Showing papers on "Plant physiology published in 2000"

Plant-environment interactions

Abstract: Genetic Manipulation The Role of Plant Hormones Light and Plant Development Acid-Soil-Stress and Plant Development Mineral Nutrition Isoprenoid Biosynthesis Whole Plant Response to Salinity Symbiotic Nitrogen Fixation Plant Response Mechanisms to Soil Compaction Plant Response to Flooding Stomata Plant Response to Air Pollution Environmental Influence of Low Temperature Photosynthetic Response Mechanisms to Environmental Change in C3 Plants Plant Respiration Responses to the Environment and Their Effects on the Carbon Balance Barriers in the Wheat Leaf Rust Pre-infection Phase.

Photosynthesis : physiology and metabolism

Abstract: Preface. Color Plates. 1. Introduction R.C. Leegood, et al. 2. The Calvin Cycle and Its Regulation W. Martin, et al. 3. Rubisco: Assembly and Mechanism H. Roy, T.J. Andrews. 4. Rubisco: Physiology in Vivo S. von Caemmerer, W.P. Quick. 5. Photorespiration R. Douce, H.-W. Heldt. 6. Metabolite Transport Across the Chloroplast Envelope of C3-Plants U.-I. Flugge. 7. Photosynthesis, Carbohydrate Metabolism and Respiration in Leaves of Higher Plants O.K. Atkin, et al. 8. Regulation of Carbon Fluxes in the Cytosol: Coordination of Sucrose Synthesis, Nitrate Reduction and Organic Acid and Amino Acid Biosynthesis C.H. Foyer, et al. 9. Starch Metabolism in Leaves R.N. Trethewey, A.M. Smith. 10. Control of Photosynthesis, Allocation and Partitioning by Sugar Regulated Gene Expression I.A. Graham, T. Martin. 11. Intercellular Transport and Phloem Loading of Sucrose, Oligosaccharides and Amino Acids C. Schobert, et al. 12. Regulation of Sugar Alcohol Biosynthesis W.H. Loescher, J.D. Everard. 13. Fructans: Synthesis and Regulation A.J. Cairns, et al. 14. Acquisition and Diffusion of CO2 in Higher Plant Leaves J.R. Evans, F. Loreto. 15. Carbonic Anhydrase and Its Role in Photosynthesis J.R. Coleman. 16. CO2 Acquisition, Concentration and Fixation in Cyanobacteria and Algae M.R. Badger, M.H. Spalding. 17. Photosynthetic Fractionation of Carbon Isotopes E. Brugnoli, G.D. Farquhar. 18. C4Photosynthesis: Mechanism and Regulation R.T. Furbank, et al. 19. Transport During C4 Photosynthesis R.C. Leegood. 20. Developmental Aspects of C4 Photosynthesis N.G. Dengler, W.C. Taylor. 21. The Physiological Ecology of C4 Photosynthesis R.F. Sage, R.W. Pearcy. 22. CO2 Assimilation in C3-C4 Intermediate Plants R.K. Monson, S. Rawsthorne. 23. Induction of Crassulacean Acid Metabolism -- Molecular Aspects J.C. Cushman, et al. 24. Ecophysiology of Plants with Crassulacean Acid Metabolism A.M. Borland, et al. Index.

Effect of Climate Conditions and Plant Developmental Stage on the Stability of Antibodies Expressed in Transgenic Tobacco

Abstract: Plants are regarded as a promising system for the production of heterologous proteins. However, little is known about the influence of plant physiology and plant development on the yield and quality of the heterologous proteins produced in plants. To investigate this, tobacco (Nicotiana tabacum cv Samsun NN) was transformed with a single construct that contained behind constitutive promotors the light- and heavy-chain genes of a mouse antibody. The in planta stability of the antibody was analyzed in transgenic plants that were grown under high and low irradiation at 15°C and 25°C. High-light conditions favored the production of biomass, of total soluble protein, and of antibody. The plants grown at 25°C developed faster and contained less antibody per amount of leaf tissue than the plants grown at 15°C. Both endogenous protein and antibody content showed a strong decline during leaf development. The heavy chains of the antibody underwent in planta degradation via relatively stable fragments. In vitro incubations of purified plantibody with leaf extracts of wild-type tobacco indicated the involvement of acidic proteases. It is interesting that the same antibody produced by mouse hybridoma cells exhibited higher stability in this in vitro assay. This may be explained by the assumption that the plant type of N-glycosylation contributes less to the stability of the antibody than the mouse-type of N-glycosylation. The results of this study indicate that proteolytic degradation during plant development can be an important factor affecting yield and homogeneity of heterologous protein produced by transgenic plants.

Changes in Cell Wall Polysaccharides During Fruit Ripening

Abstract: Softening is typically involved in the ripening process of many fruits and usually represented by a decrease in the firmness of the tissues. Softening of most fruits is accompanied by the dissolution of cell adhesion, which is brought about by the degradation of the middle lamella. In cell wall polymers, pectic polysaccharides, particularly polyuronides, have been known to be major constituents of the middle lamella. The relationship between the degradation of pectic polyuronides and the decrease in the firmness of fruit tissues has been extensively documented. Recently, in addition to the pectin degradation, xyloglucan breakdown has been observed in the early stage of softening in some fruits. These findings suggest that the degradation of both xyloglucans and polyuronides is cooperatively invohred in fruit softening processes the xyloglucan breakdown may contribute to the initiation process, while the polyuronide degradation to the excessive softening process.

Increasing fruit size in Citrus. Thinning and stimulation of fruit growth

Abstract: The importance of fruit size as a parameter of quality of citrus fruits has increased markedly in recent times. The consumer’s marked preference for large fruit causes huge differences in price between large and small fruit to the point that the income from the smaller fruit is often less than picking and hauling costs. Fruit size has become as important as yield in the determination of the profitability of citrus plantings, and an economic premium is usually obtained through the increase in fruit size even at the expense of a reduction in crop yield. This applies not only to the small fruited mandarins and hybrids but also to large fruit species such as lemons, oranges and grapefruit. To increase fruit size beyond the limits which may be obtained through the optimization of the standard cultural practices (fertilization, irrigation, pruning), several techniques have been tried such as hand thinning [80], chemical and hormone thinning [49, 77] and the hormonal stimulation of fruit growth rate by synthetic auxins [69, 70, 71]. The earlier investigations on this subject were reviewed extensively by Coggins and Hield [12], Monselise [57] and Wilson [78], which pointed out some drawbacks encountered with the use of these techniques in practice. Particularly, the application of synthetic auxins to increase fruit size often resulted in too erratic results to justify the use of these compounds by the growers [57]. An exception was the successful use of NAA and, in recent times, IZAA (5-chloroindazol-8-acetic acid; ethylcholozate) to thin satsuma mandarins in Japan [49, 50]. This success resulted from a nation wide research in which the physiological aspects of the response to these compounds were carefully characterised. In the present report, we summarise the most recent developments and our present knowledge on the way fruit size is determined and the different approaches to increase it through the use of plant growth regulators. Understanding the mode of action of the applied bioregulators shall ensure more reliable results from their application and has resulted already in the formulation of some general recommendations on their use. Some aspects on the regulation of fruit size and the response to synthetic auxins have been reviewed recently [38, 46]. Recent research carriedout in Japan has been summarised by Iwahori [54] and Yamashita [79].

Occurrence of C(3) and C(4) photosynthesis in cotyledons and leaves of Salsola species (Chenopodiaceae).

Abstract: Most species of the genus Salsola (Chenopodiaceae) that have been examined exhibit C4 photosynthesis in leaves Four Salsola species from Central Asia were investigated in this study to determine the structural and functional relationships in photosynthesis of cotyledons compared to leaves, using anatomical (Kranz versus non-Kranz anatomy, chloroplast ultrastructure) and biochemical (activities of photosynthetic enzymes of the C3 and C4 pathways, 14C labeling of primary photosynthesis products and 13C/12C carbon isotope fractionation) criteria The species included S paulsenii from section Salsola, S richteri from section Coccosalsola, S laricina from section Caroxylon, and S gemmascens from section Malpigipila The results show that all four species have a C4 type of photosynthesis in leaves with a Salsoloid type Kranz anatomy, whereas both C3 and C4 types of photosynthesis were found in cotyledons S paulsenii and S richteri have NADP- (NADP-ME) C4 type biochemistry with Salsoloid Kranz anatomy in both leaves and cotyledons In S laricina, both cotyledons and leaves have NAD-malic enzyme (NAD-ME) C4 type photosynthesis; however, while the leaves have Salsoloid type Kranz anatomy, cotyledons have Atriplicoid type Kranz anatomy In S gemmascens, cotyledons exhibit C3 type photosynthesis, while leaves perform NAD-ME type photosynthesis Since the four species studied belong to different Salsola sections, this suggests that differences in photosynthetic types of leaves and cotyledons may be used as a basis or studies of the origin and evolution of C4 photosynthesis in the family Chenopodiaceae

Response of tomato plants to chilling stress in association with nutrient or phosphorus starvation

