Transpiration of detached leaves from mycorrhizal and nonmycorrhizal cowpea and rose plants given varying abscisic acid, pH, calcium, and phosphorus

 Vesicular-arbuscular mycorrhizal (VAM) colonization can alter transpiration of host leaves, but scientists remain unclear about the mechanisms involved. We tested whether intact root systems were required to observe effects of root colonization by Glomus intraradices on leaf transpiration, or whether some VAM influence resided in leaves even after they were detached from root systems. We measured the transpiration of detached leaves of VAM and nonmycorrhizal plants exposed to different levels of several substances known to influence stomata locally or act in whole-plant regulation of transpiration: abscisic acid, calcium, phosphorus, and hydrogen ions. In rose, some VAM influence on transpiration resided in leaves, even after they had been separated from their root systems. However, removing leaves from their root systems eliminated the VAM influence on stomatal behavior of cowpeas. Accepted: 22 June 1998     

Translocation of 14C, carbohydrate content and activity of the enzymes of sucrose metabolism in rose petals temperatures

Both export of ¹⁴C from the source leaves of roses (Rosa × hybrida cv. Golden Times) and import of ¹⁴C to the petals were reduced by plant exposure to low night temperature. However, the import was affected to a greater extent than the export. During all stages of flower bud development the concentration of reducing sugars in petals of roses grown at reduced night temperature was lower than in petals of plants grown at higher night temperature. There was no significant difference in starch content in response to the night temperature, and the content of starch decreased toward complete flower bud opening. The concentration of sucrose in flowers at the low night temperature remained low during all stages of flower bud development, while at the high night temperature the concentration of sucrose increased during flower bud development, reaching a peak at the stage when petals start to unfold. At both temperatures the concentration of sucrose declined at complete flower opening. The activity of sucrose synthase (EC 2.4.1.14) was inhibited by low temperature in young rose shoots more than in the petals, while the activity of acid invertase (EC 3.2.1.26) was affected similarly in both tissues by the temperature treatments.     

The effect of root temperature on rose plants in relation to air temperature

Rose plants (Rosa hybrida ‘Sonia’=‘Sweet Promise’) were grown in heated (minimum night temperature 17°C), and unheated greenhouses with or without root heating to 21°C. These trials covered 6 growth cycles extending over two winter seasons. In the heated greenhouse, root heating did not increase yield, flower quality or plant development. In the unheated greenhouse, root-heated plants grew as well as those in the air-heated greenhouse as long as the air temperature did not fall below 6°C. When minimum night temperatures fell below 6°C, growth, yield and quality were reduced, irrespective of root temperature. Daytime plant water relations were studied in plants growing at 6 different root temperatures in the unheated greenhouse. Leaf resistance to water diffusion was lowest at optimal root temperature. Total leaf water potential was not significantly affected by root temperature.     

Water relations and xylem transport of nutrients in pepper plants grown under two different salts stress regimes

Two iso-osmotic concentrations of NaCl and Na₂SO₄ were used for discriminating between the effects of specific ion toxicities of salt stress on pepper plants (Capsicum annuum L.) grown in hydroponic conditions, in a controlled-environment greenhouse. The two salts were applied to plants at different electrical conductivities, and leaf water relations, osmotic adjustment and root hydraulic conductance were measured. Leaf water potential (_w), leaf osmotic potential (_o) and leaf turgor potential (_p) decreased significantly when EC increased, but the decrease was less for NaCl- than for Na₂SO₄-treated plants. The reduction in stomatal conductance was higher for NaCl-treated plants. There were no differences in the effect of both treatments on the osmotic adjustment, and a reduction in root hydraulic conductance and the flux of solutes into the xylem was observed, except for the saline ions (Na⁺, Cl^– and SO₄ ^2–). Therefore, pepper growth decreased with increasing salinity because the plants were unable to adjust osmotically or because of the toxic effects of Cl^–, SO₄ ^2– and/or Na⁺. However, turgor of NaCl-treated plants was maintained at low EC (3 and 4 dS m^–1) probably due to the maintenance of water transport into the plant (decrease of stomatal conductance), which, together with the lower concentration of Na⁺ in the plant tissues compared with the Na₂SO₄ treatment, could be the cause of the smaller decrease in growth.     

