Soluble Sugar Contents In Roots Research Articles

Bacillus megaterium Compensates for Growth Inhibition from Phosphorus Deficiency by Improving Photosynthetic Capacity, Changing Antioxidant Potential, and Regulating Non-Structural Carbohydrate Concentrations in Glycyrrhiza uralensis

This study assessed the effect of Bacillus megaterium on seedling growth of Glycyrrhiza uralensis Fisch. under control and phosphorus (P) deficiency conditions. The results showed that P deficiency improved 1) G. uralensis root growth, 2) superoxide dismutase, catalase, and peroxidase activities, 3) inorganic P, starch, and soluble sugar contents in roots, 4) dissipated energy flux per reaction center, trapped energy flux per reaction center, and absorption flux per reaction center, and 5) net photosynthetic rate, stomatal conductance, transpiration rate, maximum fluorescence intensity after dark adaptation, and variable fluorescence. However, P deficiency significantly decreased chlorophyll and carotenoid contents in G. uralensis, but enhanced chlorophyll and carotenoid contents in B. megaterium. Our findings on the regulatory mechanisms of B. megaterium in response to P starvation hold promise for improving the success of G. uralensis cultivation.
 Keywords: Bacillus megaterium; Glycyrrhiza uralensis Fisch; Phosphorus deficiency; Chlorophyll fluorescence; Antioxidant enzymes superoxide; Non-structural carbohydrate

Precipitation pattern changed the content of non-structural carbohydrates components in different organs of Artemisia ordosica

BackgroundNon-structural carbohydrates (NSC) play a significant role in plant growth and defense and are an important component of carbon cycling in desert ecosystems. However, regarding global change scenarios, it remains unclear how NSCs in desert plants respond to changing precipitation patterns. [Methods] Three precipitation levels (natural precipitation, a 30% reduction in precipitation, and a 30% increase in precipitation) and two precipitation intervals levels (5 and 15 d) were simulated to study NSC (soluble sugar and starch) responses in the dominant shrub Artemisia ordosica.ResultsPrecipitation level and interval interact to affect the NSC (both soluble sugar and starch components) content of A. ordosica. The effect of precipitation on NSC content and its components depended on extended precipitation interval. With lower precipitation and extended interval, soluble sugar content in roots increased and starch content decreased, indicating that A. ordosica adapts to external environmental changes by hydrolyzing root starch into soluble sugars. At 5 d interval, lower precipitation increased the NSC content of stems and especially roots.ConclusionsA. ordosica follows the “preferential allocation principle” to preferentially transport NSC to growing organs, which is an adaptive strategy to maintain a healthy physiological metabolism under drought conditions. The findings help understand the adaptation and survival mechanisms of desert vegetation under the changing precipitation patterns and are important in exploring the impact of carbon cycling in desert systems under global environmental change.

Contrasting effect of irrigation practices on the cotton rhizosphere microbiota and soil functionality in fields.

Drip irrigation under plastic film mulch is a common agricultural practice used to conserve water. However, compared to traditional flood irrigation with film mulch, this practice limit cotton root development from early flowering stage and may cause premature senescence in cotton. Changes of root will consequently shape the composition and activity of rhizosphere microbial communities, however, the effect of this farming practice on cotton rhizosphere microbiota remains poorly understood. This study investigated rhizosphere bacteria and soil functionality in response to different irrigation practices -including how changes in rhizosphere bacterial diversity alter soil nutrient cycling. Drip irrigation under plastic film mulch was shown to enhance bacterial diversity by lowering the salinity and increasing the soil moisture. However, the reduced root biomass and soluble sugar content of roots decreased potential copiotrophic taxa, such as Bacteroidetes, Firmicutes, and Gamma-proteobacteria, and increased potential oligotrophic taxa, such as Actinobacteria, Acidobacteria, and Armatimonadetes. A core network module was strongly correlated with the functional potential of soil. This module not only contained most of the keystone taxa but also comprised taxa belonging to Planctomycetaceae, Gemmatimonadaceae, Nitrosomonadaceae, and Rhodospirillaceae that were positively associated with functional genes involved in nutrient cycling. Drip irrigation significantly decreased the richness of the core module and reduced the functional potential of soil in the rhizosphere. Overall, this study provides evidence that drip irrigation under plastic film mulch alters the core bacterial network module and suppresses soil nutrient cycling.

