Increased Leaf Water Potential Research Articles

Graphene promotes the growth of Vigna angularis by regulating the nitrogen metabolism and photosynthesis.

Graphene has promising applications in agriculture and forestry. In the current study, six different concentrations of graphene (0mg/L, 0.01mg/L, 0.10mg/L, 1.00mg/L, 10.00mg/L, and 100.00mg/L) were used to investigate its effect on the growth and development of V. angularis plants in soil culture. The results showed that the group treated with 1.00mg/L graphene (G-1) had significantly increased plant height (19.86%), stem diameter (24.33%), and leaf area (13.69%), compared to the control group (CK). Moreover, all concentrations of graphene had positive effects on the total root length, total root surface area, and the number of root tips of V. angularis. Compared to the CK group, the G-1 group had significantly increased leaf water potential (37.89%), leaf conductivity (2.25%), and SOD, POD, and CAT activities (47.67%, 35.22%, and 199.3%, respectively). The G-1 group also showed improved leaf net photosynthetic rate, chlorophyll content, and soluble sugar content (51.28%, 24.25%, and 38.35%, respectively), compared to the CK group. Additionally, 1.00mg/L graphene led to a 23.88% increase in the podding rate and a 17.04% increase in the yield of V. angularis plants. The rhizosphere soil of V. angularis treated with 1.00mg/L graphene had a 25.14% increase in hydrolyzable nitrogen content and a 66.67% increase in available phosphorus content. RNA-seq data indicated that 1.00mg/L graphene induced the expression of photosynthesis and nitrogen transmembrane transport genes, including ATP synthase subunit b, photosystem I reaction center subunit XI, photosystem I reaction center subunit IV A, ferredoxin, and psbP-like protein 1, as well as genes for photosynthesis antenna proteins, glutamine synthetase, glutamate dehydrogenase 1, cyanate hydratase, protein fluG-like, and NRT1/PTR family, suggesting that graphene promoted the growth and development of V. angularis by enhancing the photosynthesis and nitrogen metabolism processes in V. angularis plants. Our results indicated that a suitable concentration of graphene could significantly promote the growth of V. angularis plants in soil.

Effect of soil drought stress on leaf water status and photosynthetic apparatus in argan seedlings (Argania spinosa)

Argan tree growth and production are both affected by drought stress, which is recognized as a critical and serious environmental issue worldwide. This study aims to examine the effect of a multi-species consortium of arbuscular mycorrhizal fungi (AMF) “Rhizargan consortium”, on the leaf water status and photosynthesis in drought-stressed argan seedlings. The performances of Rhizargan consortium were compared to those of a single pure commercialized strain of Rhizophagus irregularis. Seedlings of two argan tree ecotypes were subjected to three water regimes: 30, 60, and 100% field capacity (FC). After twelve months of drought stress, mycorrhizal argan seedlings showed a significant increase in leaf water potential, stomatal conductance, and maximum efficiency of PSII (Fm/Fv) than those without mycorrhiza inoculation. Moreover, AMF inoculation led to significant leaf accumulation of chlorophyll and carotenoid upon drought imposition. Nonetheless, severe drought stress (30% FC) decreased these physiological/photochemical attributes as well as both frequency and intensity of mycorrhization, but to a lesser extent in the argan seedlings inoculated with “Rhizargan consortium”. This study contributes to advances in the knowledge of the indigenous Rhizargan consortium’s ability to induce drought tolerance in argan trees.

Nitrogen addition alleviates drought effects on water status and growth of Moso bamboo (Phllostachys edulis)

Forest ecosystems are increasingly exposed to climate-change-induced drought and nitrogen deposition. However, the role of nitrogen deposition in shaping the responses of plant water use and growth to drought remains unclear. In this study, we conducted an ecosystem-scale manipulation experiment with sixteen plots of 400 m2 to explore responses of water use and growth patterns in a Moso bamboo (Phllostachys edulis) forest to throughfall reduction treatment (TRT) (-50%) and nitrogen (N) addition (100 kg ha−1 yr−1 of nitrogen) for two years. We found that TRT significantly reduced daily total canopy transpiration (EL), leaf water potential, leaf area index (LAI) and basal area increment in a unit stand area (BAI) by decreasing hydraulic conductance (K) and photosynthetic rate. N addition pronouncedly caused lower EL and higher LAI due to increased stomatal conductance sensitivity to vapor pressure deficit, photosynthetic rate, and intrinsic water use efficiency (WUEi) as well as decreased ratio of cross-sectional area of the culm wall to total leaf area (AS/AL) and root/ leaf ratio. The interaction of TRT and N addition caused an increase in leaf water potential at midday (20.6%) and BAI (+25%) compared with the TRT, accounting for the increased stomatal conductance sensitivity, K, photosynthetic rate and WUEi. Our results suggest that N addition alleviates drought effects on foliar water state and growth of Moso bamboo through altered stomatal conductance sensitivity, hydraulic architecture, and photosynthesis. Our findings highlight the key role of coupling processes of forest carbon, nitrogen and water in shaping plant water use and growth, suggesting that interactive effect of drought and nitrogen deposition on plant hydraulic properties should be considered under a changing environment.

