Alleviation of photoinhibition in Heliconia grown under tropical natural conditions after release from nutrient stress

We have previously reported that full sun-grown Heliconia "Golden Torch" le aves exhibited sustained decreased in PS II efficiency as compared to those grown under shade conditions. In this study, full sunlight plus low level of fertilization caused a further reduction of photosynthesis, chlorophyll content and F-v/F-m ratio while plants grown at high level of nutrient show ed higher values of all these parameters. When plants grown under intermedi ate and deep shade, there was no significant difference in all parameters i rrespective of nutrient supply. In the recovery experiments, plants without fertilizer were re-fertilized weekly. Maximal photosynthetic rates, chloro phyll content, and F-v/F-m ratio increased gradually after re-fertilizing t he plants grown under full sunlight. However, no significant changes of the se parameters were observed in plants grown under intermediate and deep sha de over the same period. Total leaf nitrogen (N) was measured parallel with all the parameters. Photosynthetic rates, chlorophyll content, and F-v/F-m ratio showed a clear linear correlation with total leaf N in plants grown under full sunlight while there was no clear relationship observed in those plants grown under intermediate and deep shade. These results suggest that acclimation of Heliconia under full sunlight could be achieved by high lev el of nutrient fertilization.