RESUMO
A hydroponic experiment was conducted to study the leaf cell damage and the changes in photosynthetic pigment contents of three moss species under Cd stress, aimed to reveal the Cd sensibility and tolerance of the species. Even though the Cd stress was relatively low (1 mg Cd x L(-1)), the leaf cells of Dolichomitriopsis diversiformis and Plagiomnium acutum were damaged. With the increasing level of Cd stress, the leaf cell damage of the three moss species aggravated significantly, and the resulted damage under high level (100 mg x L(-1)) Cd stress was in the order Brachythecium procumbens > P. acutum > D. diversiformis. Relatively low (1 mg x L(-1)) Cd stress had no significant effects on the total chlorophyll content of the three species. However, with the increase of Cd stress (> or = 10 mg x L(-1)), the total chlorophyll content decreased significantly, with the order of B. procumbens > P. acutum > D. diversiformis. The Cd stress at 1 and 10 mg x L(-1) had no significant effects on the chlorophyll a/b, but the Cd stress at 100 mg x L(-1) led to a significant decrease of chlorophyll a/b in P. acutum and B. procumbens. The maximal decline of carotenoid content in B. procumbens was observed at 1 mg x L(-1) of Cd. The three moss species could significantly enrich Cd, and the Cd enrichment was D. diversiformis > P. acutum > B. procumbens. The leaf cell damage rate and the changes of chlorophyll and carotenoid contents could be used to indicate the differences in the sensitivity of D. diversiformis, P. acutum, and B. procumbens to Cd stress. D. diversiformis had the strongest tolerance to Cd stress, while P. acutum and B. procumbens had weaker tolerance. The tolerance of the three moss species to Cd stress was positively correlated to the capability of their Cd enrichment.