Effects of Severe Drought Stress on Some Physiological and Biochemical Parameters of AMF Inoculated C. arietinum

In this study, physiological and biochemical changes caused by mycorrhizal symbiosis in chickpea plants under drought conditions were investigated in both root and leaf. Drought stress reduced leaf water potential, but mycorrhizal symbiosis caused a significant increase in leaf water potential. However, the application of mycorrhiza under drought stress caused an increase in the amount of elements that are very important for the development of the plant in the root and leaf. In our study, drought increased the proline concentration and MDA content, while mycorrhiza application decreased them in both leaf and root. In addition, while mycorrhizal application increased the activity of catalase, it decreased the activity of superoxide dismutase. In general, enzyme activities were found to be higher in the leaf, but no distinct pattern was obtained between root and leaf in other analyzes. The study shows that the responses of mycorrhizal symbiosis in chickpea plants may change depending on the severity of the drought. Especially antioxidant enzyme activities and proline content patterns reveal that more comprehensive studies should be conducted on these issues. However, continuing studies until determining the effects of AMF symbiosis on grain yield under drought may provide more comprehensive results.

Atmospheric CO2 enrichment effect on water use efficiency in chickpea (Cicer arietinum L.)

AbstractEffect of atmospheric CO2 enrichment on crop water relations was evaluated in an open‐top chamber experiment on kabuli chickpea (Cicer arietinum L.; Pusa 1,105). Increase in atmospheric CO2 concentration (e[CO2], 580 ± 20 μmol/mol) resulted in 21%–46% increase in leaf water potential, and 7%–11% in relative leaf water content, indicating higher water content in leaves, compared to the ambient level (a[CO2], 384 ± 12 μmol/mol). Higher leaf water status was connoted through spectral indices over the growing period. A rise in CO2, however, brought increase in leaf diffusive resistance and canopy temperature by 15%–35% and 3%–11%, respectively, potentially indicating partial closure of stomata. Increase in leaf area index (13%–73%), and higher spectral vegetation index suggested improved growth of chickpea under e[CO2]. An increase in leaf area compensated the decrease in diffusive resistance, and therefore seasonal total water use was similar between enriched and ambient conditions. Although water use efficiency (WUE) increased by 30% (p < .05) due to an increase in crop biomass under e[CO2], the canopy conductance remained unaffected. Results suggest a possibility of improved plant water status, enhanced biomass production and increased WUE for chickpea, with similar crop water use under future e[CO2] levels.

Physiological and Productive Response of Two Varieties of Tomato (<i>Solanum lycopersicon</i>) to the Application of <i>Glomus iranicum</i> in the Region of Extremadura

Two varieties of tomato plants, H 1015 (1) and H 3402 (2) from two adjoining commercial farms located in San Benito, Extremadura and cultivated in the same soil and fertirrigation conditions, were inoculated with the arbuscular mycorrhizal fungus Glomus iranicum variety Tenuihypharum, (AMF) from the commercial product Mycogrowth. The applied treatments to the plants were: control 1, AMF 1, control 2 and AMF 2. The physiological indicators and productive responses of the plants from the four treatments were studied. The percentage of mycorrhization, soil moisture, the growth of dry aerial biomass, leaf water potential (Ψ leaf), stomatal conductance (gs), photosynthetic rate (Pn) and performance of its components rate were evaluated 81 days after transplantation. The (Ψ leaf) and (Pn) were measured twice (10.00 and 13.00 h). The results showed that symbiosis between tomato plants and the AMF was successful. Plants of both varieties treated with AMF, had better physiological performance, increased leaf water potential, increased gas exchange (stomatal conductance and photosynthetic rate), and showed improvements in growth, quality and productivity at plot level. The positive effects of this fungus show that it could result of great importance for reducing the use of chemical fertilizers, at least partially, in the future.

