Microdust impact on leaf gas exchange parameters in oak species of Northern Zagros forests, west of Iran

In recent years, the microdust phenomenon has greatly changed in concentration, duration and continuity as well as the frequency of occurrence in comparison with dust storms in the past which has caused a great deal of concern. Microdust is one of the most devastating factors in the environment threatening all animal and plant species. Regarding to the microdust impending threat, its ecological and economic impacts on scarce species is critical. Zagros forests act as an intrinsic filter for microdust in the western region of Iran. This study investigates the effect of microdust on oak, the most important tree in the Zagros forests. So that, three-year old seedlings of three oak species (Quercus branti, Q. libni and Q. infectoria) were exposed to microdust under natural conditions during spring and summer 2016. We examined the rate of photosynthesis, stomatal conductance, transpiration, internal CO2, mesophyll conductance, water use efficiency in control and treated plants. The results indicated that microdust had a significant impact on the examined parameters of the three oak species (P≤0.01). The gas exchange and photosynthetic rates of the treated plants were significantly reduced. In Q. infectoria, microdust had the greatest impact on photosynthesis, stomatal conductance, leaf internal CO2, transpiration and mesophyll conductance. Accordingly, microdust had a substantial influence on photosynthesis and mesophyll conductance in Q. brantii as well as the leaf internal CO2 and mesophyll conductance in Q. libani. Therefore, based on these findings, it can be concluded that microdust can disrupt the physiological activities of the examined species. Hence, continuous - exposure to microdust will accelerate the process of destruction of these forests

The impact of epicuticular wax on gas-exchange and photoinhibition in Leucadendron lanigerum (Proteaceae)

Copyright © 2006 Elsevier Masson SAS All rights reserved.This study investigated the seasonal modification of wax deposition, and the impact of epicuticular wax on gas-exchange as well as photoinhibition in Leucadendron lanigerum, a species from the Proteaceae family with wax-covered leaf surfaces and the stomata also partially occluded by wax. The results of this study demonstrated that the deposition of epicuticular wax in L. lanigerum is dependent on the age of the leaf as well as the season, and generation and regeneration of wax occur mostly in spring while transformation and also degeneration of wax crystals occur in winter. Epicuticular waxes decreased cuticular water loss, but had little impact on leaf reflectance. The temperature of leaves without wax was lower than that of wax-covered leaves, indicating that the rate of transpiration impacted more on leaf temperature than reflectance of light in the PAR range in L. lanigerum. The wax coverage at the entrance of stomata in L. lanigerum increased resistance to gas diffusion and as a consequence decreased stomatal conductance, transpiration and photosynthesis. Also, the results indicated that epicuticular waxes do help prevent photodamage in L. lanigerum, and so this property could benefit plants living in arid environments with high solar radiation. © 2006 Elsevier Masson SAS. All rights reserved.Mansour A. Mohammadian, Jennifer R. Watling, Robert S. Hillhttp://www.elsevier.com/wps/find/journaldescription.cws_home/600781/description#descriptio

Investigation of Superoxide Dismutase (SOD) Enzyme Activity, β-carotene, Total Phenol and Antioxidant Capacity in Fruit Peel of Five Citrus Cultivars under Low Temperature

Regarding the sensitivity of citrus fruit to low temperatures and the conjunction of the fruit harvest season with cold days of the year necessisates more research on physiological effects of cold-stress damages. In this study, five citrus cultivars including Sanguinelli blood orange, Local lemon, Valencia orange, Unshiu mandarin and Local orange were stored under various cold treatments (3, 0, -3 and -6 °C) at two stages of before fruit ripening and ripening. Control treatment had temperature of 15 °C. Variations of activity of superoxide dismutase (SOD), β-carotene and total phenol of fruit peel at two stages of before fruit ripening and ripening, as well as antioxidant capacity at ripening stage were examined. Results showed that under low temperature and control treatment, the SOD acivity, β–carotene and total phenol in fruit peel of the studied cultivars at ripening stage are higher than before ripening stage. In all the cultivars, except Local lemon, there was an increasing trend in the antioxidant capacity until 0 °C treatment and then became stable. The increasing trend of enzymetic and non-enzymetic antioxidants in fruit peel at ripening stage as compared with before ripening stage, was probably due to cold tolerance of fruits at this stage