Chronic ozone exposure impairs the mineral nutrition of date palm (Phoenix dactylifera) seedlings.

Chronic ozone (O3) exposure in the atmosphere preferentially disturbs metabolic processes in the roots rather than the shoot as a consequence of reduced photosynthesis and carbohydrate allocation from the leaves to the roots. The aim of the present study was to elucidate if mineral nutrition is also impaired by chronic O3 exposure. For this purpose, date palm (Phoenix dactylifera) plants were fumigated with ambient, 1.5 × ambient and 2 × ambient O3 in a free air controlled exposure (FACE) system for one growing season and concentrations of major nutrients were analyzed in leaves and roots. In addition, concentrations of C and N and their partitioning between different metabolic C and N pools were determined in both organs. The results showed that calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), sodium (Na) and potassium (K) acquisition by roots was diminished by O3 exposure of the shoot. For Ca, Mg, Fe and Zn reduced uptake by the roots was combined with reduced allocation to the shoot, resulting in a decline of foliar concentrations; for Na and K, allocation to the shoot was maintained at the expense of the roots. Thus, elevated O3 impaired both mineral uptake by the roots and partitioning of minerals between roots and shoots, but in an element specific way. Thereby, elevated O3 affected roots and shoots differently already after one growing season. However, considerable changes in total C and N concentrations and their partitioning between different metabolic pools upon chronic O3 exposure were not observed in either leaves or roots, except for reduced foliar lignin concentrations at 2 × ambient O3. Significant differences in these parameters were shown between leaves and roots independent of O3 application. The physiological consequences of the effects of chronic O3 exposure on mineral acquisition and partitioning between leaves and roots are discussed.

Foliar traits of sessile oak (Quercus petraea Liebl) seedlings are largely determined by site properties rather than seed origin.

Due to climate change, sessile oak (Quercus petraea) seedlings experience an increasing risk of drought during regeneration of forest stands by management practices. The present study was aimed at elucidating the potential of sessile oak seedlings originating from sites with different aridity and nitrogen (N) supply to acclimate to contrasting water availability. For this purpose, a free-air cross-exchange experiment was conducted between a dry and a humid forest stand with high and low soil N contents, respectively, during two consecutive years differing in aridity before harvest. Almost all structural and physiological foliar traits analyzed did not differ consistently between seed origins during both years, when cultivated at the same site. As an exception, the arid provenance upregulated foliar ascorbate contents under drought, whereas the humid provenance accumulated the phenolic antioxidants vescalagin and castalagin (VC) under favorable weather conditions and consumed VC upon drought. Apparently, differences in long-term aridity at the forest sites resulted in only few genetically fixed differences in foliar traits between the provenances. However, structural and physiological traits strongly responded to soil N contents and weather conditions before harvest. Foliar N contents and their partitioning were mostly determined by the differences in soil N availability at the sites, but still were modulated by weather conditions before harvest. In the first year, differences in aridity before harvest resulted in differences between most foliar traits. In the second year, when weather conditions at both sites were considerably similar and more arid compared to the first year, differences in foliar traits were almost negligible. This pattern was observed irrespective of seed origin. These results support the view that leaves of sessile oak seedlings generally possess a high plasticity to cope with extreme differences in aridity by immediate acclimation responses that are even better developed in plants of arid origin.