Arbuscular Mycorrhizal Fungi Alter Fractal Dimension Characteristics of Robinia pseudoacacia L. Seedlings Through Regulating Plant Growth,Leaf Water Status,Photosynthesis, and Nutrient Concentration Under Drought Stress

The influence of arbuscular mycorrhizal fungi (AMF), Funneliformis mosseae and Rhizophagus intraradices, on plant growth, leaf water status, chlorophyll concentration, photosynthesis, nutrient concentration, and fractal dimension (FD) characteristics of black locust (Robinia pseudoacacia L.) seedlings was studied in pot culture under well-watered, moderate drought stress, and severe drought stress treatments. Mycorrhizal seedlings had higher dry biomass, leaf relative water content (RWC), and water use efficiency (WUE) compared with non-mycorrhizal seedlings. Under all treatments, AMF colonization notably enhanced net photosynthetic rate, stomatal conductance, and transpiration rate, but decreased intercellular CO₂ concentration. Leaf chlorophyll a and total chlorophyll concentrations were higher in AM seedlings than those in non-AM seedlings although there was no significant difference between AMF species. AMF colonization improved leaf C, N, and P concentrations, but decreased C:N, C:P, and N:P ratios. Mycorrhizal seedlings had a larger FD value than non-mycorrhizal seedlings. The FD value was positively and significantly correlated to the plant growth parameters, photosynthesis, RWC, WUE, and nutrient concentration but negatively correlated to leaf/stem ratio, C:N and C:P ratios, and intercellular CO₂ concentration. We conclude that AMF lead to an improvement of growth performance of black locust seedlings under all growth conditions, including drought stress via improving leaf water status, chlorophyll concentration, photosynthesis, and nutrient uptake. Moreover, FD technology proved to be a powerful non-destructive method to characterize the effect of AMF on the physiology of host plants during drought stress.     

Synergistic effect of colonization with arbuscular mycorrhizal fungi improves growth and drought tolerance of Plukenetia volubilis seedlings

The objective of this study was to investigate the effects of arbuscular mycorrhizal fungus (AMF) inoculation on plant growth and drought tolerance in seedlings of a promising oilseed crop, Sacha Inchi (Plukenetia volubilis L.), under well-watered or drought conditions. AMF inoculation was applied in four treatments: without AMF inoculation, Glomus versiforme, Paraglomus occultum, or combination of both microorganism inoculations. The results showed that AMF colonization significantly enhanced the growth of Sacha Inchi seedlings regardless of soil water conditions, and the greatest development was reached in plants dually inoculated under well-watered conditions. G. versiforme was more efficient than P. occultum. Plants inoculated with both symbionts had significantly greater specific leaf area, leaf area ratio and root volume when compared with the uninoculated control, G. versiforme, and P. occultum treatments alone, indicating a synergistic effect in the two AMF inoculation. Photosynthetic rate and water-use efficiency were stimulated by AMF, but not stomatal conductance. Inoculation with AM fungus increased antioxidant enzymes activities including guaiacol peroxidase and catalase, thus lowering hydrogen peroxide accumulation and oxidative damage, especially under drought stress conditions. However, proline content showed little change during drought stress and AMF colonization conditions, which suggested that proline accumulation might not serve as the main compound for osmotic adjustment of the studied species. These results indicate that AMF inoculation stimulated growth and enhanced drought tolerance of Sacha Inchi seedlings, through alterations in morphological, physiological and biochemical traits. This microbial symbiosis might be an effective cultivation practice in improving the performance and development for Sacha Inchi plants.     

Arbuscular mycorrhizal fungi influence growth, osmotic adjustment and photosynthesis of citrus under well-watered and water stress conditions

The influence of arbuscular mycorrhizal (AM) fungus Glomus versiforme on plant growth, osmotic adjustment and photosynthesis of tangerine (Citrus tangerine) were studied in potted culture under well-watered and water stress conditions. Seven-day-old seedlings of tangerine were transferred to pots containing Glomus versiforme or non-AMF. After 97 days, half of the seedlings were subject to water stress and the rest were well-watered for 80 days. AM colonization significantly stimulated plant growth and biomass regardless of water status. The soluble sugar of leaves and roots, the soluble starch of leaves, the total non-structural carbohydrates (NSC) of leaves and roots, and the Mg(2+) of leaves were higher in AM seedlings than those in corresponding non-AM seedlings. The levels of K(+) and Ca(2+) in leaves and roots were higher in AM seedlings than those in non-AM seedlings, but differences were only significant under water stress conditions. Moreover, AM colonization increased the distributed proportions of soluble sugar and NSC to roots. However, the proline was lower in AM seedlings compared with that in non-AM seedlings. AM seedlings had higher leaf water potential (Psi), transpiration rates (E), photosynthetic rates (Pn), stomatal conductance (g(s)), relative water content (RWC), and lower leaf temperature (Lt) than corresponding non-AM seedlings. This research also suggested that AM colonization improved the osmotic adjustment originating not from proline but from NSC, K(+), Ca(2+) and Mg(2+), resulting in the enhancement of drought tolerance.     

