Soil flooding and its outcome on cadmium and nutrient uptake affect photosynthetic activity in Inga laurina plants.

Abstract

Urban areas next to mangroves are subject to progressive heavy metal contamination. Treelets of Inga laurina were collected in this ecosystem and cultivated for 30 days in waterlogged conditions and closed pots (WC) and at field capacity (FC), while exposed to different Cd concentrations (0, 50 and 100 mg·kg^-1). Soil water conditions did not affect total Cd in plants, with Cd accumulating in roots and WC inducing less leaf chlorophyll while increasing carotenoids and chlorophyll ratio. Higher net photosynthesis, stomatal conductance, transpiration, and Ci/Ca ratio were observed under the highest Cd concentration and WC, while being conservative in water consumption as shown by the reduction in both water use efficiencies. Nutritional uptake behaved differently for each element, with N, Mg and Ca not being affected by Cd under WC but K increasing with Cd. At FC, plants showed higher values than WC, with the highest Cd concentration at FC showing the highest values overall. Nutrient allocation in organs was affected by WC in N, Mg, K, P and Ca but only P by Cd, with WC reducing nutrients overall and N, Mg and Ca behaving the same in both soil conditions while K was lowered in leaves and increased in roots under WC. P allocation under WC was not hindered by Cd even showing higher values in it than FC in some treatments. Altogether, results indicate that I. laurina can be considered a Cd-tolerant species, especially in WC and it presents a potential to be used as a phytoremediator plant.