Transport kinetics of ¹¹C‐labelled photosynthesis products in soybeans II. influence of salt stress

Abstract

The influence of different amounts and durations of NaCl salination of the nutrient solution on the net photosynthesis rate and the assimilate transport was studied for soybeans. In vivo measurements on the short‐time kinetics of the assimilate‐root transport were made with the short‐lived C isotope. Moderate salt stress (60 mM NaCl), with decreasing the photosynthesis rate after 7 days of treatment, did not show any influence on the assimilate transport to the main sink the root. A clear depression was observed shortly after applying a stronger salt concentration (90 mM NaCl). Stress lasting for several days at the same concentration showed a reduced photosynthesis rate, but after the plant had adapted the depression on the radioactivity translocated to the root was much reduced. A high, almost toxic salt concentration (120 mM NaCl) resulted in a drastically reduced photosynthesis rate with a similarly irreversibly restricted and time‐delayed transport rate of labelled assimilates to the root. Even with this severe salt stress in the root medium, the photosynthesis rate was not influenced in the short term.

Key words:

• Salinity
• ¹¹C‐assimilate transport kinetics
• Glycine max. (L) Merrill