Relationship between potassium fertilisation and nitrate assimilation in leaves and fruits of cucumber (Cucumis sativus) plants

The effect of application of different potassium rates on some parameters of nitrate metabolism and yield in cucumber plants (Cucumis sativus) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of applications of K⁺ at three rates in the form of K₂SO₄ (Kl: 0.075 mg ml^?1, K2: 0.15 mg ml^?1, and K3: 0.30 mg ml^?1). The results showed a positive effect of higher K⁺ fertilisation (0.30 mg ml^?1) on uptake, translocation and reduction of NO₃^? in leaves compared with the lowest K⁺ rate. In addition, the higher K⁺ rates strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, thereby perhaps also enhancing the maximal commercial yield. In conclusion, for improved cucumber cultivation under greenhouse conditions, 0.15 mg ml^?1 of K⁺ gave maximal yield, while the application of 0.30 mg ml^?1 increased the metabolism and efficient utilisation of NO₃^?.     

Lipid composition in leaves of cucumber genotypes as affected by different temperature regimes and grafting

The lipid composition of leaves has been investigated in different genotypes of cucumber ( Cucumis sativus L.), which differ in temperature requirement for cultivation. In addition the effects of hardening by low but non-chilling temperature, soil heating and grafting (on the chilling-resistant C. ficifolia L.) on lipid composition have been studied. Content and composition of phospholipids and sterols were determined as well as phospholipid/sterol ratio, and fatty acid composition of total lipids and the different phospholipids.
The effects of genetic differentiation and of the various culture treatments on lipid composition of the leaves were very different. Genetic differentiation was evident as higher levels of Iinolenic acid in several phospholipids in the more cold-tolerant cultivars. Hardening the plants by low temperature resulted in a higher phospholipid level (especially phosphatidyl choline), more unsaturated phospholipid, and lowering of the sterol/phiospholipid ratio, all properties which may contribute to a higher membrane fluidity and lower growth temperature limit. Soil healing reduced the phospholipid level of the leaves slightly, and a higher content of 3- trans -hexadece-noic acid in phosphatidyl glycerol was observed. Grafting cucumber on the cold-resistant rootstock of C. ficifolia also raised the level of trans -hexadecenoic acid in phosphatidyl glycerol. The role of this fatty acid in the functioning of the chloroplast is discussed.     

不同管理模式对茶树碳氮磷含量及其生态化学计量比的影响

植物不同器官的碳(C)、氮(N)、磷(P)含量及其生态化学计量特征能够反映植物内部的养分分配与平衡关系。该研究以福建安溪3种不同管理模式的铁观音茶园为研究对象, 设置了常规管理模式下的茶园(M1)、间作套种模式下的茶园(M2)和现代技术管理模式下的茶园(M3) 3种样地, 分析茶树根、茎、叶器官的C、N、P含量及其化学计量学特征, 养分的变异特征与异速生长关系。结果表明: M2和M3管理模式下茶树根、茎、叶N、P含量均显著高于M1管理模式, C含量差异不明显; 茶树根、茎、叶C:N、C:P、N:P均表现为M1 > M2 > M3。茶树不同器官C、N、P含量差异较大, 根据变异来源分析, 管理模式因素对C、N、P含量变异的影响均达到显著水平。根茎叶N-P的异速生长关系表明茶树不同器官的养分需求存在相似性; 土壤pH和容重是影响C:N、C:P、N:P的重要因素, 而土壤含水量和盐度对茶树根和叶C含量的影响较大。总体来讲, 间作套种以及现代化滴灌、水肥等管理模式可以改善茶树对养分的吸收效率, 对解决土壤养分不均衡问题具有正面效应。     

The effect of caffeine,different fixation regimes and low temperature on microtubules in the cells of higher plants

Caffeine, (1:3:7-tri-methyl-xanthine), either as a prefixation treatment or included with glutaralde-hyde as the primary fixative, destroys or disorganises the microtubules associated with the formation of secondary walls in fibres from the flowering stem of the grass Lolium temulentum L. There is no observable effect of caffeine treatment on the microtubules associated with primary wall formation in collenchyma and young fibres from L. temulentum or in root cap cells of Zea mays L. and Phaseolus vulgaris L. The microtubules associated with primary wall formation are destroyed by cold treatment but not those associated with secondary wall formation. Tannic acid included in the fixative shows the microtubules associated with secondary wall formation in fibres of L. temulentum to be composed of 13 subunits. Treatment with lanthanum hydroxide does not stain the core or the halo of the microtubules.Abbreviation PIPES Piperazine N-N- bis 2 ethanol sulphonic acid The Grassland Research Institute is financed through the Agricultural Research Council     

Source metabolism dominates the control of source to sink carbon flux in tuberizing potato plants throughout the diurnal cycle and under a range of environmental conditions

The aim of this work was to investigate the effect of environmental conditions on the control of source to sink carbon flux in potato during tuberization. Top down metabolic control analysis was used to quantitatively determine the extent to which source and sink reactions control the flux from CO₂ to the tuber. Under all conditions investigated (beginning of the dark period, low nitrogen availability, variation in temperature) source metabolism accounts for at least 80% of the control. In plants grown with limiting nitrogen, or when measurements were made at low temperature the extent to which source metabolism controls flux increased to 90%.     