Application of Paclobutrazol to Mitigate Environmental Stress of Urban Street Trees

Paclobutrazol is a tree growth regulator that is frequently applied by arborists to control tree growth in utility rights of way. Paclobutrazol is also marketed to mitigate tree stresses associated with urban environments. In this study we applied paclobutrazol as a soil drench to honeylocust (Gleditsia triacanthos L var. inermis (L.) Zab.) and Callery pear (Pyrus calleryiana Decne.) trees planted as street trees on two sites in Lansing, Michigan USA. We evaluated physiological and morphological responses for two years after treatment. Application of paclobutrazol increased SPAD chlorophyll index of trees of both species in both years, compared to untreated control trees. Application of paclobutrazol increased leaf water potential of trees on one study site (Downtown) but not the other (Old Town). Paclobutrazol increased gas exchange (net photosynthesis and stomatal conductance) of Callery pear trees on one of four measurement dates (gas exchange was not measured on honeylocust trees). Leaf size of Callery pear trees was reduced following paclobutrazol application whereas leaf size of honeylocust trees was unaffected by paclobutrazol. These results indicate that paclobutrazol can help to reduce stress of trees and improve physiological function under urban conditions. However, paclobutrazol should be viewed as part of a suite of options for arborists and landscapers to manage trees on stressful sites, rather than as a replacement for proper overall care.

Tillage system affects soil water and photosynthesis of plastic-mulched maize on the semiarid Loess Plateau of China

Water deficit is a threat to agricultural sustainability in the semiarid Loess Plateau of China due to low and variable precipitation. Technologies to improve soil water content (SWC) are necessary for sustainable intensification of maize production. The potential of plastic film mulch and reduced tillage to improve SWC has been reported for the Loess Plateau. However, there has been little research on how tillage management can be integrated with plastic mulching as an approach to improve SWC and maize photosynthesis. A 3-yr field study was conducted to investigate how tillage system influences SWC, photosynthetic performance, grain yield, and grain water use efficiency (WUEg) of plastic-mulched maize in a semiarid environment. Treatments were conventional tillage (CT), rotary tillage (RT), subsoiling (SS), and no-till (NT). Soil water content in the 0–30 cm depth with SS was 24, 31, and 13% greater at the flowering, kernel milk, and physiological maturity stages of maize phenological development, respectively, compared to CT. These improvements in SWC were associated with increased leaf water potential (17%), net assimilation rate (41%), transpiration rate (54%), and stomatal conductance (42%), and decreased intercellular CO2 concentration (15%) and stomatal limitation (20%) with SS compared to CT. Subsoiling used more water (9%) and increased grain yield by 21% compared to CT, thus enhancing WUEg by 11%. On average, reduced tillage systems had improved performance (SS > NT > RT > CT) for almost all parameters measured. These results show that SS is a viable option for increasing grain production of plastic-mulched maize in semiarid areas.

Stress physiology and metabolism in hybrid rice. I. Organic manures improve physical soil characteristics and drought tolerance

ABSTRACTThe present era is witnessing a serious water crisis affecting rice (Oryza sativa) productivity adversely. Therefore, with the objective of minimizing crop failure under limited water supply the effects of organic manures were compared with inorganic fertilizer for changes in soil physical characteristics, morpho-physiological traits and drought resistance of hybrid rice NDRH-2. Accordingly, one level each of green manure and compost (7.5 t ha−1) was applied supplemented with chemical fertilizers to bring them nutritionally at par with inorganic fertilizer treatment. Organic manures minimized the adverse effect of drought on plant height during a 10-day soil-drying cycle. Organically fertilized treatments enhanced plant sustenance by 4-7 days during drought compared with that fertilized inorganically. Sustenance enhancement was probably due to increased soil moisture-holding capacity [26% to 27.4% in organically fertilized soil (OFS) against 22.2% in inorganically fertilized soil (IFS)] because of decreased soil bulk density (1.20g mL−1 OFS against 1.42 IFS) and soil penetration resistance (500 to 560 kPa OFS against 800 kPa IFS). The organic manures significantly increased leaf water potential (−16 to −18.5 bars OFS against −25 bars IFS), relative water content (84 to 85% OFS against 78% IFS), cell viability (OD 0.290 to 0.352 OFS against 0.165 IFS), membrane stability (83 to 87% OFS against 75%IFS), chlorophyll (10.06 mg g−1 dry weight OFS against 9.42 IFS) and reduced leaf injury (score 3 to 4 OFS against 5 IFS) causedby drought. Hence, farmers living in drought-prone regions, are advised to practice organic farming using organic manures for a successful rice crop in event of scanty rainfall.