正常和环割条件下不同形态氮素添加对红椎幼苗光合特性的影响

采用盆栽试验和韧皮部环割方法研究了碳水化合物供应、氮素形态及其交互作用对红椎幼苗叶片光合特性的影响。无机氮源采用硝酸铵(AN)、铵态氮(NH_4~+-N)、硝态氮(NO_3~--N),有机氮源采用尿素(Urea)、精氨酸(Arg)和甘氨酸(Gly),氮素施用量均为10g N/m~2,处理时间为10 d。研究结果表明,环割、氮素形态及其交互作用均显著影响了红椎幼苗叶片的净光合速率(Pn);单一环割处理显著降低了红椎幼苗叶片Pn、气孔导度(Gs)、胞间CO_2浓度(Ci)、蒸腾速率(Tr)、相对叶绿素含量和CO2利用效率(CUE),但显著提高了叶片水分利用效率(WUE)和气孔限制值(Ls),其叶片Pn降低主要是由气孔限制和叶绿素含量降低所导致的。正常条件下,所有氮素形态处理均显著降低了红椎幼苗叶片的Pn、Gs、Ci和Tr,但显著升高了叶片Ls和WUE,其叶片Pn降低的主要原因是供氮过高引起的叶片气孔限制。正常条件下,除Arg处理外,其他氮素形态均显著升高了红椎幼苗叶片的CUE,其中以Gly处理的促进作用最大。环割条件下,3种有机态氮素的添加均显著缓解了单一环割处理对红椎幼苗叶片Pn的抑制作用,尤其以精氨酸最为明显,供应精氨酸的叶片Pn值从单一环割处理的强烈抑制中恢复到了对照水平,而无机态氮的供应均未显著改变这种抑制。结果表明短期碳水化合物供应的阻断会显著抑制红椎幼苗叶片的光合能力,适量供应精氨酸、甘氨酸和尿素等有机态氮会有效缓解这种抑制作用,其中以精氨酸的作用最为明显。     

Compensatory photosynthesis as a response to partial debudding in ezo spruce, <Emphasis Type="Italic">Picea jezoensis</Emphasis> seedlings

The effects of partial debudding on photosynthesis, stomatal conductance and nitrogen contents of 1-year-old needles and newly grown needles were studied in Picea jezoensis (Sieb. et Zucc.). Seventy-five percent of the buds of P.jezoensis seedlings were removed soon after bud break. Gas exchange was measured three times for 1-year-old needles and twice for current-year needles. The photosynthetic rates of 1-year-old needles were greater in debudded seedlings than in control seedlings, and the difference increased as the growing season progressed. This greater photosynthetic rate in debudded seedlings was accompanied by greater stomatal conductance. However, neither the photosynthetic rates nor the stomatal conductance of current-year needles differed between debudded and control seedlings after the needles had fully expanded. Debudding also had no effect on mass-based nitrogen contents in either the 1-year-old or the current-year needles. Area-based nitrogen in the 1-year-old needles did not differ between debudded and control seedlings, but was greater in debudded seedlings than in control seedlings in current-year needles. These results suggest that the enhanced photosynthetic rate is more likely a result of an increased root/leaf ratio that reduces the stomatal limitation of photosynthetic rate than a result of altered sink-source relationships or increased leaf nitrogen content.     

Field response of wheat to arbuscular mycorrhizal fungi and drought stress

Mycorrhizal plants often have greater tolerance to drought than nonmycorrhizal plants. This study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi inoculation on growth, grain yield and mineral acquisition of two winter wheat (Triticum aestivum L.) cultivars grown in the field under well-watered and water-stressed conditions. Wheat seeds were planted in furrows after treatment with or without the AM fungi Glomus mosseae or G. etunicatum. Roots were sampled at four growth stages (leaf, tillering, heading and grain-filling) to quantify AM fungi. There was negligible AM fungi colonization during winter months following seeding (leaf sampling in February), when soil temperature was low. During the spring, AM fungi colonization increased gradually. Mycorrhizal colonization was higher in well-watered plants colonized with AM fungi isolates than water-stressed plants. Plants inoculated with G. etunicatum generally had higher colonization than plants colonized with G. mosseae under both soil moisture conditions. Biomass and grain yields were higher in mycorrhizal than nonmycorrhizal plots irrespective of soil moisture, and G. etunicatum inoculated plants generally had higher biomass and grain yields than those colonized by G. mosseae under either soil moisture condition. The mycorrhizal plants had higher shoot P and Fe concentrations than nonmycorrhizal plants at all samplings regardless of soil moisture conditions. The improved growth, yield and nutrient uptake in wheat plants reported here demonstrate the potential of mycorrhizal inoculation to reduce the effects of drought stress on wheat grown under field conditions in semiarid areas of the world.     