Effect of night temperature on daytime stomatal conductance in early and late successional plants

Summary Sixteen annuals, biennials, and herbaceous and woody perennials characteristic of early and late successional old field ecosystems and upland and floodplain habitats were analyzed for their response of stomatal conductance to changes in night temperature. Early successional species that germinate in early spring when temperatures are low, but above freezing are insensitive to cool nights, i.e., their conductance in the following days is unaffected by low night temperature. Later spring and summer-emerging species' stomatal conductance is inhibited by low temperatures. Tree species show the same effects and in some an enhancement of stomatal conductance by low night temperatures was observed. However, adaptive differences in response to night temperatures appear related to both phenology of germination and growth and habitat types.     

Effect of root zone carbon dioxide enrichment on ethylene inhibition of carbon assimilation in potato plants

Potato plants ( Solanum tuberosum L. var. Russet Burbank) treated with 1 μl ethylene 1⁻¹ of air showed an inhibition of CO₂ assimilation by 18%. The inhibition occurred after 3 h of exposure to ethylene and was not mediated through closure of the stomata. The enrichment of the root zone with CO₂ almost completely abolished the ethylene inhibition of CO₂ assimilation which was apparently due to an increase in the intercellular concentration of CO₂ in leaves following enrichment. The effect of application of CO₂ to the root zone on ethylene inhibition of CO₂ assimilation seemed to last for a few days. Potato plants treated with aminoethoxyvinlglycine (AVG) showed an increase in fresh and dry weight as compared to non-treated plants. Our results indicate that both CO₂ and AVG alter the effect of ethylene and promote growth in plants by inhibiting ethylene action and biosynthesis, respectively.     

Influence of high temperature on carbon assimilation,enzymatic antioxidants and tuber yield of different potato cultivars

High temperature is one of the major limiting factors for cool season crops like potato in many parts of the world. This problem is more aggravated in early season planting of potato crop. This study was conducted to evaluate the performance of five potato cultivars (Solanum tuberosum L. cultivars Kufri jyoti, Kufri megha, Kufri pokraj, Rangpuria and Badami) under normal (mid October–mid January) and early season (mid August–late October) conditions during two consecutive years in terms of carbon assimilation, activities of antioxidant enzymes and tuber yield. Temperature during growth of early season crop remained 2–14°C higher than in the normal season crop, which imposed severe heat stress on early season crop. However, this heat stress in early season crop caused several folds increase in the activity of antioxidant enzymes, which had strong positive correlation with tuber yield. Although tuber yield of all tested cultivars was less in early season than in normal season; nonetheless cultivars Kufri megha and Rangpuria performed better in early season planting owing to higher net photosynthesis, carotenoid contents, membrane stability, and activities of enzymatic antioxidant enzymes. In crux, carotenoids, activities of enzymatic antioxidants, carbon assimilation and membrane stability may be used as physiological markers in future breeding programs aimed to improve the heat resistance in potato.     

Effect of different densities of the twospotted spider mite Tetranychus urticae on CO2 assimilation, transpiration, and stomatal behaviour in rose leaves

The effect of population density of Tetranychus urticae Koch on CO2 assimilation, transpiration and stomatal behaviour in rose leaves and on the diameter and length of stems and flower buds was investigated under greenhouse conditions. The investigation was performed in order to gain more insight into integrated control systems in rose crops grown under greenhouse conditions. Physiological processes, such as photosynthesis and transpiration, as well as stomatal behaviour and chlorophyll content, were studied as they form part of the plant's nutrition mechanism and therefore affect the quantity and quality of the flowers. Information related to the effect of spider mite population density on bloom quality, diameter and length of stems and flower buds was also collected. The data indicate that increased mite density coincides with a decrease in the net photosynthetic rate, transpiration and chlorophyll content. Higher mite densities on leaves cause stomata to remain open for longer periods, which allows a greater loss of water. Spider mite densities of 10 and 50 mites per leaf cause a reduction in flower stem length of 17 and 26%, respectively, as compared to plants with no mites present.     