Nano-ZnO priming induces salt tolerance by promoting photosynthetic carbon assimilation in wheat

ABSTRACT High salt seriously reduces plant growth in wheat by depressing photosynthetic carbon assimilation. In this study, wheat plants were firstly primed with nano-ZnO (50 mg L−1), and after 20-day recovery, the plants were then exposed to a 10-day salt stress (200 mM NaCl). The nano-ZnO priming significantly reduced Na concentration and increased leaf water potential under salt stress. In relation to the non-primed plants, the nano-ZnO primed plants possessed more effective oxygen scavenging system as exemplified by the enhanced activities of SOD, APX and CAT, leading to a better maintenance in homeostasis of ROS production under salt stress. The nano-ZnO priming benefited the tolerance of photosynthetic apparatus to subsequent salt stress, which was mainly due to the enhanced trapped energy flux and electron transport flux. The nano-ZnO priming increased the activities of phosphoglucomutase and cytoplasmic invertase, which promoted the sucrose biosynthesis in leaves under salt stress. In addition, the nano-ZnO primed plants had higher shoot dry weight than the non-primed plants under salt stress. Collectively, nano-ZnO priming activated the antioxidant system to depress the oxidative burst and enhanced the efficiency of photosynthetic electron transport and sucrose biosynthesis in leaves under salt stress, hereby improved the salt tolerance in wheat.

Foliar water-uptake strategies are related to leaf water status and gas exchange in plants from a ferruginous rupestrian field.

Fog is a frequent event in Brazilian rupestrian field and plays an important role in the physiology of several plant species. Foliar water uptake (FWU) of fog may be fast or slow depending on the species. However, fog water may negatively affect CO2 assimilation. Thus, the interference in the water and carbon balance as a result of different strategies of FWU was evaluated to verify whether fog may mitigate possible water deficit in leaves. Four plant species with different FWU strategies were studied in a ferruginous rupestrian field with frequent fog. Gas exchange and water potential were measured before dawn and at midday during the dry and rainy seasons, separating foggy from non-foggy days during the dry season. The FWU speed negatively influences CO2 assimilation in the dry season, possibly because of its negative relationship with stomatal conductance, since reduced stomatal aperture impairs carbon entrance. Fog presence increased leaf water potential both in early morning and midday during the dry season. However, during the rainy season, the values of leaf water potential were lower at midday, than during the dry season with fog at midday, which favors leaf gas exchanges. FWU interferes negatively, but briefly with CO2 assimilation. Nevertheless, FWU prevents water loss through transpiration and increases the water status of plants in the dry season. That is, FWU results in a compensation between CO2 assimilation and foliar hydration, which, in fact, is beneficial to the plants of this ecosystem.

Arbuscular mycorrhizal influence on oxidative stress in French bean (Phaseolus vulgaris) under drought conditions

We investigated the antioxidant response in French bean (Phaseolus vulgaris) seedlings in a symbiotic interaction with Arbuscular mycorrhiza fungi (AMF) under drought and studied both shooting and rooting tissues to detect the targeted tissue for AMF effects induced under drought. AMF and Non-AMF French bean seedlings were grown under control (well-watered: WW) and drought-stress (DS) conditions to study their tolerance response by assessing various physiological and biochemical parameters. AMF plants appeared to be sheltered from drought as seen by their higher leaf water potential and production of shoot-biomass. The AMF shoots accumulated less proline than those of non-AMF, while the opposite was observed in roots. Also, in DS AMF plants, lipid peroxides were 60 percent lower than in DS non - AMF plants. However, no significant correlation could be established between antioxidant enzyme activity and the low lipid oxidative damage in AMF plants due to which it appears that the symbiont fungus enhances osmotic adjustment first in the root system, which promotes a water potential gradient that favors entry of water into roots from the soil. This enables increased leaf water potential in DS-AMF plants keeping plants sheltered from oxidative damage, and all these collective effects increase the drought hardiness of seedlings.

Hydraulic redistribution of foliar absorbed water causes turgor-driven growth in mangrove seedlings.

