Seleção e caracterização de plantas para uso como gramados e telhados verdes

Abstract

The use of grasses for soil cover and ornamental plant species for green roofs are viable solutions to minimize impacts to the environment due to increasing urbanization. Thus, the present work aims to characterize and select accessions of Axonopus parodii and Paspalum spp. for use as ornamental grasses, considering aspects associated with the capacity of propagation by sprigs, development of seedlings, and select ornamental species with metabolism C3, C4 and CAM for use on green roofs in function of different substrate depths. For the experiment of propagation by sprigs, accessions of A. parodii (AP 01), P. lepton (PL 01) and P. notatum (PN 01, PN 02, PN 03, PN 04, PN 05 and PN 06) were cultivated to obtain grass carpets. At 98 days after planting (DAP), the carpets were sectioned to obtain the sprigs with different length. Twelve sprigs per length class (< 2 cm, 2 to 4 cm and > 4 cm) of the accessions were planted in trays with 4 replicates. As control treatment, sprigs of commercial cultivar Zoysia japonica (ZP 01) with the same lengths were used. At 63 DAP, were analyzed: survival rate of sprigs (SR in %); number of shoots (NS); lateral growth expansion (LGE in cm²); soil coverage rate (SCR in %); dry biomass of aerial part (DBAP in g); dry biomass of roots (DBR in g); and DBAP/DBR ratio. With the data obtained, correlations were made. The best results were observed from planting sprigs with more than 2 cm in length. The accessions PN 01, PN 02, PN 03 and PN 05 were selected for lawns implantation by sprigs. Based on the genotypic and phenotypic correlations, the selection of accessions for better soil coverage can be indirectly based on the higher rate of survival and less expansion since those variables are easily and quickly measure and less laborious to obtaining than dry biomass of the aerial part and root or evaluation of the soil coverage rate. For the evaluation of the development of grasses for ornamental use, six accessions of creeping growth of Paspalum spp. (PL 01, PN 02, PN 03, PN 04 and PN 05) and eight of erect growth (P. compressifolium - PC 01, PC 02 and PC 03; P. ionanthum - PI 01; P. plicatum - PPL1 , P. rhodopedum - PRH1 and PRH2, and P. rojasii - PR 01) were evaluated. At 63 DAP, the variables evaluated were: SR; NS; LGE; height (H) and SCR for accessions of creeping growth; base area and projection of the aerial part of the plant; H and SCR for erect growth accessions. At 72 DAP, the following variables were evaluated in the laboratory: fresh and dry leaf biomass; fresh and dry root biomass; fresh and dry biomass of rhizome or stolon; and root length. The creeping growth accessions PL 01 and PN 05 are recommended for use as lawns, thus as the higher fresh and dry roots, rhizomes and stolons biomass, expansion and soil coverage rate. The erect growth accessions PC 01; PC 02; PC 03; PI 01 and PPL1 were indicated as ornamental plants since its presented higher heights, aerial and root biomass and soil coverage rate from projection of the aerial part of the plant. To the evaluation of ornamental plants to use in green roof, nine species with different physiological metabolism to CO2 fixation, were cultivated in beds with 8; 10 and 12 cm depths. The species were: C3 - Begonia cucullata and Salvia nemorosa; CAM - Crassula capitella cv. Campfire; Echeveria pulvinata cv. Frosty; Sedum album, S. palmeri; Delosperma cooperi; D. cooperi cv. Orange Wonder; C4 and CAM - Portulaca grandiflora. The TS, CC, A, leaf surface temperature, flower presence and general appearance were evaluated. It was observed that the species Delosperma cooperi, D. cooperi cv. Orange Wonder and Portulaca grandiflora, with Crassulacean acid metabolism (CAM), could be indicated to green roof since it resists to high temperatures presenting good development in the different depths of the substrate maintaining high ground coverage. The species B. cucullata and S. nemorosa, with C3 metabolism, are indicated by present pleasant general appearance at different depths, good soil coverage.