Reduction, assimilation and transport of N in normal and gibberellin-deficient tomato plants

A fast-growing normal and a slow-growing gibberellin-deficient mutant of Lycopersicon esculentum (L.) Mill. cv. Moneymaker were used to test the hypothesis that slow-growing plants reduce NO₃^? in the root to a greater extent than do fast-growing plants. Plants that reduce NO₃^? in the root may grow more slowly due to the higher energetic and carbon costs associated with root-based NO₃^? reduction compared to photosynthetically driven shoot NO₃^? reduction. The plants were grown hydroponically with a complete nutrient solution containing 10 mM NO₃^? and the biomass production, gas exchange characteristics, root respiratory O₂ consumption, nitrate reductase activity and translocation of N in the xylem were measured. The gibberellin-deficient mutants accumulated more total N unit^?1 dry weight than did the faster-growing normal plants. There were no significant differences between the genotypes in the rates of photosynthesis expressed on a leaf dry weight basis. The plants differed in the proportion of photosynthetic carbon available to growth due to a greater proportion of daily photo-synthate production being consumed by respiration in the slow-growing genotype. This difference in allocation of carbon was associated with differences in the specific leaf area and specific root length. In addition, a greater leaf weight ratio in the fast-growing than in the slow-growing plants indicates a greater investment of carbon into biomass supporting photosynthetic production in the former. We did not find differences in the activity or distribution of nitrate reductase or in the N composition of the xylem sap between the genotypes. We thus conclude that the growth rate was determined by the efficiency of carbon partitioning and that the site of NO₃^? reduction and assimilation was not related to the growth rate of these plants.     

Effect of oxygen and temperature on the efficiency of photosynthetic carbon assimilation in two microscopic algae

The CO₂ compensation points of Coccochloris peniocystis, a blue-green alga and Chlamydomonas reinhardtii, a green alga, were determined at pH 8.0 in a closed system by a gas chromatographic technique. The compensation point of Chlamydomonas increased markedly with temperature, rising from 0.79 microliter per liter CO₂ at 15 C to 2.5 microliters per liter CO₂ at 35 C. In contrast, the compensation point of Coccochloris at 20 C was 0.71 microliter per liter CO₂ and rose to only 0.95 microliter per liter CO₂ at 40 C.     

Effects of temperature on phyllody expression and cytokinin content in floral organs of rose flowers

Formation of leaf-like organs known as phylloids in Rosahybrida cv. Motrea flowers was promoted by exposure of plants toelevated temperatures. At a day/night temperature regime of26°C/21°C respectively theproportion of malformed flowers exhibiting phyllody was four times higher thanthat in flowers of plants grown at21°C/15°C. The number ofpetals in phyllody-expressing flowers was higher than that in normal flowers.The total content of endogenous cytokinins in young flower buds of plantsexposed to the lower temperature was six times higher than that at the highertemperatures. The effects of the reduced temperature were pronounced on all thegroups of cytokinins examined. However, the proportion of the various cytokiningroups remained similar at both temperature regimes. In contrast to thecytokinins in the flower buds, the content of all cytokinin types in youngleaves increased following exposure to the higher temperature and was reducedbythe lower temperatures. After 11 weeks at the lower temperature, about18% of the flowers remained malformed, whereas at the higher temperatureabout 20% of the flowers still remained normal. All thephyllody-exhibiting flowers were formed on vigorously grown basal shootscharacteristic to Rosa hybrida plants, whereas the normalflowers at the elevated temperatures were formed on lateral shoots which weremost distal to the plant base. However, irrespective of the season, thepresenceof normal and malformed flowers was observed on plants kept growing at standardconditions of 30°C/17°C inthegreenhouse. This phenomenon led us to examine the cytokinins in floral organsofnormal and malformed cv. Motrea flowers grown in the greenhouse as well as inflowers of a complete rose mutant known as a 'Green Rose(Rosa chinensis viridiflora). The highest content ofcytokinins was found in the pistils and stamens of normal 'Motreaflowers. On the other hand, the content of cytokinins in leaf-like style-tubesin the malformed flowers as well as in partially malformed ovaries at the baseof phylloids was significantly lower. A low content of cytokinins was alsopresent in petals of both normal and phyllody-exhibiting flowers and the lowestcontent has been found in the phylloids of the 'Green Rose. Apossibility of mutant deviations in metabolism of cytokinins in rose plants isdiscussed.     

