Photosynthetic and growth responses of Eugenia uniflora L. seedlings to soil flooding and light intensity

Eugenia uniflora L. (Myrtaceae) is a small tropical or subtropical shrub or tree native to South America and cultivated for different purposes in several areas of the world. It grows well in sun or partially shaded environments and is native to habitats that experience periodic soil waterlogging. The interactive effects of light intensity and soil flooding on the photosynthetic performance and growth of E. uniflora in containers were examined. Taking into account the ecological characteristics of the species, two hypotheses were tested: (a) E. uniflora seedlings subjected to soil flooding are able to maintain photosynthetic and growth rates similar to those of non-flooded seedlings and (b) photosynthetic and growth responses to soil flooding are influenced by the light environment. Seedlings pre-acclimated to full (≈44 mol m−2 day−1) and partial (≈12 mol m−2 day−1) sunlight for 55 days were subjected to soil flooding for 36 days. Photosynthetic light-response curves were analyzed for flooded and non-flooded plants two weeks after flooding and four weeks after soil drainage (unflooding plants). Plant dry weight was analyzed at the end of soil flooding period and 35 days after soil drainage. Soil flooding negatively affected the gross light-saturated photosynthetic rate expressed on an area and dry weight basis (Amax-area and Amax-weight, respectively), stomatal conductance of water vapor (gssat), and plant growth and survival. Four weeks after soil drainage, flooding also significantly reduced the apparent quantum yield (α). There were no significant interactions between flooding and light intensity on plant survival and leaf gas exchange variables, with the exception of the intrinsic water use efficiency (A/gs) four weeks after soil drainage. The effects of flooding on plant dry weight and A/gs were more pronounced in full sun than in partial sunlight and the harmful effects of soil flooding on leaf gas exchange and growth persisted after soil drainage. Changes in A/gs and α four weeks after soil drainage were interpreted as evidence of non-stomatal limitation to photosynthesis. E. uniflora is moderately sensitive to soil flooding and the effects of flooding on changes in photosynthetic performance and growth of plants are partially influenced by the light environment.