The objective of the present work was to assess whether the depression of photosynthetic activity in
droughted Lupinus albus L. plants was more closely associated with carbohydrate build-up or ABA
accumulation. With that purpose we have measured the concomitant drought-induced changes in photosynthetic
capacity and the concentrations of Rubisco, chlorophylls, non-structural carbohydrates and ABA in young and
old leaves of white lupin plants. Although Rubisco and chlorophylls contents did not decrease with water stress,
the photosynthetic capacity was decreased by soil drying, the decline in photosynthesis being more tighly related
with ABA accumulation than with sugar content. In contrast to droughted plants, ABA feeding to intact plants
resulted in a significant decrease in Rubisco and chlorophyll content. However, no increase in shoot ABA
content was detected in ABA-fed plants. Therefore this work is not conclusive as to the correlation between
photosynthetic capacity and ABA accumulation in droughted white lupin plants being causal or not