Effects of drought stress on photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean plants

Changes in plant growth, photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean [Glycine max (L.) Merr.] plants under drought stress were studied. Total plant dry mass was reduced by 30 % compared to well-watered control plants. Leaf water potential was slightly decreased by water stress. Water stress induced daytime shrinkage and reduced night-time expansion of stem. Photosynthetic rate, stomatal conductance and transpiration rate were significantly declined by water stress, while the intercellular CO₂ concentration was changed only slightly at the initiation of stress treatment. The maximum photochemical efficiency of photosystem 2 and apparent photosynthetic electron transport rate were not changed by water stress.     

水分胁迫下AM真菌对枳实生苗叶片矿质营养吸收的影响

在温室盆栽条件下研究丛枝菌根真菌(AM真菌)Glomus versiforme对水分胁迫下(正常水分为对照)的枳[Poncirus trifoliata (L.) Raf.]实生苗叶片矿质营养吸收的影响.研究表明,水分胁迫显著抑制AM真菌对枳实生苗根系的侵染.无论在正常水分还是在水分胁迫下,AM真菌的感染显著提高枳实生苗叶片P、K和Ca的含量,水分胁迫下的菌根贡献率均高于对照;AM真菌的接种对叶片N、Mg和Cu含量没有显著影响.与未接种处理相比,AM真菌处理仅对水分胁迫下的枳实生苗叶片Fe和Zn含量有显著促进作用.研究还表明,接种处理降低叶片Mn含量,正常水分下达到显著水平.     

Stomatal and nonstomatal limitations to net photosynthesis in seedlings of woody angiosperms

Comparative responses of net photosynthesis (A) to water stress in woody species from a variety of habitats were studied to assess the relationship between photosynthetic attributes and drought tolerance. Stomatal and nonstomatal limitations to A were compared in three-month-old white oak (Quercus alba L.), post oak (Quercus stellata Wangenh.), sugar maple (Acer saccharum Marsh.), and black walnut (Juglans nigra L.) seedlings during a drying cycle. Relative stomatal limitation of photosynthesis (I) was less than 50% in all species except for Q. stellata seedlings subjected to severe water stress. No significant changes in I were observed in Q. alba and J. nigra before, during, and after drought. In A. saccharum, I was generally low and decreased significantly under water stress. Under well-watered conditions, A was highest in Q. stellata, intermediate in Q. alba, and lower in A. saccharum and J. nigra. High A in well-watered Q. stellata was associated with high stomatal conductance and carboxylation efficiency, whereas low A was associated with low stomatal conductance and carboxylation efficiency in A. saccharum and low stomatal conductance, low carboxylation efficiency, and high CO₂ compensation point in J. nigra. Under severe water stress, A, carboxylation efficiency, and stomatal conductance decreased substantially in all species; however, Q. stellata had the highest carboxylation efficiency and lowest CO₂ compensation point under these conditions. After 5 days at high soil moisture after drought, stomatal and mesophyll components of A in A. saccharum and J. nigra had not recovered to predrought levels, whereas they had completely recovered in Q. stellata and Q. alba. The photosynthetic apparatus, especially mesophyll components, of drought-tolerant Quercus species showed either less inhibition under water stress, superior recovery to predrought capacity, or both. Exposure of the leaves to ¹⁴CO₂ indicated apparent asymmetric stomatal closure for mildly water-stressed seedlings, but not for leaves of well-watered, severely stressed, or rehydrated plants. These results suggest that patchy stomatal closure under mild water stress might be important for water stress-induced inhibition of photosynthesis, but not under the more severe water stress imposed in this study.     

