Diurnal changes in photoprotective mechanisms in leaves of cork oak (Quercus suber) during summer

Abstract

Daily variations in photoprotective mechanisms were studied in sun and shade leaves of 40-year-old cork oak (Quercus suber L.) trees during early summer in Portugal. Although trees were not severely water stressed because predawn leaf water potentials remained high, photosynthesis and stomatal conductance decreased at midday. The midday depression in gas exchange was not reversed by short-term exposure to "optimal" conditions of temperature, light and vapor pressure deficit. Chlorophyll a fluorescence, maximum photochemical yield of photosystem II and the quantum yield of noncyclic electron transport showed midday depressions, but recovered by the evening. Both short-term changes in the components of the xanthophyll cycle (reversible de-epoxidation of violaxanthin during the day) as well as long-term changes (higher xanthophyll content in sun compared with shade leaves) were detected and may play a role in the dissipation of excess energy at midday. Because the activities of enzymes of the antioxidant system, superoxide dismutase and ascorbate peroxidase, were high enough to cope with the increase in oxygen reactive species likely to arise under the stressful conditions of midday, we conclude that these enzymes may provide an additional mechanism for energy dissipation.

Photosynthetic analyses of two native Atlantic Forest species in regenerative understory of eucalyptus plantation

“…These responses can be seen as an important protective mechanism under conditions of water stress in S. guianensis. Similar results were observed by Faria et al (1996; in studies of the Quercus ilex and Quercus súber species, which emphasized the high degree of coordination between stomatal comportment, photosynthetic capacity, and photoprotective mechanisms. X. sericea exhibited a similar response to S. guianensis in relation to the parameters F v /F m , ΔF /F m ', and NPQ in the EXU.…”

Seasonal changes in the photosynthetic performance of two evergreen Nothofagus species in south central Chile

“…This highly efficient behavior of N. dombeyi in the utilization of absorbed energy in the photochemical and CO 2 assimilation processes at the highest PPFD (summer) coincides with higher contents in Z (8.2-fold higher) and slightly higher contents in A and L (1.9 and 1.7-fold higher, respectively) in relation to predawn (Table 2). Similar results are reported for other plants exposed to high light and to additional stresses such as drought or cold (Faria et al 1996, Logan et al 1998, Verhoeven et al 1999, García-Plazaola et al 2003. Differently as occurs in N. dombeyi, in upper canopy leaves of Nothofagus cunninghamii from an Australian rainforest subjected to high irradiance (by simulated sunflecks) the decrease of the Fv/Fm and the increase of Z, is associated with a transitory decrease of Φ PSII and net photosynthesis (Tausz et al 2005).…”

Effects of Heavy Rain during Rainy Season and Drainage Methods on Soil Water Content, Photosynthesis Characteristics, and Growth in 'Jinok' and 'Campbell Early' Grapes

“…이 방법은 포도의 수분 상태 평가 (Costa et al, 2012;Jones et al, 2002), 수분스트레스 비 교 (Gardner et al, 1981), 육종효율 증진과 자연 생태계 의 관리 및 모니터링 (Grant et al, 2012 (Grant et al, 2012;Idso et al, 1981;Jackson, 1982). 일반적으로 광합성속도와 기공전도도(stomatal conductance)간에는 높은 정의 상관관계를 나타내며 (Faria et al, 1996), 기공개폐 (Kozlowski and Pallardy, 1979;Sena Gomes and Kozlowski, 1980a;1980b;1980c)와 water vapor transfer간에는 고도로 유의한 부의관계가 성립된다 (Grant et al, 2012 Mendelssohn et al, 1981;Perata and Alpi, 1993;Saglio et al, 1980) 뿌리에서는 ATP와 ADP가 줄어들 고 (Saglio et al, 1980;Tripepi and Mitchell, 1984) 뿌리 를 통한 수체 내로의 수분 흡수가 감소하며, 기공폐쇄에 의해 기공전도도가 줄어들고 잎의 호흡량이 증가하는 등 에너지관련 대사체계가 크게 제한된다 (Liao and Lin, 1994). 또한 침수에 의한 식물의 기공폐쇄 (Kozlowski and Pallardy, 1979;Sena Gomes and Kozlowski, 1980a, 1980b, 1980c)와 그에 따른 광합성의 감소 (Beckman et al, 1992;Childers and White, 1942;Pezeshki and Chambers, 1985;Sena Gomes and Kozlowski, 1980a) 및 엽온을 기준으로 한 엽과 대기간의 확산압차 증가 (Kang et al, 2007;Naidoo et al, 1997) …”