Growth and photosynthetic responses of Gallesia integrifolia (Spreng.) Harms and Schinus terebinthifolius Raddi seedlings in dense shade |
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Authors: | Natalia S A Feijó Marcelo S Mielke Fabio P Gomes Solange Fran?a and Alyne O Lavinsky |
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Institution: | (1) Departamento de Ciências Agrárias e Ambientais, Universidade Estadual de Santa Cruz, Ilheus, BA, Brazil;(2) Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Ilheus, BA, Brazil |
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Abstract: | We analyzed the growth and photosynthetic behavior of Gallesia integrifolia (‘pau-d’alho’) and Schinus terebinthifolius (‘aroeirinha’) under shade, seeking to obtain ecophysiological information for introducing seedlings of those species in
previously established cacao agroforestry systems. Considering that light intensity under the shade of cacao trees varied
between 5 and 10% daylight, 5 months old seedlings were exposed to four irradiance levels (25, 17, 10 and 5% daylight) for
92 days. With shade increase both species displayed trends of decrease leaf mass per unit leaf area, leaf area per plant (LA),
relative growth rate (RGR) and net assimilation rate (NAR), and increase leaf area ratio (LAR). The mean values of light-saturated
net photosynthetic rate (P
nmax) in 25 and 5% daylight were 12.8 and 8.0 μmol CO2 m−2 s−1 for G. integrifolia and 17.9 and 7.4 μmol CO2 m−2 s−1, respectively, for S. terebinthifolius. Based on the measurements of photosynthetic photon flux density and estimated values of photosynthetic saturated irradiance
(Is) we concluded that, in all shaded conditions, the leaves of both species were under sub optimal light conditions to reach
P
nmax. In spite of the lowest P
nmax values, RGR and NAR were significantly higher for G. integrifolia in all irradiance levels. Differences in growth rates can be explained by the higher values of LA, LAR and leaf mass ratio
(LMR), as well as by the lower values of Is, photosynthetic compensation irradiance and dark respiration rates observed for
G. integrifolia. Even though seedlings of G. integrifolia presented higher capacity to adapt under conditions of dense shade, we concluded that both species were under stress conditions
induced by shade in light environments below 25% daylight. On a practical point of view it is possible to conclude that seedlings
of both species should be introduced in light gaps, formed after the fall of big trees, or in places in which cacao trees
are cultivated using large plant spacing. |
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Keywords: | Net photosynthetic rate Nontimber forest products Shade tolerance |
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