On the response of pigments and antioxidants of Pinus halepensis seedlings to Mediterranean climatic factors and long‐term ozone exposure

Abstract

An experiment was carried out in open-top chambers located in eastern Spain. One-yr-old Pinus halepensis Mill. seedlings were exposed during three consecutive summers to the following ozone (O $ ) treatments : charcoalfiltered air (CFA), non-filtered air (NFA) or non-filtered air plus 40 nl l −" O $ , 9 h d −" , 5 d wk −" (NFAj40). Seasonal variations in Aleppo pine performance were observed since reductions in chlorophyll and cellular peroxidase levels associated with increases in superoxide dismutase activity, were recorded during the summer. Similarly, a reduction in epoxidation state was found at midday during the summer, derived from an activation of the xanthophyll cycle associated to an increment in radiation and temperature levels.The first O $ -induced effects were recorded in previous-year needles (1991) during the first summer exposure as an increase in extracellular and total peroxidase activities and in zeaxanthin levels in the NFAj40 treatment along with a trend to a higher SOD activity in this treatment. A carry-over effect was detected since a lower winter recovery of chlorophyll levels was found in the NFAj40 seedlings along with a reduction of xanthophyll levels. A reduction in chlorophyll levels was observed in the previous-year needles (1992) from the NFAj40 treatment at the end of the second fumigation period. Realistic ozone exposures induced alterations in plant antioxidative systems and plant pigments as shown in this paper. These observations together with the reductions in stomatal conductance and net photosynthesis recorded in the same experiment, indicate that Aleppo pine is a species sensitive to ozone.

Drought resistance and recovery of photosystem II activity in a Mediterranean semi-deciduous shrub at the seedling stage

“…Contrary to previous studies that have related decrease in leaf Chl with reduced risk of over-excitation and photodamage in functionally different Mediterranean species such as perennial grasses (Balaguer et al 2002), evergreen sclerophylls , pines (Elvira et al 1998) as well as in mature plants of P. fruticosa (Kyparissis et al , 2000, we did not find any reduction of leaf chlorophyll content even under severe water stress. We assume that the process of Chl loss against photodamage, possibly, has not already been developed at the seedling stage of our plants.…”

On the Different Sensitivity of White Clover Clones to Ozone: Physiological and Biochemical Parameters in a Multivariate Approach

“…In the former case, O 3 could simply initiate, either directly or indirectly, pigment breakdown. In the latter one, the decrease could be regarded as an instance of acclimation, to avoid photoinhibition (Elvira et al, 1998;Kyparissis et al, 1995). This result is in accordance with other long-term O 3 exposure studies (Mikkelsen et al, 1995;Senser et al, 1990) and reports about clover clones exposed to ozone in ambient air over a long period (Heagle et al, 1993).…”

Comparative ecophysiological effects of drought on seedlings of the Mediterranean water-saver Pinus halepensis and water-spenders Quercus coccifera and Quercus ilex

“…Some authors have suggested that the decrease of photosynthetic pigment contents in stressed plants could be related to pigment photo-oxidation because of excess energy absorbed (Powles 1984;Krause 1988), while others have proposed that it could be an adaptive mechanism to prevent the absorption of excess energy. Previous studies have related avoidance of photoinhibitory damage through decreases of pigment contents (Elvira et al 1998) and/or through a reversible reorganization of PSII (Horton et al 1994;Ottander et al 1995). Among photosynthetic pigments, the loss of carotenoid content was lower than chlorophyll in water-stressed plants of all species and, consequently, the carotenoid/chlorophyll ratio increased.…”