Evaluation of mycelial inocula of edible<Emphasis Type="Italic"> Lactarius</Emphasis> species for the production of<Emphasis Type="Italic"> Pinus pinaster</Emphasis> and<Emphasis Type="Italic"> P. sylvestris</Emphasis> mycorrhizal seedlings under greenhouse conditions

Different methods to inoculate seedlings of Pinus pinaster and P. sylvestris with edible Lactarius species under standard greenhouse conditions were evaluated. Fungal inoculations were performed both under pure culture synthesis in vitro, followed by transplantation of acclimatized seedlings, and directly in the greenhouse using different techniques for inocula production (mycelial slurries, vegetative inoculum grown in peat-vermiculite and alginate-entrapped mycelium). In vitro inoculations with L. deliciosus produced thoroughly colonized seedlings. However, a sharp decrease in mycorrhizal colonization was detected on transplanted seedlings after 4 month's growth in the greenhouse. On the other hand, all the inocula applied directly in the greenhouse, except the alginate-entrapped mycelium, produced a variable number of mycorrhizal seedlings and colonization rates after the first growing season, depending on the plant-fungal combination and the inoculation method. Inoculations with vegetative inocula of the strain 178 of L. deliciosus were the most effective in producing mycorrhizal seedlings. All the seedlings inoculated with this strain were colonized although the colonization rates were relatively low. The commercial feasibility of the different inoculation methods for the production of seedlings colonized with edible Lactarius species is discussed.     

Effects of zinc and soil moisture on photosynthetic rate and chlorophyll fluorescence parameters of maize

Effects of zinc [0 and 5.0 mg Zn kg⁻¹ (soil)] on photosynthetic rate (P_N), and chlorophyll fluorescence in leaves of maize (Zea mays L.) cv. Zhongdan 9409 seedlings grown under different soil moisture regimes (40–45 % and 70–75 % of soil saturated water content) were studied. Zn application did not enhance maize plant adaptation to drought stress. The relative water content and the water potential of leaves were not affected by Zn treatment. Moreover, The P_N of drought-stressed plants was not improved by Zn supply. The increases of plant biomass, stomatal conductance and quantum yield of photosystem 2 due to Zn addition were notable in well-watered plants.     

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.     

Effect of phosphorus fertilization on water stress in Douglas fir seedlings during soil drying

A growth chamber experiment was conducted to determine if P fertilization to enhance the P nutrition of otherwise N and P deficient Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings reduces water stress in the seedlings during drought periods. Seedlings were grown in pasteurized mineral soil under well-watered conditions and fertilized periodically with a small amount of nutrient solution containing P at either of three levels: 0, 20, or 50 mg P L^-1. By age 6 mo, leaf nutrient analysis indicated that N and P were deficient in control (0 mg P L^-1) seedlings. The highest level of P fertilization, which doubled leaf P concentration, did not affect plant biomass, suggesting that N deficiency was limiting growth. When these seedlings were subjected to drought, there was no effect of P fertilization on leaf water potential or osmotic potential. Furthermore, P fertilized seedlings had lower stomatal conductance and net photosynthesis rate. These results indicate that enhanced P nutrition, in the presence of N deficiency, does not reduce water stress in Douglas fir seedlings during drought periods.     

Ectomycorrhizal and arbuscular mycorrhizal colonization of two species of floodplain willows

To understand the relationships between the distribution of Chosenia arbutifolia and Salix sachalinensis and their mycorrhizal colonization, changes in the quality and types of ectomycorrhizas and arbuscular mycorrhizas of the seedlings of two species were studied at five different sites with different soil conditions in the floodplain of the Satsunai River, Hokkaido. High ectomycorrhizal and low arbuscular mycorrhizal colonization were found in roots of both plants. Ectomycorrhizal colonization of S. sachalinensis in wet sandy or muddy soil conditions was at the same level as that in dry gravelly sites. In contrast, ectomycorrhizal colonization of C. arbutifolia seedlings was lower from wet sandy sites than that from dry gravelly sites. In all study sites, the same three morphological types of ectomycorrhizas were dominant.     

Differential response of leaf gas exchange to enhanced ultraviolet-B (UV-B) radiation in three species of herbaceous climbingplants

We measured diurnal changes in photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency in three species of herbaceous climbing plants (Luffa cylindrica, Trichosanthes kirilowii and Dioscorea opposita) exposed to two intensities of UV-B radiation: 3.0 μw cm^?2 (R1) and 8.0 μw cm^?2 UV-B (R2) radiation under ambient growth conditions. Responses differed per species and per treatment. In Luffa all values increased compared to the Control in both treatments, except for stomatal conductance in R2. In Trichosanthes photosynthetic rates and water use efficiency increased, while the transpiration rates decreased under both treatments, and stomatal conductance was lower in R1. In Dioscorea photosynthetic rates and water use efficiency decreased under both treatments, while the transpiration rates and stomatal conductance increased. The results suggested that to some extent increased UV-B radiation was beneficial to the growth of L. cylindrica and T. kirilowii, but detrimental to D. opposita.     

