Morphological and physiological responses of Cedrela Fissilis Vellozo (Meliaceae) seedlings to light
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Data
2006-01-01
Autores
Santos, Débora Leonardo dos
Rakocevic, Miroslava
Takaki, Massanori [UNESP]
Ribaski, Jorge
Título da Revista
ISSN da Revista
Título de Volume
Editor
Brazilian Archives of Biology and Technology
Resumo
Cedrela fissilis foi semeada e mantida em dois ambientes de luz: na margem leste (tratamento sol - razão vermelho: vermelho extremo da radiação solar direta foi 1,15) e sob dossel de floresta (tratamento sombra - radiação fotossinteticamente ativa reduzida de 0.22 a 7% da radiação direta e razão vermelho:vermelho extremo de 0,21 a 0,36). O crescimento em altura e diâmetro do caule no sol foi mais rápido, o desenvolvimento do sistema radicular continua, o número de folhas foi em média o dobro das de sombra, quanto à área foliar foi 10 vezes maior em plantas de sol com 15-25 folíolos por folha, enquanto as plantas da sombra desenvolveram de 5 a 10. Nas plantas de sombra, as maiores proporções de matéria seca foram investidas em parte aérea. A capacidade de troca de gases das plantas da sombra expostas na radiação alta não aumentou. Quando plantas de sombra foram transferidas ao sol e mantidas por 15 dias, apenas as folhas jovens se adaptaram às condições de radiação aumentada, atingindo a capacidade de resposta das folhas das plantas de sol, enquanto as folhas mais velhas caíram. As plantas de sol transferidas para a sombra não perderam as folhas, mas não atingiram a resposta das plantas de sombra.
Seeds of Cedrela fissilis Vellozo were planted and maintained under two distinct conditions: at east border of a forest with red: far-red ratio of 1.15 and under canopy with photosynthetic photon flux density of 0.22-7% of full sun radiation and red: far-red ratio of 0.21-0.36. Seedling growth (height and stem diameter) was faster under sun, the development of roots more continuous and the number of leaves almost twice of that of shade plants. The leaf area was 10 times greater in sun plants with 15-25 leaflets per leaf while under shade only 5 to 10 leaflets were found per leaf. In shade plants, a higher proportion of dry mass was found in aerial parts. Leaves of sun plants had the capacity of gas exchange to respond to high light radiation, but leaves adapted to shade presented a lower response to light changes. When shade plants were transferred and maintained under the sun for 15 days, only the young leaves were adapted to increased light radiation, reaching the same photosynthetic rate as sun plants, while old leaves were shed. Sun plants transferred to shade conditions did not lose leaves, but did not reach the same photosynthetic rate attained by shade plants.
Seeds of Cedrela fissilis Vellozo were planted and maintained under two distinct conditions: at east border of a forest with red: far-red ratio of 1.15 and under canopy with photosynthetic photon flux density of 0.22-7% of full sun radiation and red: far-red ratio of 0.21-0.36. Seedling growth (height and stem diameter) was faster under sun, the development of roots more continuous and the number of leaves almost twice of that of shade plants. The leaf area was 10 times greater in sun plants with 15-25 leaflets per leaf while under shade only 5 to 10 leaflets were found per leaf. In shade plants, a higher proportion of dry mass was found in aerial parts. Leaves of sun plants had the capacity of gas exchange to respond to high light radiation, but leaves adapted to shade presented a lower response to light changes. When shade plants were transferred and maintained under the sun for 15 days, only the young leaves were adapted to increased light radiation, reaching the same photosynthetic rate as sun plants, while old leaves were shed. Sun plants transferred to shade conditions did not lose leaves, but did not reach the same photosynthetic rate attained by shade plants.
Descrição
Palavras-chave
Photosynthesis, seedling morphogenesis, shade
Como citar
Brazilian Archives of Biology and Technology. Brazilian Archives of Biology and Technology, v. 49, n. 1, p. 171-182, 2006.