No abstract

We here describe a new hybrid within the Cyathea corcovadensis-complex: C. ×stella-matutina (C. corcovadensis s. str. × C. microdonta). We also characterize another two Cyatheaceae species from Brazil: C. mexiae (≡ Trichipteris gardneri), which has been long overlooked, and Alsophila salvinii, an Andine species recently discovered in Brazil. We provide descriptions, illustrations and comments for the three taxa. We also provide a key to the C. corcovadensis-complex, an updated key to species of Alsophila from Brazil, one lectotypification, and anatomical section images of the pinnule articulations of C. ×stella-matutina and its putative parents.

Studies on pollutant accumulation in plants are essential for the diagnosis of species with potential for revegetation and remediation of contaminated environments. Hydroponic systems are commonly used for this purpose, but little is known about the influence of the nutrient solution in the results. Borreria verticillata can be found in arsenic (As)-contaminated environments, and research using Hoagland's nutrient solution has reported a differential tolerance to the metalloid in populations from contaminated (CS) and non-contaminated (NCS) sites. However, some authors suggest the use of Clark's solution to study As tolerance in plants. We evaluated the growth and nutritional status of plants from these populations, cultivated in Hoagland's and Clark's solutions, and determined the most appropriate solution for comparative studies on tolerance to As. The selected solution was used in plant cultivation for As exposure. In Hoagland's solution plants from the NCS exhibited higher root volume, fresh and dry weight and macronutrient accumulation than those from the CS. Clark's solution promoted more similar responses and was used in plant exposure to 0, 33 and 66 lM As, for 4 days. The metalloid promoted reduction of total fresh weight in both populations. Alterations were more severe on plants from the NCS, with decreased values of root volume, gas exchanges, height and nutrient concentration in shoots. The severe damage caused by As in plants from the NCS demonstrates its sensitivity to this metalloid, while the responses of the CS population confirm the As-tolerance. These findings suggest that these populations are different ecotypes of B. verticillata.

Arsenic (As) is toxic to most living things. However, plants growing in environments contaminated by this pollutant may exhibit tolerance strategies such as restrictions to its absorption and intracellular detoxification. In the present study we compared morphophysiological responses between Borreria verticillata (L.) G.F.W. Mayer (Rubiaceae) populations from an As-contaminated site (CS) and a non-contaminated site (NCS) in order to clarify their mechanisms of As detoxification and their differential tolerance to the metalloid. Plants were grown in nutrient solution without As addition (control) and with 66 µM As for 4 days. Arsenic accumulated in plant roots, and neither bioaccumulation nor translocation factors differed between the populations. Exposure to the metalloid promoted damage to the morphology and anatomy of both roots and shoots, particularly in plants from the NCS. These plants showed more severe phytotoxic symptoms, as well as greater reduction in shoot growth and fresh biomass accumulation. Plants from the CS showed fewer toxicity symptoms due to mechanisms that favoured As detoxification and scavenging of reactive oxygen species in roots (e.g. increases in Ca and S root concentrations, higher number of phenolic and crystalliferous idioblasts and increased antioxidant enzyme activity) and the prevention of oxidative stress in leaves (through increased superoxide dismutase activity). Thus, we verified that besides the differences in P metabolism that have been reported in the literature, plants from the CS are more As-tolerant due to their higher efficiency for As detoxification, and are therefore more well suited for the revegetation of As-contaminated areas.