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UV-B effects on growth, photosynthesis, total antioxidant potential and cell wall components of shade-tolerant and sun-tolerant ecotypes of Paubrasilia echinata

2020; Elsevier BV; Volume: 271; Linguagem: Inglês

10.1016/j.flora.2020.151679

1618-0585

Geraldo Rogério Faustini Cuzzuol, Vinícius Novo Gama, Leonardo Valandro Zanetti, Elias Terra Werner, José Eduardo Macedo Pezzopane,

Marine and coastal plant biology

The incidence of UV-B radiance on the surface of the earth has been intensifying in the tropics of the southern hemisphere. However, little is known about its effect on tropical trees, especially on sun-tolerant versus shade-tolerant plants. For this study we used two ecotypes of the tropical tree Paubrasilia echinata. These ecotypes diverge among themselves in relation to leaf morphology and ecological habitats as with respect to light availability. The small-leaf ecotype is shade-tolerant and the medium-leaf ecotype is sun-tolerant. The plants were submitted to UV-B for 45 days. The shade-tolerant ecotype proved to be negatively responsive to UV-B indicated by inhibition of stem growth, total biomass, CO2 assimilation (A) and photochemical efficiency (FV'/FM'), whereas the sun-tolerant ecotype showed to be positively responsive. This divergence of responses between the two ecotypes seems to be related to the capacity to produce phenolic compounds, total antioxidant capacity (TAC) and cell respiration (Rd). UV-B increased flavonoids, lignin, TAC and reduced Rd in the sun-tolerant ecotype. In the shade-tolerant ecotype, these responses were opposite, with increased leaf loss. As for cell wall polymers (CWP), the ultraviolet radiance increased the lignin content to the detriment of hemicelluloses in the sun-tolerant ecotype. However, it did not influence the cellulose content. In the shade-tolerant ecotype, in general, the proportions of the three CWP remained invariable in relation to the control. The results indicate that the ecotypes of P. echinata function as a good model to investigate the UV-B effects on sun-tolerant and shade-tolerant tropical trees. We presume that the increase in UV-B may be a compromise for populations of juvenile plants of the shade-tolerant ecotype and increase populations of the sun-tolerant ecotype.