Aclimatação de mudas de acariquara à alta irradiância

Abstract

Resumo -O objetivo deste trabalho foi determinar as mudanças fisiológicas que ocorrem em acariquara (Minquartia guianensis) durante o processo de aclimatação à alta irradiância, bem como a estratégia de aclimatação dessa espécie. Plantas mantidas em baixa irradiância foram transferidas para alta irradiância por 290 dias. Durante esse período, foi medida a relação entre fluorescência variável e máxima (F v /F m ), em folhas desenvolvidas à sombra e, após a senescência prematura por foto-oxidação, em folhas aclimatadas ao sol. Ao final do experimento, foram determinadas as características fotossintéticas e anatômicas da folha. A exposição à alta irradiância causou, logo após a transferência, forte fotoinibição e foto-oxidação parcial da folhagem, mas não provocou a morte da planta. Folhas produzidas no ambiente ensolarado apresentaram valores de F v /F m similares aos do controle. A fotossíntese saturada por luz e a fotossíntese saturada por CO 2 foram 90 e 50% maiores em plantas aclimatadas à alta irradiância. A velocidade máxima de carboxilação da rubisco e a taxa máxima de regeneração da ribulose bisfosfato seguiram a mesma tendência. Folhas produzidas ao sol apresentaram maior densidade estomática e maior espessura foliar. A produção de folhas novas é a principal estratégia de aclimatação da acariquara à alta irradiância.Termos para indexação: Minquartia guianensis, características da folha, características fotossintéticas, fluorescência da clorofila, fotoinibição. Acclimation of manwood seedlings to full sunlightAbstract -The aim of this work was to determine the physiological changes that occur in manwood (Minquartia guianensis) during the acclimation process to high irradiance, and also to determine the acclimation strategy of this species. Plants kept in low light were transferred to high irradiance for 290 days. During this period the ratio between variable fluorescence and maximum fluorescence (F v /F m ) was measured in leaves developed in the shade, and after premature senescence due to photooxidation, in sun-acclimated leaves. At the end of the experimental period the anatomic and photosynthetic characteristics of leaves were determined. Exposure to high irradiance caused, just after transferring, strong photoinhibition and partial photooxidation, but did not cause plant death. Leaves produced in sunny environment showed F v /F m similar to that of control plants. Light-saturated photosynthesis and CO 2 saturated-photosynthesis were 90 and 50% higher in plants acclimated to high irradiance. The maximum carboxylation velocity of rubisco and the maximum rate of ribulose bisphosphate regeneration followed the same trend. Leaves produced under sunlight had higher stomatal density and increased leaf thickness. The production of new leaves is the main acclimation strategy to high irradiance in manwood.

Morphological and physiological adjustments of Brazilwood (Caesalpinia echinata Lam.) to direct solar radiation

“…The fast reduction in F V /F M of C. echinata under high irradiance was also observed in other tropical trees under intense irradiance Magalhães et al, 2009). Similarly, the recovery time of F V /F M was also fast, especially when compared to other tropical species, such as Minquartia guianensis (Magalhães et al, 2009) and Aniba rosaeodora , whose recovery time was 30 and 60 days, respectively.…”

“…The fast reduction in F V /F M of C. echinata under high irradiance was also observed in other tropical trees under intense irradiance Magalhães et al, 2009). Similarly, the recovery time of F V /F M was also fast, especially when compared to other tropical species, such as Minquartia guianensis (Magalhães et al, 2009) and Aniba rosaeodora , whose recovery time was 30 and 60 days, respectively. For C. echinata, the recovery of the maximum quantum yield of primary photochemical reactions of PSII, the number of Q A reduced by RCs in the antenna chlorophyll of PSII (RC/ABS) and performance index (PI ABS ) started in the last three days prior to abscission and was completed on the 20 th day in the new leaflets.…”

“…The decrease in the ratios Chl a:b and Chl total :Carot in plants of C.echinata after periods of exposure to direct sunlight (Figure 4) is one of the immediate responses of shade species when exposed to higher irradiance (Demmig-Adams and Adams, 2006;Morais et al, 2007;Magalhães et al, 2009) light-gathering antennas (Kitajima and Hogan, 2003;Laisk et al, 2005;Magalhães et al, 2009). This strategy protects the photosystems from photo-oxidative damage caused by high irradiance (Tan et al, 2000;Marenco et al, 2001;Reyes-Díaz et al, 2009).…”

How does Cariniana estrellensis respond to different irradiance levels?

“…However, this was insufficient to increase the carbon inflow and net photosynthesis. This suggests inhibiting rubisco activity due to higher leaf temperatures associated with elevated irradiance (Law and Crafts-Brandner 1999), as observed with other tropical species when exposed to high luminosity (Dias and Marenco 2007;Magalhães et al 2009) or to photo-damage of the lower chloroplastidics pigments concentration and higher dissipation of light energy (DI 0 / RC). The photo-protection strategies of C. estrellensis under low and high light intensities suggest that it has high competitive capacity in the different forest environment, which could explain its ability to expand over areas of Atlantic Forest (Barros et al 2012).…”

SPAD-502 readings in response to photon fluence in leaves with different chlorophyll content

“…Besides its importance in harvesting light energy, leaf chlorophyll content is a sensitive indicator of plant stress (Havaux & Tardy, 1999;Zarco-Tejada et al, 2002), hence, changes in the chlorophyll/carotenoid ratio can be used as indicators of oxidative stress (Magalhães et al, 2009). As there is a close relationship between chlorophyll content and leaf nitrogen concentration, leaf greenness has been used to estimated leaf nitrogen content in several crops, such as maize (Chapman & Barreto, 1997), coffee (Torres- Netto et al, 2005), and Brachiaria brizantha (Batista & Monteiro, 2007).…”