摘要:

The appearance and development of photosynthetic activity, and the accumulation of chlorophylls, carotenoids and quinones, was investigated in etiolated barley shoots (Hordeum vulgareL. cv. Villa) during greening in flash light, periodic light‐dark cycles, and continuous white light. Greening and the development of photosynthetic activity was delayed in flash and periodic light compared to continuous white light. Photosystem II activity occurred after 6 light‐dark cycles and increased continuously during greening. After 3 h greening in continuous white light, photosystem II activity appeared with a very high rate and decreased to that of a green leaf after 50 h greening. Parallel to the development of photosynthetic activity, light stimulated the biosynthesis of prenyllipids. Moreover, chlorophylls and those carotenoids and quinones that are contained in etioplasts in relatively small amounts, were particularly enhanced in their biosynthesis. Chlorophyllawas synthesized without a lag phase during greening in flash light, whereas a 2 h lag phase occurred in continuous white light. In all three modes of illumination the formation of chlorophyllaexceeded that of chlorophyllb. After 4 flashes and 2 light‐dark cycles, chlorophyllbcould be detected with a very high initiala/bratio. Higher chlorophylla/bratios were reached after 200 flashes (a/b=10.9) and 50 light‐dark cycles (a/b=6.6) than after 50 h continuous white light (a/b=3.3). The formation of carotenes, lutein, violaxanthin and neoxanthin was also enhanced by light. This was also confirmed for plast‐ouinone‐9. ş‐tocopherol,α‐tocoquinone and phylloquinone. A comparison of the carotenoid and quinone composition of the differentiating thylakoid membrane before and after onset of photosynthesis, reveals that the photosynthetic membrane is already equipped with photosynthetic pigments and quinones before the appearance of photosystem II activity. It is concluded that during development of the photo‐synthetic apparatus the thylakoid membrane with its structural and functional constituents is formed first. In a second and slower process the water splitting enzyme system and enzymes of the Calvin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00879.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Plantago coronopusL., a species from the coastal zone, was grown in culture solution with and without 50 mMNaCl. In addition it was transferred from a non‐saline solution to a solution containing 50 mMNaCl. Short term effects of NaCl on growth and various aspects of energy metabolism, including photosynthesis, shoot dark respiration, root respiration and the contribution of the SHAM‐sensitive alternative pathway to root respiration were investigated. The concentrations of soluble and insoluble non‐structural carbohydrates and of sorbitol a compatible osmotic solute inPlantago, in both shoots and roots were also determined.Growth of shoots and roots was largely unaffected by addition of 50 mMNaCl. Net photosynthesis, shoot dark respiration and the concentration of non‐structural carbohydrates in both shoots and roots were also unaffected by salinity. The rate of root respiration immediately decreased upon addition of 50 mMNaCl. This decrease was almost exclusively attributed to a decreased activity of the SHAM‐sensitive alternative pathway. The concentration of sorbitol in the roots increased quickly after addition of 50 mMNaCl, whilst the increase in sorbitol concentration in the shoots started later. The time course of the increase of sorbitol concentration was similar to that of the decrease in activity of the alternative pathway. During the first 12 h after exposure to 50 mMNaCl, the amount of carbohydrates which was saved in respiration, due to the decreased activity of the alternative pathway, was the same as that used for sorbitol synthesis in the roots. It is concluded that the activity of the alternative pathway decreased due to increased utilization of carbohydrates for sorbitol synthesis, according to a proposed ‘energy overflow model’.After 24 h, the sorbitol concentration in the cytoplasm of the root cells of plants transferred to a saline solution reached a level that was sufficient to compensate for 50 mMNaCl, assuming a cytoplasmic volume of ca. 10% of the total cell volume. The sorbitol concentration in roots of plants grown in a saline environment for several weeks was lower than that in roots of plants transferred to a saline environment for c. 24 h. It is suggested that sorbitol accumulated in roots ofPlantago coronopusas an immediate reaction upon salinity, whilst other adaptations may occ

