Cytological observations on spruce needles after prolonged treatment with ozone and acid mist

Plastoglobule lipid bodies: their functions in chloroplasts and their potential for applications

Plastoglobules are plant lipid bodies localized inside plastids. They have long been considered as mere lipid storage compartments. However, ultrastructural and proteomic data now suggest their involvement in various metabolic pathways, notably the biosynthesis of tocopherols. In this work, the current knowledge on the structure and functions of plastoglobules is reviewed. On the basis of similarities between plastoglobules and seed oleosomes, the potential of plastoglobules for bioengineering applications is discussed.

Structural changes in the vascular bundles of light-exposed and shaded spruce needles suffering from Mg deficiency and ozone pollution

The correlation between structural changes of the vascular bundles and needle yellowing was examined for needles of damaged spruce (Picea abies (L.) Karst.) growing at a Mg-deficient and ozone polluted mountain site in the Central Black Forest (840m a.s.l.). In the previous year's sun-exposed needles, the following sequence of events was observed: (1) rapid needle yellowing, (2) hypertrophy and anomalous divisions of cambium cells, (3) phloem collapse, and, (4) production of atypical xylem tracheids. Under defined shade (reduction of the photosynthetically active photon flux density of the ambient light by 85-90%), the needles remained green, while the phloem collapsed completely within the first 6 weeks of shading; subsequently, a reversal of the collapse was observed. Under both light conditions, the content of Mg not bound to chlorophyll (Mg(free)) was in the range of 0.1 mg g(-1) needle dry matter, and hardly changed throughout the investigation period. After Mg fertilization, the Mg(free) level of the previous year's needles increased to 0.2 mg g(-1) dry matter, the light-exposed needles remained green, and the vascular bundles developed no anomalies. The data show that the rapid needle yellowing of ozone-exposed Mg-deficient needles did not depend on the collapse of the phloem. Mg deficiency played a key role in the development of anomalous vascular bundles under light, and also appears to explain the transient changes in sieve cell structure under shade. The role of Mg deficiency, rather than ozone pollution, in the damage of the sieve cells was confirmed in a long-term ozone exposure experiment with young clonal spruce growing under defined conditions.

Carbohydrate and carbon metabolite accumulation responses in leaves of ozone tolerant and ozone susceptible spinach plants after acute ozone exposure

The objective of this study was to determine whether exposure of plants to ozone (O3) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (G6P), because in leaf cells, glucose is the precursor of the antioxidant, L-ascorbate, and glucose-6-phosphate is a source of NADPH needed to support antioxidant capacity. A further objective was to establish whether the response of increased levels of glucose, sucrose, starch and G6P in leaves could be correlated with a greater degree of plant tolerance to O3. Four commercially available Spinacia oleracea varieties were screened for tolerance or susceptibility to detrimental effects of O3 employing one 6.5 hour acute exposure to 25O nL O3 L(-1) air during the light. One day after the termination of ozonation (29 d post emergence), leaves of the plants were monitored both for damage and for gas exchange characteristics. Cultivar Winter Bloomsdale (cv Winter) leaves were least damaged on a quantitative grading scale. The leaves of cv Nordic, the most susceptible, were approximately 2.5 times more damaged. Photosynthesis (Pn) rates in the ozonated mature leaves of cv Winter were 48.9% less, and in cv Nordic, 66.2% less than in comparable leaves of their non-ozonated controls. Stomatal conductance of leaves of ozonated plants was found not to be a factor in the lower Pn rates in the ozonated plants. At some time points in the light, leaves of ozonated cv Winter plants had significantly higher levels of glucose, sucrose, starch, G6P, G1P, pyruvate and malate than did leaves of ozonated cv Nordic plants. It was concluded that leaves of cv Winter displayed a higher tolerance to ozone mediated stress than those of cv Nordic, in part because they had higher levels of glucose and G6P that could be mobilized during diminished photosynthesis to generate antioxidants (e.g., ascorbate) and reductants (e.g., NADPH). Elevated levels of both pyruvate and malate in the leaves of ozonated cv Winter suggested an increased availability of respiratory substrates to support higher respiratory capacity needed for repair, growth, and maintenance.

Needle ultrastructure and starch content in Scots pine and Norway spruce after ozone fumigation

The ultrastructure of current and previous year needles of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.) Karst. was studied after exposures to several different ozone concentrations (100 to 600 nL∙L−1) and doses in a chamber system. The ultrastructural changes observed in different experiments in both of these species were qualitatively very similar. Changes were observed in the mesophyll tissue, in which increased density of chloroplast stroma and an increase of ribosome-like granules were the early symptoms, followed by a decrease of the size of chloroplasts and starch grains. Simultaneously a decline of needle starch content could be measured. After fumigation with the lower concentrations, hypertrophy of microbodies were also apparent. When the seedlings were fumigated with the highest concentration (600 nL∙L−1) a subsequent disintegration of cytoplasm and other cell organelles and finally a collapse of the contents of the mesophyll cells, leading to visible injuries, was found. Scots pine nursery stock seedlings appeared to be about equal in sensitivity to ozone as Norway spruce clonal stock. The spruce clones showed differences in sensitivity to the ozone fumigations. Since the observed symptoms are consistent in two species through a concentration gradient of ozone, and also agree with the information dealing with ozone injuries in literature, it is possible to use ultrastructural observations for diagnosing the presence of ozone injuries. Keywords: ozone, Picea abies, Pinus sylvestris, needle ultrastructure, starch.

Fatty acids and ultrastructure of ozone-exposed Aleppo pine (Pinus halepensis Mill.) needles

Fifteen or 18-month-old Aleppo pine seedlings were fumigated with different concentrations and doses of ozone over a period of 2-16 days in controlled-environmental growth chambers. The total fatty acid content and ultrastructure of the current year needles were subsequently analysed. In acute, high concentration exposures, significant reductions in the levels of linolenic acid were detected. Increases in myristic or palmitic acid were common in needles exposed to lower concentrations of ozone. Ultrastructural studies revealed reductions in chloroplast size and a darkening of stroma at low ozone exposures while at high concentrations disruption of the chloroplast membranes was also identified.