Influence of chromium in Laguncularia racemosa (L). Gaertn f. physiology

Abstract

(Influence of chromium in Laguncularia racemosa (L.) Gaertn f. physiology). Most studies of chromium have been realized in the sediments and in mangrove trees. However, little is known about its effect on growth and metabolism in this vegetation. L. racemosa plants were grown in solution with 20% of ionic strength of Hoagland and Arnon containing 100 mM NaCl and supplemented with 0.00, 0.05 and 0.50 mg L-1 of Cr+3. The growth, the pigments and gas exchange measurements showed no changes in response to doses of chromium. After 30 days the initiation of treatments, plants of L. racemosa had average 0.559 g of total dry weight, 1.34 mg L-1 of total chlorophyll and 7.9 μmol m-2 s-1 of A (CO2 photosynthetic assimilation). The photochemical potential efficiency was affected by the intermediate dose of 0.05 mg L-1 of Cr+3 (Fv/Fm=0.73) and it was associated with improved translocation of chromium from root to leaves. L. racemosa accumulated Cr+3 in the root, especially in the highest dose (560 mg g-1 DW) representing twenty-eight times the value obtained in control. The concentration of chromium in stem and leaves was not influenced by the tested doses. There was a reduction of fructose and sucrose in the largest dose of chromium, suggesting the drain of these carbohydrates to meet the energy demand of root absorption. The results suggest that L. racemosa owns characteristics of a chromium-tolerant species.