Growth and gas exchange responses of Hevea brasiliensis seedlings to inoculation with Glomus mosseae

 The beneficial effect of arbuscular mycorrhizal (AM) fungi on plant growth is well known, but the physiological processes involved are still discussed. The purpose of this study was to determine if Glomus mosseae affects the growth of Hevea brasiliensis seedlings and, if it is the case, if it could be associated with variations in leaf CO₂ and H₂O gas exchange. H. brasiliensis rubber trees were grown for 9 months in a medium containing either propagules of G. mosseae or sterilized inoculum. Plant size, root collar diameter and leaf area, as well as net CO₂ assimilation, stomatal conductance (g_s) and water-use efficiency of photosynthesis were evaluated during the first 5 stages of growth. At stage 2, a growth depression occurred in the mycorrhizal seedlings coincident with the first AM infections. Then, at stage 5, Glomus mosseae-inoculated plants had moderate colonization (47% of root length) and were taller than control plants with a larger root collar diameter and an enhanced leaf organogenesis. This enhanced growth was accompanied by increased photosynthesis, transpiration, and stomatal conductance. After 9 months, dry weights of shoots and roots of inoculated plants were greater than those of controls by 27 and 17%, respectively. Received: 10 May 1997 / Accepted: 9 September 1997     

干旱胁迫对降香黄檀幼苗光合生理特性的影响

采用温室盆栽方法,设置对照(CK)、轻度(LS)、中度(MS)和重度(HS)干旱胁迫4个水分条件,研究不同水分条件对降香黄檀幼苗光合和生理特性的影响。结果表明:(1)随着干旱胁迫程度增加,降香黄檀幼苗叶片叶绿素总含量总体呈现出下降趋势。(2)降香黄檀幼苗叶片净光合速率、气孔导度、胞间CO2浓度和蒸腾速率随着干旱胁迫强度增加均呈现出先增加后降低趋势,且MS和HS处理下的气孔导度和胞间CO2浓度同时降低,此时幼苗光合能力的下降主要受气孔因素限制。(3)随着干旱胁迫强度的增加,降香黄檀幼苗叶片细胞膜相对透性、丙二醛含量、游离脯氨酸含量和POD活性均呈现出增加趋势,而同期SOD和CAT活性呈现出先升高后降低趋势。可见,降香黄檀幼苗在轻度干旱胁迫下可通过增加叶片保护酶活性来清除活性氧对其组织造成的伤害,但胁迫超过一定程度后保护酶活性下降,表明降香黄檀幼苗的耐旱能力有限。     

The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit

We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO₂ transporter, as well as control the regulation of stomata to water deficits.     

Response ofBromus inermis inoculated withGlomus fasciculatum to potassium fertilization and drought stress

Summary Bromus inermis Leyss. was grown in a 2×2×2 factorial design using different levels of mycorrhizal inoculation (inoculated and noninoculated), soil water stress (Ψ₁ or −0.8 MPa) and potassium (K) fertilization (0 or 150 ppm) as factors. Soil water stress and mycorrhizal inoculation significantly reduced plant top dry weight during the 18 week study. Chlamydospore production by the mycorrhizal symbiontGlomus fasciculatum (Thaxter sensu. Gerd.) Gerd. and Trappe was significantly reduced by soil water stress of −0.8 MPa. Potassium (K) fertilization did not significantly influence plant top growth or mycorrhizal colonization. However, foliar Ca and Mg were significantly lower in plants fertilized with K. Foliar Ca and Mg concentrations of P, K, N, Mn, Zn and Cu were significantly greater in drought stressed plants whereas Ca and Mg concentrations were significantly greater in well-watered plants.     

The influence of plant water stress on stomatal control of gas exchange at different levels of atmospheric humidity

Summary Leaves of well-watered and mildly water-stressed seedlings of Betula pendula Roth. and Gmelina aroborea L. were subjected to a range of vapour pressure deficits (VPD) between 10 and 24 kPa. The stomatal conductance of birch seedlings decreased as VPD was increased and at least in mildly-stressed seedlings this response seemed to be closely linked to the water status of the air rather than to the bulk water status of the plant. Mild water stressing enhanced the degree of the stomatal humidity-response and resulted in a significant increase in the efficiency of water use at high VPD. Stomata of Gmelina were apparently insensitive to variation in VPD, but were more sensitive to a decrease in bulk leaf water status than were stomata of birch. Water use efficiency of Gmelina seedlings was comparatively high, even when VPD was high and the stomata were fully open.