Effect of different light qualities on the ultrastructure, thylakoid membrane composition and assimilation metabolism of Chlorella fusca

Chlorella fusca (Shihira et Krauss) strain C-1.1.10 was grown under three different light qualities (red, white or blue light) in homocontinuous cultures. Under electron microscopy, blue light cultures showed enlarged cells, thinner cell walls and lower starch content than red light cells. Under blue light, the degree of stacking of the thylakoid membranes was significantly lower than under white or red light conditions. Changing the light from blue to red the ratio of exposed to appressed membranes was doubled. Compared to red light cells, blue light cells exhibited higher photosynthetic rates per chlorophyll molecule and contained less chlorophyll per dry weight. Blue light stimulated the content of soluble protein as well as that of soluble carbohydrates. The dry weight productivity per unit time was enhanced under blue light conditions. The thylakoid protein complexes which are generally assumed to be localized in the exposed membranes were found in higher concentrations under blue light than under red light. In blue light, both the Photosystem II/Photosystem I ratio and the ratio of light-harvesting chlorophyll protein to P-700 chlorophyll a -protein were lower than in red light. Blue light cells contained twice the concentration of cytochrome f , which correlates well with their higher photosynthetic capacity. When altering the light quality, the degree of change in the reaction center complexes was much lower than expected given the corresponding degree of change in the ratio of exposed to appressed membranes. These results are discussed in light of the question as to whether the variation in the stoichiometry of the laterally distributed complexes can be explained by changes in the degree of stacking alone.     

陆地生态系统碳源与碳汇及其影响机制研究进展

全球碳循环研究中发现,目前已知碳源与碳汇不能达到平衡。存在一个很大的碳失汇。大气、海洋和陆地生态系统是人工源CO2的3个可能的容纳汇,其中陆地生态系统最复杂、最具不确定性,因此陆地生态系统碳源与碳汇研究是全球碳循环研究的核心问题之一。大气成分监测、CO2通量测定、森林资源清查以及模型模拟等方面的研究都表明,CO2施肥效应、氮沉降增加、污染、全球气候变化以及土地利用变化,是影响陆地生态系统碳储量的主要生态机制,但不确定在过去的10～100年以及未来哪一种机制起最主要的作用。     

Effect of cadmium on growth and respiration of barley plants grown under two temperature regimes

We studied cadmium effect on the respiratory pathways ratio in the organs of barley (Hordeum distichum L., cv. Novichok) plants grown in water culture at two temperature regimes. Mineral nutrients were supplied daily in exponentially increasing amounts in order to provide for steady-state growth. CdSO₄ (30, 60, or 100 μmol/l) was added to nutrient solution at a single time in the beginning of the exponential growth period (19 days after germination). In further 6 days, the relative growth rate and biomass accumulation declined stronger with the increase in the cadmium concentration in plants grown at 13/8°C (day/night) than at 21/17°C (day/night). Cadmium suppressed root respiration (down to 60% of control) stronger than leaf respiration, and the roots manifested a higher sensitivity to the inhibitor of alternative oxidase, salicylhydroxamic acid. The respiratory pathways ratio in the roots occurred against the background of activated lipid peroxidation (POL). The highest POL activity and the highest proportion of alternative respiration pathway (AP) (up to 46% of total respiration) were observed in the roots in the presence of the highest cadmium concentration (100 μM) under lower temperature (13/8°C). Thus, high cadmium concentrations affected strongly the total rate of respiration and respiratory pathways ratio. Growth temperature modulated Cd effects on respiration. AP activation is one of the mechanisms for maintenance of root cell homeostasis under cadmium-induced stress.     

连作马铃薯植株库源关系及其对块茎产量的调节机理

甘肃中部沿黄灌区是国内重要的加工型马铃薯生产基地和种薯繁殖基地,但集约化生产带来的连作障碍已严重影响到产业的健康发展.为揭示马铃薯连作障碍机理,本研究通过田间试验,设置马铃薯连作年限为0～5年的处理,研究了马铃薯植株库容量、库活性和源活性对连作的响应特征及其对块茎产量的调节机制.结果表明: 短期连作(1～2年)条件下块茎产量较非连作(0年)无显著变化,长期连作(3～5年)显著下降28.6%～32.8%,单薯质量降低是导致块茎产量下降的直接原因.长期连作马铃薯库容量较非连作显著降低38.4%～53.0%.长期连作导致块茎形成推迟,同时单薯干物质积累量降低.长期连作也显著降低马铃薯源活性,与非连作相比,株高、主茎分枝数、叶绿素含量和叶片干物质量均显著下降,根系形态发育受到抑制,根系活力显著下降28.6%～63.1%,叶片RuBP羧化酶和蔗糖磷酸合成酶活性分别显著下降52.6%～64.6%和26.3%～53.4%.长期连作条件下马铃薯源端生产性能降低导致同化产物减少,花后阶段向块茎的输入不足,降低块茎产量.库源关系失衡是甘肃中部沿黄灌区长期连作马铃薯产量大幅降低的原因.