Although foliar water uptake (FWU) has been shown in mature Avicennia marina trees, the importance for its seedlings remains largely unknown. A series of experiments were therefore performed using artificial rainfall events in a greenhouse environment to assess the ecological implications of FWU in A.marina seedlings. One-hour artificial rainfall events resulted in an increased leaf water potential, a reversed sap flow, and a rapid diameter increment signifying a turgor-driven growth of up to 30.1±5.4μm. Furthermore, the application of an artificial rainfall event with deuterated water showed that the amount of water absorbed by the leaves and transported to the stem was directly and univocally correlated to the observed growth spurts. The observations in this process-based study show that FWU is an important water acquisition mechanism under certain circumstances and might be of ecological importance for the establishment of A.marina seedlings. Distribution of mangrove trees might hence be more significantly disturbed by climate change-driven changes in rainfall patterns than previously assumed.

Application of sucrose modulates the expressions of genes involved in proline and polyamine metabolism in maize seedlings exposed to drought

Sucrose, proline, and polyamines are compatible solutes accumulating in plant tissues and increasing cellular osmolarity under environmental stresses. These compatible solutes and hydrogen peroxide can function as signaling molecules in plants. There has been very little evidence how the supply of sucrose changes the biosynthesis of compatible solutes. This study aimed to assess the cross-talk among sucrose, H2O2, and compatible solutes on the expression of genes encoding key enzymes in the pathways of proline and polyamine metabolism in drought stressed maize seedlings. Drought stress (induced by polyethylene glycol solution) increased the expressions of genes encoding pyrroline-5-carboxylate synthetase (P5CS), arginine decarboxylase (ADC), and S-adenosylmethionine decarboxylase (SAMDC), while decreased proline dehydrogenase (ProDH), diamine oxidase (DAO), and polyamine oxidase (PAO) expressions. Addition of sucrose to the stressed seedlings increased the P5CS, ADC and SAMDC expressions more than drought stress alone and reduced more the ProDH, DAO, and PAO expressions. Moreover, exogenous sucrose increased leaf water potential and the content of proline, polyamines, and total soluble sugars, whereas decreased H2O2 content and membrane damages under the drought stress conditions. Consequently, exogenous sucrose contributed to the preservation of water status and the amelioration of damage in maize seedlings under the drought stress.

Exogenous easily extractable glomalin-related soil protein improves drought tolerance of trifoliate orange

ABSTRACTMycorrhiza-released glomalin-related soil protein (GRSP) influences rhizosphere properties, but it is not clear whether exogenous GRSP enhances drought tolerance of plants. In this work, easily extracted GRSP (EE-GRSP) was isolated from Satsuma mandarin soil, and half-strength EE-GRSP (0.007 mg protein mL−1) was weekly applied into rhizosphere of potted trifoliate orange (Poncirus trifoliata) exposed to well watered (WW) and drought stress (DS). After four months, EE-GRSP-treated seedlings exhibited significantly higher plant growth (plant height, leaf number and fresh weight) and root growth-related parameters (lateral root numbers and root morphology) than non-EE-GRSP-treated seedlings under both WW and DS conditions. Exogenous EE-GRSP generally significantly increased leaf water potential, net photosynthesis rate, transpiration rate, stomatal conductance and intercellular CO2 concentration, while dramatically decreased leaf temperature, regardless of soil water status. The seedlings treated with exogenous EE-GRSP observed significantly higher activities of leaf Fe-SOD and root Mn-SOD, Cu/Zn-SOD, and Fe-SOD than untreated control under DS. Leaf abscisic acid, indole-acetic acid and methyl jasmonate concentrations were significantly higher in EE-GRSP-treated seedlings than untreated control under DS. This work firstly reported that exogenous application of EE-GRSP improved drought tolerance of trifoliate orange, thereby, offering a strong possibility in favour of EE-GRSP to be used as a plant growth regulator.

