Responses of sensitive and tolerant bush beans (Phaseolus vulgaris L.) to ozone in open-top chambers are influenced by phenotypic differences, morphological characteristics, and the chamber environment

Responses of bush bean (Phaseolus vulgaris L.) lines 'S156' (O(3)-sensitive) and 'R123' (O(3)-tolerant), and cultivars 'BBL 290' (O(3)-sensitive) and 'BBL 274' (O(3)-tolerant) to ambient ozone (O(3)) were investigated during the 2001 and 2002 growing seasons. Seedlings were grown in pots inside open-top chambers (OTCs), with charcoal filtered (CF) and non-filtered (NF) ambient air, and in non-chambered ambient air (AA) plots. Growth parameters from individual plants were evaluated after harvests at the end of vegetative (V(4)) and reproductive (R(10)) growth phases. Results at V(4) indicated that CF did not provide additional benefits over NF in 'S156' in 2001 and 2002. In contrast, exposure to CF significantly impaired the growth of 'R123'. At the end of R(10), 'S156' produced more pods, most of which remained immature, and contained fewer seeds or were more frequently aborted, whereas pods produced in 'R123' reached pod maturation and senescence more consistently. Despite increased seed weights inside the OTCs, as observed in 'S156', differences between the two lines were insignificant when grown outside OTCs. Results from the 'BBL 290'/'BBL 274' pair, especially at V(4) phase, remained inconclusive. Plant morphological characteristics, variabilities in environmental conditions, and 'chamber effects' inside OTCs were influential in determining plant response to ambient O(3).     

Assessing the impact of ambient ozone on growth and yield of a rice (Oryza sativa L.) and a wheat (Triticum aestivum L.) cultivar grown in the Yangtze Delta, China, using three rates of application of ethylenediurea (EDU)

Foliar applications of ethylenediurea (abbreviated as EDU) were made at 0, 150, 300 or 450 ppm to field-grown rice and wheat in the Yangtze Delta in China. Rice and wheat responded differently to ambient ozone and EDU applications. For wheat, some growth characteristics, such as yield, seed number per plant, seed set rate and harvest index, increased significantly at 300 ppm EDU treatment, while for rice no parameters measured were statistically different regarding EDU application. The reason may be that the wheat cultivar used may be more sensitive to ozone than the rice cultivar. EDU was effective in demonstrating ozone effects on the wheat cultivar, but not on the rice cultivar. Cultivar sensitivity might be an important consideration when assessing the effects of ambient ozone on plants.     

Response of magnesium-deficient saplings in a young, open stand of Picea abies (L.) Karst. to elevated soil magnesium, nitrogen and carbon

A decline in a Picea abies L. (Karst.) stand in the Fichtelgebirge, NE-Bavaria, FRG has been attributed to a nutritional disharmony-a seasonal imbalance between a high supply of nitrogen, caused by high nitrogen deposition, and a low supply of soil magnesium, caused by soil acidification (Oren et al., 1988a). The nutritional disharmony hypothesis was tested on ten-year-old P. abies saplings in an adjacent stand growing on identical soil. The supply rate of magnesium relative to nitrogen was continuously increased or decreased during three successive growing seasons. Increasing the nitrogen or carbon supply resulted in a small increase in foliar nitrogen concentrations. Magnesium or carbon addition slightly raised the concentration of magnesium in the foliage. Reduction in crown leaf-area did not result in any appreciable changes in nutrient concentrations. Increased N supply decreased foliar Mg concentrations. In spite of the changes in the nutritional status of the needles, gas-exchange rates, pigment concentrations, needle characteristics and growth of twigs and stems did not differ among treatments. It appears that the growth of saplings was unimpaired at the foliar magnesium concentration at which the growth of adjacent mature trees was reduced. Moreover, it was not possible to promote nutritional disharmony in the saplings, including those receiving three times the annual nitrogen input. The study demonstrates that in young, relatively open stands of P. abies, much of the deposited nitrogen is not absorbed by the roots of saplings. Thus, the conceptual model of nutritional disharmony cannot explain forest decline if nitrogen uptake does not increase with deposition. Identifying the processes which control the uptake relative to the supply of all nutrients, and quantifying the rates of nutrient uptake are essential steps in using the conceptual model to explain specific decline symptoms.