Barry A. Logan

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Environmental stresses such as high light, low temperatures, pathogen infection and nutrient deficiency can lead to increased production of free radicals and other oxidative species in plants. A growing body of evidence suggests that plants respond to these biotic and abiotic stress factors by increasing their capacity to scavenge reactive oxygen species.(More)
To identify environmental and biological drivers of nocturnal vapour exchange, we quantified intra-annual, intra- and inter-specific variation in nocturnal water transport among ecologically diverse Eucalyptus species. We measured sap flux (J(s)) and leaf physiology (leaf surface conductance (g(s)), transpiration (E) and water potential (Psi(l))) in three(More)
The long-term effect of limiting soil nitrogen (N) availability on foliar antioxidants, thermal energy dissipation, photosynthetic and respiratory electron transport, and carbohydrates was investigated in Spinacia oleracea L. Starch, sucrose, and glucose accumulated in leaves of N-limited spinach at predawn, consistent with a downregulation of chloroplast(More)
to those exhibited by xanthophyll cycle-dependent energy dissipation. The patterns of acclimation of The acclimation of photochemistry, xanthophyll cycleglutathione reductase are discussed in the context of dependent energy dissipation, and antioxidants was the multiple roles for reduced glutathione. Catalase characterized in leaves of Cucurbita pepo L. and(More)
The temperature dependence of the relationship between the decline in activity of photosystem II (PSII) and a chlorophyll a fluorescence parameter combining the excitation pressure (1-qP) and efficiency of excitation energy capture by open PSII reaction centers in the light-acclimated state (Fv'/Fm') was investigated in cotton leaves. A formula for the(More)
Eastern dwarf mistletoe (Arceuthobium pusillum Peck) is a hemiparasitic angiosperm that infects white spruce (Picea glauca (Moench) Voss) and red spruce (P. rubens Sarg.) in northeastern North America. The effects of mistletoe infection differ substantially between white and red spruce, with white spruce suffering greater infection-induced mortality. In the(More)
Photoinactivation of photosystem 2 (PS2) results from absorption of so-called “excessive” photon energy. Chlorophyll a fluorescence can be applied to quantitatively estimate the portion of excessive photons by means of the parameter E = (F − F0′)/Fm′, which reflects the share of the absorbed photon energy that reaches the reaction centers (RCs) of PS2(More)
We investigated differences between summer and winter in photosynthesis, xanthophyll cycle-dependent energy dissipation, and antioxidant systems in populations of Mahonia repens (Lindley) Don growing in the eastern foothills of the Colorado Rocky Mountains in deep shade, full exposure, and under a single-layered canopy of Pinus ponderosa (partially shaded).(More)
Attached intact leaves of Schefflera arboricola grown at three different photon flux densities (PFDs) were subjected to 24-h exposures to a high PFD and subsequent recovery at a low PFD. While sun leaves showed virtually no sustained effects on photosystem II (PSII), shade-grown leaves exhibited pronounced photoinhibition of PSII that required several days(More)
Mastocarpus stellatus and Chondrus crispus are red macroalgae that co-dominate the lower rocky intertidal zones of the northern Atlantic coast. M. stellatus is more tolerant than C. crispus of environmental stresses, particularly those experienced during winter. This difference in tolerance has been attributed, in part, to greater contents or activities of(More)