Water Status,Vegetative Growth and Yield Responses of Vitis vinifera L. cvs. Sauvignon blanc and Chenin blanc to Timing of Irrigation during Berry Ripening in the Coastal Region of South Africa

The effects of additional irrigation during berry ripening on water relations, growth and yield in Sauvignon blanc and Chenin blanc grapevines were investigated. In all treatments the grapevines were irrigated when berries reached pea size in December. One treatment received no further irrigation until after harvest. All of the remaining treatments received a second irrigation at veraison. Except for a single treatment, which was not irrigated during ripening, these treatments received a third irrigation at either 14, 21, 28 or 31 days after veraison. The six treatments were applied in a field trial carried out in the Stellenbosch district of the coastal winegrowing region of South Africa over consecutive seasons, between 1990 and 1993. Irrigation at pea size berries and at pea size berries plus veraison increased leaf water potential, but did not affect vegetative growth and yield in either cultivar. Relative to a single application at pea size berries, irrigation at pea size, at veraison and during ripening increased berry size in both cultivars, though not consistently, over the three seasons. However, this result must be viewed in terms of the fact that qualitative assessments of root development and distribution have revealed that effective soil preparation contributes to well-developed root systems. Results confirmed that these root systems could sustain vegetative growth and yield where a single irrigation was applied at pea size berries compared with additional irrigations applied at veraison and during ripening. Irrigation applied at, and after, veraison resulted in yield losses of both cultivars when rainfall favoured Botrytis cinerea infection.

Improvement of grapevine physiology and yield under summer stress by kaolin-foliar application: water relations, photosynthesis and oxidative damage

Knowledge about short-term climate change adaptation strategies for Mediterranean vineyards is needed in order to improve grapevine physiology and yield-quality attributes. We investigated effects of kaolin-particle film suspension on water relations, photosynthesis and oxidative stress of field-grown grapevines in the Douro region (northern Portugal) in 2012 and 2013. Kaolin suspension decreased leaf temperature by 18% and increased leaf water potential (up to 40.7% in 2013). Maximum photochemical quantum efficiency of PSII was higher and the minimal chlorophyll fluorescence was lower in the plants sprayed by kaolin. Two months after application, net photosynthesis and stomatal conductance at midday increased by 58.7 and 28.4%, respectively, in treated plants. In the same period, kaolin treatment increased photochemical reflectance, photosynthetic pigments, soluble proteins, soluble sugars, and starch concentrations, while decreased total phenols and thiobarbituric acid-reactive substances. Kaolin application can be an operational tool to alleviate summer stresses, which ameliorates grapevine physiology and consequently leads to a higher yield.

平潭岛典型海岸草丛沙堆植物群落水势日变化特征及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 平潭岛典型海岸草丛沙堆植物群落水势日变化特征及其影响因素 DOI: 10.5846/stxb201411172277 作者: 作者单位: 中山大学地理科学与规划学院,中山大学地理科学与规划学院,中山大学地理科学与规划学院,中山大学地理科学与规划学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41101011,41371030);中央高校基本科研业务费专项资金(121gpy15) Diurnal variations of water potential and its influencing factors in typical plant communities on coppice dunes of pingtan island Author: Affiliation: School of Geography and Planning,Sun Yat-Sen University,School of Geography and Planning,Sun Yat-Sen University,School of Geography and Planning,Sun Yat-Sen University,School of Geography and Planning,Sun Yat-Sen University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水势是反映植物受到环境胁迫的重要指标之一,可用来确定其受胁迫的程度和适应能力大小。以福建省平潭岛海岸典型沙生植物老鼠艻(Spinifex littoreus)形成的草丛沙堆为研究对象,选取晴朗无云的天气,采用PSYPRO水势测量系统对其植物叶、茎水势及其所形成的沙堆土壤水势进行测定,同时采用HUMIPORT10手持式温湿度计对当日的气象要素进行同步观测。结果表明:(1)老鼠艻的叶水势呈现出与早晚高午间低相反的反梯度现象,叶、茎水势的日变化均表现为"M"型变化趋势,除18:00后,其它时间均表现为叶片水势下降、茎干水势上升,并且发现叶、茎水势的变化趋势存在位相后移现象;(2)老鼠艻的叶、茎水势在10:00时差异达到最大的0.65MPa,且茎水势高于叶水势,在14:00左右,植物茎水势出现低于叶水势的反常现象,在18:00时叶、茎水势趋于相同;(3)除表层30cm外,其它层土壤水势日变化特征总体表现为从早晨开始下降,14:00达到最低,但总体变化不明显;(4)随着深度增加,草丛沙堆土壤水势呈现为依次增加的趋势,但80cm以下土壤水势变化不显著(P > 0.1);(5)叶水势与大气水势具有较好的相关性,且变化显著(P < 0.1),与茎水势及浅层土壤水势有一定相关性,但变化不显著(P > 0.1),与50cm以下土壤水势均无相关性。 Abstract:Water potential is one of the most important factors that reflect environmental stress on plants, and can be used to identify the level of stress a plant experiences and its adaptation ability. This study focused on the coppice dunes formed by the psammophyte Spinifex littoreus on Pingtan Island, Fujian province. The PSYPRO Water Potential System was used to determine the water potential of the leaves, stems, and soil, and a HUMIPORT10 hand-held hygrometer was used to simultaneously measure the meteorological variables on cloudless, sunny days. Spinifex littoreus showed an opposite pattern of leaf water potential, which is in contrast to the normal phenomenon of increased leaf water potential in the morning and evening compared to that at midday. The diurnal variations of leaf and stem water potential all demonstrated an 'M’ curve pattern, indicating a decrease of leaf water potential and increase of stem water potential in daytime, until 18:00. Furthermore, we found that the changes of leaf water potential occurred later than those of stem water potential. The biggest discrepancy between stem and leaf water potential, reaching 0.65MPa, appeared at 10:00, when stem water potential was higher than leaf water potential. At about 14:00, an abnormal phenomenon appeared, in which leaf water potential was higher than stem water potential, but at about 18:00, leaf and stem water potential tended to be the same. With the exception of soil water potential at 30cm, the diurnal variation of soil water potential showed a decrease starting in the morning, which reached the minimum at 14:00; however, this tendency was not statistically significant(P > 0.1). With increasing depth, the soil water potential showed a tendency to increase, but this trend disappeared below a depth of 80cm. Strong correlations and significant changes (P < 0.1) in water potential were observed between the atmosphere water potential and leaf. Leaf, stem, and 30-cm-deep soil water potential showed some correlations, but the variations were not statistically significant (P > 0.1). Leaf water potential was not correlated with the water potential of soil at other depths. 参考文献 相似文献 引证文献