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00880.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The water fernAzolla pinnataR. Br. was collected in Northwestern India and its structure was examined using scanning and transmission electron microscopy. Emphasis was given to the symbiotic cyanobacterium.Anabaena azollae, and to its relationship to the hairs of the leaf cavities. The cyanobacterial filaments are loosely arranged and often adhere to the protruding hairs and the folded cell walls of the cavities. The vegetative cells show a typical bilayered cell wall. Thylakoids are few and evenly dispersed in mature vegetative cells and appear to lack phycobilisomes. Clusters of polyglucoside granules are distinguished between the thylakoids. Thylakoid membranes are often seen forming whirls and lattices. Polyhedral bodies (carboxysomes) appear particularly frequently in younger cells and in the proximity of polyphosphate bodies. Presence of structured granules, often positioned at both sides of the cross‐wall of neighbouring vegetative cells, suggest a positive nitrogen balance. A high frequency of heterocysts is noted, while spores are not observed.The outer cell wall of the unbranched, mostly two‐celled, hairs shows frequent invaginations. The cytoplasma of the mature hair contains numerous organelles, and is penetrated by an electron transparent network with blebs and vesieles appearing. The exchange of metabolites between the symbiotic partners is discussed in relation to the structures no

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00881.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Thin cell layers of tobacco (three to six layers of epidermal and subepidermal cells) were allowed to float on the surface of a liquid medium. Whereas the control on an identical medium solidified by agar gave 100% of explant‐forming flowers, no flowers formed in the absence of agar (100% of the explants formed buds). In order to initiate flower formation, various modifications of the liquid medium were tried: different ratios of indolyl‐3‐butyric acid (IBA) to kinetin (Kin) from 1 to 100, a range of pH from 4.0 to 7.0, and glass beads of different diameters (in an attempt to change the physico‐chemical characteristics of the culture substrate itself). On a liquid medium with glass beads, four types of morphogenesis (flowers, buds, a mixed programme of flowers and buds, and a non‐morphogenetic programme –i.e.the explants remained unchanged) were separately induced by changing one of the three factors: pH, IBA and Kin in equimolar concentrations, and diameter of the glass beads. Changing only the IBA/Kin ratio failed to provoke flower differentiation. pH of the medium was found to change after autoclaving and the effect of glass beads on morphogenesis was partly related to modific

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00882.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Plantago lanceolataL., a grassland species from a relatively nutrient‐poor habitat, was grown in nutrient‐rich and in nutrient‐poor culture solutions. Half of the plants were trensferred from high to low or from low to high nutrient conditions. Shoot growth was immediately reduced upon transfer to low nutrient conditions, whilst it reacted more slowly upon transfer of plants to high nutrient conditions. Root growth was less dependent on the supply of nutrients, but it was slightly reduced upon transfer of plants to high nutrient conditions.Photosynthesis was largely independent of the nutrient supply, apart from an initial increase upon transfer of plants to low nutrient conditions. Photosynthesis decreased with age in all treatments, and this decrease was not due to mutual shading. The decrease of photosynthetic rate was not accompanied by a decreased relative growth rate: it was compensated by a more efficient root respiration, since the activity of the alternative nonphosphorylating pathway continuously decreased in plants grown in a high nutrient environment.It is concluded that the alternative pathway was of significance in removal of carbohydrates, which could not be utilized for growth, energy production,etc., due to a temporary or structural imbalance between assimilate production and requirement. The alternative pathway also appeared to allowP. lanceolataplants to adapt to a changed environment as regards mineral nutrition.The experimental value for root growth respiration ofP. lanceolatagrown under high nutrient conditions was compared with a theoretical value, calculated from the biochemical composition of plant dry matter and the known energy costings for biosynthetic and transport processes. A good correlation between the experimental and theoretical value of root growth respiration was found if it was assumed that ion uptake requiredc. 1.0 molecule of ATP per ion per membrane pa

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00883.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Various aspects of nitrogen metabolism ofPlantago lanceolataL., a grassland species from a relatively nutrient poor habitat, were investigated under high nutrient conditions or low nutrient conditions. In addition the responses after switching the plants from high nutrient conditions to low nutrient conditions and vice versa were studied. The activities of nitrate reductase (NR), glutamate dehydrogenase (GDH) and glutamine synthetase (GS) were determined. In the roots they were correlated with the level of the nutrient supply. Not only NR but also GDH and GS increased upon a switch from low nutrients to high nutrients and decreased upon a switch from high nutrients to low nutrients. Reduced nitrogen content of both roots and shoots was also correlated with the nutrient supply and changed rapidly after a switch. The flexibility of the nitrogen metabolism ofPlantago lanceolatais discussed in relation to its ecological habitat.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00884.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Growth, branching and gametophore formation by protonema developing from spores of the mossPylaisiella selwyniiwere promoted by octopine, an unusual amino acid found in crown gall tumors. Cytokinin (0.01 μM) in combination with octopine (0.1 μMto 1 mM) increased the number of gametophores formed and decreased the time required for their development. The combined effect of these two compounds was similar to that obtained with virulent agrobacteria. At higher cytokinin concentrations, protonemal buds formed abnormal masses of cells rather than normal gametophores. Common amino acids and auxins, alone or in combination with cytokinin, had relatively little effect on the development of the mos