Abstract: The experiments were conducted on two tomato cultivars: Garbo and Robin. Mineral starvation due to plant growth in 20-fold diluted nutrient solution (DNS) combined with chilling reduced the rate of photosynthesis (P N) and stomatal conductance (g) to a greater extent than in plants grown in full nutrient solution (FNS). In phosphate-starved tomato plants the P N rate and stomatal conductance decreased more after chilling than in plants grown on FNS. In low-P plants even 2 days after chilling the recovery of CO2 assimilation rate and stomatal conductance was low. A resupply of phosphorus to low-P plants (low P + P) did not improve the rate of photosynthesis in non-chilled plants (NCh) but prevented P N inhibition in chilled (Ch) plants. The greatest effect of P resupply was expressed as a better recovery of photosynthesis and stomatal conductance, especially in non-chilled low P + P plants. The F v/F m (ratio of variable to maximal chlorophyll fluorescence) decreased more during P starvation than as an effect of chilling. Supplying phosphorus to low-P plants caused the slight increase in the F v/F mratio. In conclusion, after a short-term chilling in darkness a much more drastic inhibition of photosynthesis was observed in nutrient-starved or P-insufficient tomato plants than in plants from FNS. This inhibition was caused by the decrease in both photochemical efficiency of photosystems and the reduction of stomatal conductance. The presented results support the hypothesis that tomato plants with limited supply of mineral nutrients or phosphorus are more susceptible to chilling.

Effect of light on root hair formation in Arabidopsis thaliana phytochrome-deficient mutants.

Abstract: lacking phytochrome A, phytochrome B or both (double mutant) were analyzed by comparing their photoresponse with that of the wild type. Results indicate that root hair formation in Arabidopsis was strongly stimulated by light irradiation. Both phytochrome A and phytochrome B are responsible for photoinduction by continuous red light irradiation, while only phytochrome A mediates the response under continuous far-red light. The fluence response relationships to a red light pulse in the wild type displayed a biphasic trend similar to that previously observed in lettuce seedlings, with the first phase showing a sharp maximum at 78.3 Jm−2, and the second one operating over a wider fluence range (3,100–9,400 Jm−2) two orders of magnitude higher than the first one. Analysis of the fluence response curves for red light induction in the phytochrome mutants revealed that phytochrome A is responsible for the first phase in the wild type, while the second is the result of the combined action of both phytochrome A and phytochrome B.

Chlorophyll breakdown in oilseed rape.

Abstract: Chlorophyll catabolism accompanying leaf senescence is one of the most spectacular natural phenomena. Despite this fact, the metabolism of chlorophyll has been largely neglegted until recently. Oilseed rape has been used extensively as a model plant for the recent elucidating of structures of chlorophyll catabolites and for investigation of the enzymic reactions of the chlorophyll breakdown pathway. The key reaction which causes loss of green color is catalyzed in a two-step reaction by pheophorbide a oxygenase and red chlorophyll catabolite reductase. In this Minireview, we summarize the actual knowledge about catabolites and enzymes of chlorophyll catabolism in oilseed rape and discuss the significance of this pathway in respect to chlorophyll degradation during Brassica napus seed development.

The influence of chilling on photosynthesis and activities of some enzymes of sucrose metabolism in Lycopersicon esculentum Mill

Abstract: The effects of chilling stress on leaf photosynthesis and sucrose metabolism were investigated in tomato plants (Lycopersicon esculentum Mill. cultivar Marmande). Twenty-one-day-old seedlings were grown in a growth chamber at 25/23 °C (day/night) (control) and at 10/8 °C (day/night) (chilled) for 7 days. The most evident effect of chilling was the marked reduction of plant growth and of CO2 assimilation as measured after 7 days, the latter being associated with a decrease in stomatal closure and an increase in Ci. The inhibition in photosynthetic rate was also related to an impairment of photochemistry of photosystem II (PSII), as seen from the slight, but significant change in the ratio of Fv/Fm. The capacity of chilled leaves to maintain higher qP values with respect to the controls suggests that some protection mechanism prevented excess reduction of PSII acceptors. The results of the determination of starch and soluble sugar content could show that chilling impaired sucrose translocation. The activity of leaf invertase increased significantly in chilled plants, while that of other sucrose-metabolizing enzymes was not affected by growing temperature. Furthermore, the increase in invertase (neutral and acid) activity, which is typical of senescent tissue characterized by reduced growth, seems to confirm that tomato is a plant which is not a plant genetically adapted to low temperatures.

Photosynthesis and fructose 2,6-bisphosphate content in water stressed wheat leaves.