Leaf gas exchanges and water relations affect the daily patterns of fruit growth and vascular flows in Abbé Fétel pear (Pyrus communis L.) trees

Daily patterns of leaf and stem water potentials, leaf gas exchanges (net photosynthesis, stomatal conductance and transpiration), fruit growth, vascular (phloem and xylem) and transpiration in/outflows were determined in two subsequent years at regular time intervals during the season on pear trees of the cv. Abbé Fétel. Leaf gas exchanges showed higher values in the morning, while fruit shrank due to high transpiration water losses which were not balanced by xylem flows. Despite the high rates of transpiration, fruit were fully rehydrated in the afternoon thanks to high xylem flows, while phloem import occurred mostly in the midday hours. During most of the season, fruit growth was sustained above all by the xylem flux which represented upto 85% of fruit total inflows. Later, fruit growth rate decreased while dry matter accumulation increased following a rise in the phloem relative contribution to growth, which reached 50% of fruit total inflows. This is the first report to show how the biophysical mechanism of fruit growth in “Abbé Fétel” pear is based on high water exchanges by xylem and transpiration during most of the season. The simultaneous monitoring of leaf gas exchanges and fruit vascular flows during the day suggests how until about 95 days after full bloom (DAFB), leaves are stronger “sinks” for water in the morning while fruit import water mainly during the afternoon, thanks to the increase in leaf water potential following stomatal closure.

Amelioration of Drought in Sorghum (Sorghum bicolor L.) by Silicon

The purpose of this study was to analyze the effects of silicon (Si) nutrition on sorghum growth under drought. The present study investigated the distribution of Si in plant parts under stress conditions and its effects on physiological and growth traits. The study was conducted during 2 years (2007–2009) at PMAS Arid Agriculture University, Rawalpindi, Pakistan. Polyethylene glycol (PEG) 6000 (–4.0, –6.0, –8.0, and –10.0 Mpa) solution was used to screen drought-tolerant (Johar1) and drought-susceptible (SPV462) sorghum (Sorghum bicolor L.) cultivars, which were replicated three times with Si sources of potassium silicate (K2SiO3) (Si300: 300 ml L−1) and control (Si0) treatments. The results showed that drought-tolerant cultivars accumulated maximum Si under Si treatment versus Si absence, which resulted increased leaf water potential, leaf area index, Soil Plant Analysis Development (SPAD) chlorophyll, net assimilation, and relative growth rate over SPV462. Similarly, Si accumulation in leaves conserved transpiration and leaf water potential, verifying Si nutrition as a defense for plants under drought.