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00885.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Bicarbonate (or carbon dioxide) is required for electron transport in isolated broken pea chloroplasts. The site of action of the bicarbonate ion is between the primary electron acceptor of Photosystem 2, Q, and the plastoquinone pool. After trypsin treatment the Hill reaction with ferricyanide does not require bicarbonate. Photosystem 2 inhibiting herbicides act also at this site. Therefore, a possible interaction of bicarbonate and these herbicides in their effect on photosynthetic electron transport was studied.The reciprocal of the Hill reaction rate in CO2‐depleted chloroplasts was plotted against the reciprocal of added bicarbonate concentration in the absence and in the presence of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), 2‐methoxy‐4,6‐bis (ethylamino)‐1,3,5‐triazine (simeton) or 4,6‐dinitro‐o‐cresol (DNOC). From these Lineweaver‐Burk plots we concluded that DCMU and simeton inhibit both bicarbonate binding and Vmax. There is a purely competitive inhibition of bicarbonate binding by DNOC. We suggest that DNOC may exert its inhibition of electron transport by removing bicarbonate from its binding site.In isolated thylakoid membranes ofSynechococcus leopoliensiswe did not find a bicarbonate effect nor inhibition by DNOC after Q, indicating that in the thylakoids of this blue‐green alga the binding site for bicarbonate and DNOC between

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00886.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effects of boron‐deficient culture were studied on the unicellular diatom.Cylindrotheca fusiformisReimann and Lewin. After 24 to 30 h, cell division was almost completely inhibited in boron‐deficient cultures. By 48 h of culture, boron‐deficient diatoms had approximately twice the modal cell volume of control cells, and at least twice the amount of organic constituents such as protein (2.0x), insoluble carbohydrate (2.4x), total phenols (2.6x), and chlorophyll at (2.1x). Boron deficiency led to irreversible damage after this time.Dark respiration was 1 nmol O2/min × 106cells for both control and boron‐deficient diatoms prior to 40 h of culture. By 48 h, the respiratory rate of boron‐deficient diatoms was double that of controls. The proportion of14C‐glucose metabolized by the pentose phosphate pathway was similar in both control and boron‐deficient diatoms after 24 and 48 h of culture. After 24 h, thein vitroactivity of glucose‐6‐phosphate dehydrogenase was similar in both control and boron‐deficient cells, although the pool size of its substrate, glucose‐6‐phosphate, was 26% greater in boron‐deficient cells. The cellular amount of glucose‐6‐phosphate dehydrogenase continued to increase once mitosis was arrested in boron‐deficient diatoms. Boric acid (1 mM) inhibited 6‐phosphogluconate dehydrogenase by 18% in diatom homogenates.During the early stages of boron deficiency, the uptake of silicate, nitrate, and phosphate, and thein vitroactivity of β‐glucosidase were similar to control diatoms. After cell division was inhibited, boron‐deficient diatoms accumulated more nitrate and phosphate, and retained a higher le

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00887.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

An exo‐β‐(1β3)‐glucanase derived fromSelerotinia libertianainduced growth ofAvena sativacoleoptiles and degraded hemicelluloses and β‐(1→4):(1→3) mixed linked glucan. However, neither endo‐β‐(1→4)‐ nor endo‐β‐(1→3)‐glucanase activity could be detected in the enzyme preparation. Nojirimycin inhibited the glucan degradation caused by the enzyme but glucono‐1,5‐lactone did not. Another exo‐β‐(1→3)‐glucanase derived from Basidiomycete QM 806 did not induce coleoptile growth and did not degrade the glucan. Growth‐inducing pro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1981.tb00888.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY