Stomatal and cuticular traits on carnation tissue culture under different ventilation conditions

Establishment of microplants is related to the moisture vapourtransmission of the culture vessel lid. In this respect, stomatal andcuticular physiology were characterized in detached leaves from Dianthuscaryophyllus grown in the glasshouse or in vitro at different rates ofventilation. In vitro plants grown in non-ventilated culture vessels hadless waxes and therefore higher RWL compared to in vitro plants grown at Vr0.86 changes.h^–1. The improvement of stomatal function inleaves obtained in ventilated vessels can be due to a performance of ionicrelations between guard and subsidiary cells, mainly by an increasingK⁺ concentration in the guard cells as ventilation decreases.Moreover, data showthat there is an increase in free ABA in the leavesfromventilated culture vessels to compensate for the conjugated ABA lostduring desiccation. If the proliferation stage proceeds in ventilatedculture vessels, the physiological characteristics of the plants producedare better than those obtained in non-ventilated culture vessels, confirmedby higher survival after soil transplantion.     

The role of calcium nutrition in potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis>) microplants in relation to minimal growth over prolonged storage <Emphasis Type="Italic">in vitro</Emphasis>

The present study investigated the effect of different levels of Ca_[ext] (0.3, 3.0, 5.0, 7.0, 9.0 and 11.0 mM) on potato over minimal growth in vitro in relation to varying water stress levels and moisture vapour transmission regimes using ⁴⁵Ca as an isotopic tracer. Ca nutrition was substantially limited when the microplants were grown at enhanced water stress level (MS + 40 g l^-1 sucrose + 20 g l^-1 mannitol) under minimal growth. Ca_[ext] in excess of standard level (3.0 mM), however, resulted in a significant increase in Ca content in microplants. The differential Ca uptake in microplants in relation to water stress and moisture vapour transmission has been discussed in terms of transpiration stream and root pressure water flow under minimal growth. The study showed that poor microplant quality at standard Ca_[ext] over prolonged storage under minimal growth was due to limiting Ca nutrition, and this could be improved by using Ca_[ext]-enriched (5.0-7.0 mM) minimal growth medium for conservation of potato microplants. The role of high Ca_[ext] in reducing the phenotypic abnormalities such as vitrification, flaccidity, hyperhydricity, etc. in potato microplants over extended storage under minimal growth has also been discussed.     

Effects of leaf wetting and high humidity on stomatal function in leafy cuttings and intact plants of Corylus maxima

When rooted cuttings of Corylus maxima Mill. cv. Purpurea are moved from the wet and humid conditions of the rooting environment, the leaves frequently shrivel and die. Since the newly formed adventitious root system has been shown to be functional in supplying water to the shoot, stomatal behaviour in C. maxima was investigated in relation to the failure to prevent desiccation. Stomatal conductance (g_s) in expanding leaves (L3) of cuttings increased almost 10-fold over the first 14 days in the rooting environment (fog), from 70 to 650 mmol m⁻² s⁻¹. In contrast, g_s of expanded leaves (L1) changed little and was in the region of 300 mmol m⁻² s⁻¹. Midday leaf water potential was much higher in cuttings than in leaves on the mother stock-plant (−0.5 versus −1.2 MPa) even before any roots were visible. Despite this, leaf expansion of L3 was inhibited by >50% in cuttings and stomata showed a gradual reduction in their ability to close in response to abscisic acid (ABA). To determine whether the loss of stomatal function in cuttings was due to severance or to unnaturally low vapour pressure deficit and wetting in fog, intact plants were placed alongside cuttings in the rooting environment. The intact plants displayed reductions in leaf expansion and in the ability of stomata to close in response to dark, desiccation and ABA. However, in cuttings, the additional effect of severance resulted in smaller leaves than in intact plants and more severe reduction in stomatal closure, which was associated with a 2.5-fold increase in stomatal density and distinctively rounded stomatal pores. The similarities between stomatal dysfunction in C. maxima and that observed in many species propagated in vitro are discussed, as is the possible mechanism of dysfunction.     

Dynamics of adaptation of stomatal behaviour to moderate or high relative air humidity in Tradescantia virginiana

Chlorophyll fluorescence imaging was used to measure stomatalclosure in response to desiccation of Tradescantia virginianaleaves grown under high (90%) and moderate (55%) relative humidities(RHs), or transferred between these humidities. Stomata in leavesgrown at high RH were less responsive to desiccation than thoseof leaves grown at moderate RH. Stomata of plants transferredfrom moderate RH conditions to high RH showed the same diminishedclosure in response to desiccation as did stomata that developedat high RH. This response was found both when the leaves werefully expanded and when still actively expanding during themoderate RH pre-treatment. Four days of exposure to high RHwas the minimal exposure time to induce the diminished closureresponse. When leaves were grown in high RH prior to a 10 dmoderate RH treatment, the reduced stomatal closure responseto desiccation was only reversed in leaves (regions) which wereactively expanding during moderate RH treatment. This indicatesthat with respect to stomatal responses to desiccation, highRH leaf regions have a limited capacity to adapt to moderateRH conditions. The decrease in responsiveness to desiccationof the stomata, induced by long-term exposure to high RH, wasnot due to osmotic adjustment in the leaves. Within 1 d aftertransferring moderate RH-grown plants to a high RH, the abscisicacid (ABA) concentration of their leaves decreased to the lowlevel of ABA found in high RH-grown leaves. The closure responsein leaves exposed to high RH for 5 d, however, could not befully restored by the application of ABA. Transferring plantsfrom high to moderate RH resulted in increased ABA levels within2 d without a recovery of the stomatal closing response. Itis discussed that the diminished stomatal closure in plantsexposed to high RH could be due to changes in the signallingpathway for ABA-related closure of stomata or to an increasedsequestration of ABA by mesophyll tissue or the symplast inthe epidermis, induced by a longer period (several days) ofa low ABA level. Key words: Abscisic acid, desiccation, PSII efficiency, relative water content, stomatal closure, vapour pressure deficit, water potential Received 8 October 2007; Revised 5 November 2007 Accepted 9 November 2007     

贵州梵净山亮叶水青冈解剖特征的生态格局及主导因子分析

使用具有不同生物学意义的生态因子为环境变量,应用多元统计方法,分析了贵州梵净山的亮叶水青冈（Ｆａｇｕｓ ｌｕｃｉｄａ Ｌ．）叶片及木材形态解剖特征的生态格局和影响其变化的主导生态因子。结果表明,随着温度要素的增加,叶片的所有解剖特征、叶表面的气孔面各以及木材的导管直径、纤维长度均显示下降趋势,而叶表面的气孔器密度、木材的导管频率和单列射线高度呈上升趋势;随着寒冷指数（负积温）和水分因子（年降水和水     

Does transpiration control stomatal responses to water vapour pressure deficit?

Three types of observations were used to test the hypothesis that the response of stomatal conductance to a change in vapour pressure deficit is controlled by whole-leaf transpiration rate or by feedback from leaf water potential. Varying the leaf water potential of a measured leaf by controlling the transpiration rate of other leaves on the plant did not affect the response of stomatal conductance to vapour pressure deficit in Glycine max. In three species, stomatal sensitivity to vapour pressure deficit was eliminated when measurements were made at near-zero carbon dioxide concentrations, despite the much higher transpiration rates of leaves at low carbon dioxide. In Abutilon theophrasti, increasing vapour pressure deficit sometimes resulted in both decreased stomatal conductance and a lower transpiration rate even though the response of assimilation rate to the calculated substomatal carbon dioxide concentration indicated that there was no ‘patchy’ stomatal closure at high vapour pressure deficit in this case. These results are not consistent with stomatal closure at high vapour pressure deficit caused by increased whole-leaf transpiration rate or by lower leaf water potential. The lack of response of conductance to vapour pressure deficit in carbon dioxide-free air suggests that abscisic acid may mediate the response.     

Effectiveness of mycorrhizal fungi on globe artichoke (Cynara cardunculus L. var. scolymus) micropropagation

The effectiveness of two arbuscular mycorrhizal (AM) fungal isolates (Glomus intraradices and Glomus viscosum) in sustaining plant growth and the physiological activities of the micropropagated globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori) were investigated during acclimatization and 90 days after plant establishment. All the mycorrhizal microplants survived transplant shock thus confirming the positive role of AM fungi colonization on ex vitro establishment. The growth increased in mycorrhizal plants, especially in plants inoculated with Glomus viscosum. Mycorrhizal plantlets showed higher stomatal conductance, which is probably necessary to supply the carbon needs of fungal symbionts. The SPAD (soil plant analysis development) data could be useful for plant management as a predictor for tissue nitrogen levels. The higher SPAD values in mycorrhizal plants are strictly related to a higher photosynthetic potential, and consequently to their better nitrogen nutrient status due to the symbiotic relationship. Regardless of the mycorrhizal performance in the host–fungus combination, the most efficient fungus for the artichoke microplants was Glomus viscosum.     

Photosynthesis in an Australian rainforest tree,Argyrodendron peralatum,during the rapid development and relief of water deficits in the dry season

Summary Rates of apparent photosynthesis were measured in situ at five positions between the upper crown and a lower branch of a 34 m tall Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas tree, and on an understorey sapling of the same species growing in a northern Australian rainforest. At the end of the dry season, rapid reductions in photosynthetic rates occurred in the upper crown within three days after a rain event, but changes in the lower crown and the sapling were less marked. Complete recovery of photosynthesis followed a second rain event. At high photon flux densities, stomatal conductance to water vapour decreased in a curvilinear fashion as the vapour pressure difference between leaf and air increased. Apparent photosynthesis was linearly related to stomatal conductance on the first clear day after each rain event, but there was no relationship between these parameters at the end of a brief natural drying cycle. Under conditions of adequate water supply, stomatal conductances of both upper crown and understorey leaves increased linearly with increasing photon flux density up to about 300 mol m^-2 s^-1. During water deficits, stomatal conductances in leaves from the understorey increased much more rapidly at very low photon flux densities than did conductances in leaves from the upper canopy.     

Stomatal Closure During Tobacco Leaf Desiccation as Affected by Ozone

The effect of acute ozone exposure on the stomatal conductance and leaf water content during rapid desiccation was examined in leaves of two tobacco cultivars, ozone sensitive cv. BelW3 and ozone tolerant cv. Samsun. The relative rate of stomatal closure was constant during leaf desiccation in cv. Samsun but decreased in cv. BelW3 in both ozonated and control plants. Ozone exposure increased the relative rate of stomatal closure and transpiration rate (measured on the following day) in cv. Samsun, but reduced the respective parameters in cv. BelW3. As a result, the plants of ozone-sensitive cultivar, treated with ozone, lost more water during desiccation than control plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of spatial heterogeneity of stomatal closure in Tradescantia virginiana altered by growth at high relative air humidity

The spatial heterogeneity of stomatal closure in response to rapid desiccation of excised well-watered Tradescantia virginiana leaves grown at moderate (55%) or high (90%) relative air humidity (RH) was studied using a chlorophyll fluorescence imaging system under non-photorespiratory conditions. Following rapid desiccation, excised leaves grown at high RH had both a greater heterogeneity and a higher average value of PSII efficiency (Phi(PSII)) compared with leaves grown at moderate RH. Larger decreases in relative water content resulted in smaller decreases in water potential and Phi(PSII) of high RH-grown leaves compared with moderate RH-grown leaves. Moreover, the Phi(PSII) of excised high RH-grown leaves decreased less with decreasing water potential, implying that the stomata of high RH-grown leaves are less sensitive to decreases in leaf water potential compared with moderate RH-grown leaves. After desiccation, some non-closing stomata were distributed around the main vein in high RH-grown leaves. Direct measurements of stomatal aperture showed 77% stomatal closure in the margins after 2 h desiccation compared with 40% closure of stomata in the main-vein areas in high RH-grown leaves. Faster closure of stomata in leaf margins compared with main-vein areas of leaves grown at high RH was related to substantially lower relative water content in these areas of the leaves.     

Anatomical Characteristics of Leaves and Woods of Fagus lucida and Their Relationship to Ecological Factors in Mountain Fanjingshan,Guizhou, China

An eco-anatomic study on leaves and woods of Fagus lucida Rehd. et Wils., which grows at an elevation of 1 260～2 020 m above sea level in Mountain Fanjingshan, Guizhou Province of Southwestern China, was carried out. Anatomical characteristics of leaves (including the thickness of upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis and lamina) and woods (vessel length, vessel width, vessel frequency, fiber length, ray width, ray height and ray frequency), and leaf surface characters (stomatal density, stomatal width and stomatal length) were determined and compared along the latitudinal gradient. As the results, 1) Lamina thickness was between 119.2 and 364.3μm; 2) Vessel frequency 75.2～133.6 per mm , vessel width 50.7～85.6 μm, vessel length 479.8～748.6 μm; fiber length 936.4～1 326.9 μm; total frequency of single and muhiseriate rays 6～9 per mm; 3) No solitary trichome was found on mature foliage, and the stomatal density was 72～113.6 per mm . Climatic indices at different altitudes were obtained by means of climatological method. Multi-statistical analysis was used to clarify the relationship between the morphological characters of the leaves and woods and climatic factors. The results showed that: 1 ) The thickness of palisade mesophyll, lower epidermis and lamina, and the vessel width increased with the humid/ add index (Bailey’s index); 2) With an increase of annual precipitation, spongy mesophyll thickness, vessel length and fiber length increased, but vessel frequency and stomatal density decreased; 3) Morphological features of leaves were closely related to low winter temperature, namely, lamina thickness decreased with coldness index, and the stomatal size decreased as the increase of mean temperature of the coldest month.     

A comparative study on growth and morphology of wasabi plantlets under the influence of the micro-environment in shoot and root zones during photoautotrophic and photomixotrophic micropropagation

The growth of wasabi (Wasabia japonica Matsumura) plantlets under different micro-environments inside culture vessels in photoautotrophic micropropagation (PA) and photomixotrophic micropropagation (PM) conditions were compared. After 28 days of culture, dry weight, relative growth rate, leaf area, and leaf chlorophyll contents of plantlets in PA were greater than those in PM. The number of leaves did not differ significantly between PA and PM conditions. PA promoted root growth and development with a greater number of roots, root length, root diameter, root fresh weight, root dry weight, and root xylem vessel system. Dissolved oxygen concentration in PA culture medium sharply decreased after 7 days of culture and then recovered. In PM culture medium, no significant fluctuation of dissolved oxygen concentration was apparent. The net photosynthetic rates of plantlets in PA were much higher than those in PM and increased with culture time. In contrast, the net photosynthetic rates of wasabi plantlets in PM kept a low and constant value during the culture period. With the presence of gas exchange membranes attached to the vessel lids, the detected vapor pressure deficit was higher in PA than in PM conditions. Higher stomatal density and larger stomatal aperture on the abaxial and adaxial surfaces of the leaves in PM medium promoted leaf water loss following ex vitro conditions. Thus, PA is applicable for producing healthy wasabi transplants.     

Effects of Humidity on Photosynthesis

It was found for two species that net carbon dioxide uptakerates were reduced at constant intercellular carbon dioxidepartial pressure when single attached leaves were exposed tolarge leaf to air water vapour pressure differences. Leaf temperature,irradiance, and ambient carbon dioxide and oxygen partial pressureswere kept constant. Net carbon dioxide uptake rates decreasedlinearly with increasing vapour pressure difference, even incases where transpiration rates were highest at intermediatevalues of vapour pressure difference. Decreases in net carbondioxide uptake rates were quickly reversible. Different windspeeds across the measured leaf, different vapour pressure deficitsaround the rest of the shoot, and transient responses of netcarbon dioxide uptake rate to abrupt changes in vapour pressuredifference all gave the same response of net carbon dioxideuptake rate to vapour pressure difference. The data show thatthe inhibition of net carbon dioxide uptake rate at a givenvapour pressure difference was not simply related to whole leaftranspiration rate or stomatal conductance. Key words: Vapour pressure difference, CO₂ uptake rate, Leaf temperature     

Photosynthesis and Transpiration as a Function of Gaseous Diffusive Resistances in Orange Leaves

The CO₂ and H₂O vapour exchange of single attached orange, Citrus sinensis (L.), leaves was measured under laboratory conditions using infrared gas analysis. Gaseous diffusive resistances were derived from measurements at a saturating irradiance and at a leaf temperature optimum for photosynthesis. Variation in leaf resistance (within the range 1.6 to 60 s cm^-1) induced by moisture status, or by cyclic oscillations in stomatal aperture, was associated with changes in both photosynthesis and transpiration. At low leaf resistance (ri less than 10 s cm^-1) the ratio of transpiration to photosynthesis declined with reduced stomatal aperture, indicating a tighter stomatal control over H₂O vapour loss than over CO₂ assimilation. At higher leaf resistance (ri greater than 10 s cm^-1) changes in transpiration and photosynthesis were linearly related, but leaf resistance and mesophyll resistance were also positively correlated, so that strictly stomatal control of photosynthesis became more apparent than real. This evidence, combined with direct measurements of CO₂ diffusive resistances (in a -O₂ gas stream) emphasised the presence of a significant mesophyll resistance; i.e., an additional and rate limiting resistance to CO₂ assimilation over and above that encountered by H₂O vapour escaping from the leaf.     

Stomatal responses to humidity in isolated epidermes

The ability of guard cells to hydrate and dehydrate from the surrounding air was investigated using isolated epidermes of Tradescantia pallida and Vicia faba . Stomata were found to respond to the water vapour pressure on the outside and inside of the epidermis, but the response was more sensitive to the inside vapour pressure, and occurred in the presence or absence of living, turgid epidermal cells. Experiments using helium–oxygen air showed that guard cells hydrated and dehydrated entirely from water vapour, suggesting that there was no significant transfer of water from the epidermal tissue to the guard cells. The stomatal aperture achieved at any given vapour pressure was shown to be consistent with water potential equilibrium between the guard cells and the air near the bottom of the stomatal pore, and water vapour exchange through the external cuticle appeared to be unimportant for the responses. Although stomatal responses to humidity in isolated epidermes are the result of water potential equilibrium between the guard cells and the air near the bottom of the stomatal pore, stomatal responses to humidity in leaves are unlikely to be the result of a similar equilibrium.     

Loss of chlorophylls, cessation of photosynthetic CO2 assimilation and respiration in the poikilochlorophyllous plant Xerophyta scabrida during desiccation

During a slow desiccation in photosynthetically fully active leaves of the poikilochlorophyllous desiccation-tolerant (PDT) monocotyledon Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae), thylakoid activity, CO₂ assimilation and respiration decline and chlorophylls and carotenoids are successively broken down. The initially slow rate of leaf water loss is related to the large reduction in leaf area which is reflected in the decrease of specific leaf area. Chlorophylls are broken down faster than carotenoids. The ratio of the variable chlorophyll fluorescence, an indicator of photosynthetic activity (Rfd690-values), shows that the functionality of thylakoids and chlorophylls is successively lost during desiccation. The decline in net CO₂ assimilation in desiccating leaves is largely caused by stomatal closure. The complete cessation of CO₂ assimilation, however, is due to the breakdown of chlorophylls and thylakoids. Respiration continued during desiccation and remained active far below -3.2 MPa leaf water potential. The differences during desiccation of the photosynthetic apparatus between poikilochlorophyllous and homoiochlorophyllous desiccation-tolerant plants are discussed.     

植物气孔扩散传导率的研究

本文对生长在可控环境温室中的花生气孔扩散传导率进行了实验研究,揭示了单个植株之间、上下表面之间、叶片不同部位以及冠层垂直方向上气孔扩散传导率的变异性。同时以气孔扩散传导率与环境条件的测定值为基础,对传导率对环境因子的反应进行了分析,植株顶部叶片气孔扩散传导率与太阳总辐射和空气饱和差有关系;冠层传导率与冠层截留辐射和空气饱和差有相关关系。     

Turning over a new ‘leaf’: multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa

Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 104 physiological and morphological traits, including gas exchange, structure and composition, hydraulic conductance, and responses to varying light, intercellular CO₂, vapour pressure deficit (VPD) and drought. Leaf types were similar in numerous traits including stomatal pore area per leaf area, leaf area‐based gas exchange rates and cuticular conductance. Each hypothesis was directly supported by key differences in function. Leaves had higher mass‐based gas exchange rates, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also showed stronger stomatal closure at high VPD, and higher maximum hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. While no single hypothesis completely explained the differences between leaf types, together the three hypotheses explained 91% of differences. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts.     

The effect of atmospheric humidity on photosynthesis,transpiration and water use efficiency of leaves of several plant species

The effect of humidity on the gas exchange of leaves of the dicotyledons soybean (Glycine max (L.) Merrill), sunflower (Helianthus annuus L.), jojoba (Simmondsia chinensis (L.) Schneider), and saltbush (Atriplex halimus L.) and the monocotyledons wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) sorghum (Sorghum bicolor (L.) Moench) and barnyard grass (Echinochloa crus-galli (L.) Beauv.) was examined under conditions of adequate soil moisture in a controlled environment. Photosynthesis and stomatal and internal diffusion resistances of whole, attached, single leaves were not affected by changes in humidity as the vapour pressure deficit between the leaf and atmosphere ranged from 8 to 27 mb. Transpiration increased linearly with increasing vapour pressure deficit. Whole plants of barley exhibited a different response. As humidity was increased, photosynthesis increased, transpiration expressed per unit of vapour pressure difference increased, and diffusion resistances became smaller. Reasons for the different behaviour of single leaves and whole plants are suggested. An index for water use efficiency, expressed per millibar of vapour pressure deficit, was calculated for single leaves of each species used in the experiments. This showed that water use efficiency was highest in the C₄ xerophytes and lowest in the C₃ mesophytes. The effect of environment on water use efficiency is examined using data from the literature.