Abstract: Net photosynthetic rates, sucrose levels, fructose 2,6-biphosphate content and the related enzyme activities were investigated in control and water stressed leaves of Triticum aestivum L. var sonalica. Fructose 2,6-bisphosphate accumulated in water stressed plants and reduced leaf photosynthesis, sucrose content and the activities of fructose 1,6-bisphosphatase and sucrose phosphate synthase. 14C-distribution into starch was more with increasing water stress while 14C-incorporation into sucrose was drastically reduced in stressed plants. Fructose-6-phosphate-2-kinase activity was extremely high in stressed plants while the activity of fructose 2,6-bisphosphatase was low. The results provide a clear evidence that low leaf water potentials result in fructose-2,6-bisphosphate accumulation, which modulates photosynthetic sucrose formation and carbon partitioning in wheat leaves.

Comparison of responses of bean, pea and rape plants to UV-B radiation in darkness and in light

Abstract: Effect of UV-B radiation on leaves of bean, pea and rape plants was studied. UV-B radiation (11.2 kJ·m−2) induced more distinct reduction of the primary photosynthesis activity when applied in darkness than the same UV-B dose, extended in time, and applied with photosynthetic active radiation (PAR). The pea plants were more susceptible to UV-B in darkness, but in the presence of PAR their tolerance was higher. The CO2 fixation in the bean and rape plants, exposed to UV-B was decreased, but for the pea plants it remained unchanged. The UV-B irradiation caused an increase in the content of ultraviolet-absorbing pigments. Additionally, the bean plants grown at UV-B increased the thickness of leaves, described as SLW.

Fine Chloroplast Structure in Cucumber and Pea Leaves Developed under Red Light

Abstract: Photosynthetic activity, the content of various photosynthetic pigments, and the chloroplast ultrastructure were examined in the leaves of cucumber (Cucumis sativus L.) and pea (Pisum sativum L.) plants of different ages grown under red light (600–700 nm, 100 W/m2). In pea leaves tolerant to red-light irradiation, chloroplast ultrastructure did not essentially change. In the first true leaves of cucumber plants susceptible to red-light irradiation, we observed a considerable increase in the number and size of plastoglobules, the appearance of chloroplasts lacking grana or containing only infrequent grana, and stromal thylakoids. In the upper leaves of 22-day-old cucumber plants, the chloroplast structure was essentially similar to that of the control chloroplasts in white light, and we therefore suppose that these plants have acclimated to red light.

Do Leaves Control Episodic Shoot Growth in Woody Plants

Abstract: ABSTRACT. It has been generally observed that leaf removal alters the pattern of episodic shoot growth in certain species in such ways that suggest some type of foliar control. In the present study, the effects of periodic defoliation during the growing season on the shoot growth of 11 woody species were analyzed in an attempt to elucidate the control mechanisms of episodic shoot growth. Four types of responses to defoliation were observed: A) A second flush in red oak, shagbark hickory, and year-old seedlings of green ash and sugar maple; B) A small continued extension of stem elongation with the production of some additional leaves and a significant delay in terminal bud formation in white ash, green ash, pignut hickory, black walnut, and in year-old seedlings of green ash and sugar maple; C) No response in sweetgum and white pine; and D) Shoot die-back in sugar maple, silver-red maple, cottonwood, black walnut, and to a lesser extent, the ashes. Defoliation was most effective and sometimes only effective in causing the above-mentioned responses when given early in the flush period. Leaf control of episodic shoot growth may be due to foliar inhibitors and/or effects of competition for water and nutrients.

Effects of shading on photosynthesis and leaf yields of ginkgo.

Abstract: Based on the four month shading test of two year seedlings of ginkgo, some morphological, photosynthetic and physiological indexes were determined. The results showed: (1) there were significant differences in leaf area per seedling among different shading treatments, with a decreasing tendency from one layer net shading, to full sun light, to two layer net shading and to three layer net shading, (2) with the increase of shading intensity, the relative water content and chlorohyll content in leaves went up markedly, (3) as for carboxylation efficiency and CO 2 compensation point, there were no remarkable differences between the treatments of one layer net shading and full sun light. However, the carboxylation efficiency decreased and CO 2 compensation point increased remarkably in the treatments of two layer net shading and three layer net shading as compared with that in full illumination, (4) in terms of apparent quantum yields of photosynthesis, there were notable differences among different treatments, with a decreasing tendency from two layer net shading, to one layer net shading, to full sun light and to three layer net shading, and (5) with the increase of shading intensity, such indexes as fresh weight per leaf area, net photosynthetic rate, light saturation point and the dried leaves weight per seedling went down apparently.