amb. Photosynthesis for drought vs. well-watered plants increased in Amb, but decreased in Amm and Amt, and was the same in Os. Under well-watered conditions, transpiration was highest in Amt. Under water-deficit conditions, transpiration increased in Amb, but remained the same in Amm, Amt and Os. Under both water-deficit and well-watered conditions, water use was highest in Amt and lowest in Os. Across both water treatments, water use efficiency was highest in Os. Root:shoot ratio increased with water-deficit stress across all species. Under well-watered conditions, Amb had the lowest root:shoot ratio. Under water-deficit conditions, root:shoot ratio increased in Amb and Os. Regardless of water treatment, Amm and Amt root:shoot ratio remained the same. For any of the species, total dry weight remained the same between water treatments. In water-deficit vs. well-watered plants, Amb and Amm had higher swainsonine, while Os and Amt were unaffected by water treatment. Regardless of water level, Amm produced 4- to 155-fold higher swainsonine than the other species.