Effects of arbuscular mycorrhizal fungi inoculation on non-structural carbohydrate contents and C:N:P stoichiometry of Heptacodium miconioides under drought stress

A pot experiment was conducted to investigate the effects of drought stress and arbuscular mycorrhizal fungi (AMF) inoculation on C:N:P stoichiometry and non-structural carbohydrate (NSC) contents in two-year-old Heptacodium miconioides seedlings. There were four treatments, including control (CK), drought stress (D), AMF inoculation (AMF), and combined drought stress and AMF inoculation (D+AMF). The results showed that drought stress significantly reduced AMF colonization rate, whereas plant height and leaf number of inoculated treatment were significantly higher than the non-inoculated treatment. Inoculation with AMF significantly increased soluble sugar and NSC content in root and leaf, as well as starch content in stem and leaf. The inoculation significantly decreased the stem and leaf soluble sugar to starch ratio under drought stress. Drought stress caused a significant increase in C content in roots and leaves, and a significant decrease in P content in stems. Compared with no inoculation drought stress, P content in roots, stems, leaves, and C content in leaves of mycorrhizal seedlings were significantly increased by inoculation under drought stress, whereas root C and N content and stem C content were significantly reduced. Under drought stress, AMF inoculation significantly decreased C:N, C:P, and N:P ratios in roots and stems, and N:P ratios in leaves of H. miconioides. P content in roots and leaves were significantly positively correlated with soluble sugar and NSC content. Stem P content was significantly positively correlated with starch and NSC content. N:P ratios in each organ was significantly negatively correlated with NSC content. In all, inoculation with AMF can improve the drought tolerance of H. miconioides seedling by increasing soluble sugar content in roots and leaves and the soluble sugar/starch ratio in roots, improving starch content in above-ground organs, promoting the P absorption, and reducing N:P ratios in each organ. Therefore, AMF colonization could improve the survival rate of H. miconioides seedling in dry environments.

Changes of non-structural carbohydrates in Caryopteris mongolica seedlings during the process of drought-induced mortality

The changes and distribution of non-structural carbohydrate (NSC, including soluble sugar and starch) content in different organs of one-year-old Caryopteris mongolica seedlings were investigated under suitable water condition (CK), slow-dying drought stress, and fast-dying drought stress. There was no significant difference in soluble sugar content of all organs between slow-dying drought stress and CK. With the extended duration of drought, the soluble sugar content in stem increased firstly and then decreased, while starch and NSC contents decreased. The soluble sugar content in coarse roots decreased, while starch and NSC contents increased. The soluble sugar content in leaves increased, while starch and NSC contents of leaves decreased. The NSC content of leaves, stems, coarse roots and fine roots were 6.2%, 7.8%, 8.3% and 7.4% at the death time (80 days), respectively. Under fast-dying drought stress, soluble sugar content in all organs was higher than that in CK, while starch and NSC contents were lower than that in CK. With the increasing time, soluble sugar content of roots decreased, while starch and NSC contents increased. The soluble sugar, starch and NSC contents in stems increased. The soluble sugar content of leaves increased, while starch and NSC contents decreased. The NSC content of leaves, stems, coarse roots and fine roots were 5.9%, 6.6%, 8.9% and 7.7% at lethal time (30 days), respectively. Under different drought stress, non-structural carbohydrates among different organs of C. mongolica seedlings showed different dynamics. Under slow-dying drought stress, NSC gave priority to allocate energy for maintaining physiological metabolism of organs. Under fast-dying drought stress, NSC mainly maintained plant metabolism in the form of soluble sugar, regulated osmotic potential, promoted water absorption, and coped with drastic drought stress.

Effects of Abscisic Acid on Soluble Sugar Accumulation of Cyphomandra betacea Seedlings under Cadmium Stress

In this study, the effects of different concentrations (0, 1, 5, 10, and 20 μmol/L) of abscisic acid (ABA) on soluble sugar accumulation in Cyphomandra betacea seedlings under cadmium stress were studied. The results showed that spraying 10 and 20 μmol/L ABA could effectively increase the content of soluble sugar in roots, stems, leaves and aerial parts of C. betacea seedlings. Spraying 1 and 5 μmol/L ABA reduced the soluble sugar content in roots, stems, leaves and aerial parts of C. betacea seedlings. Therefore, the use of 20 μmol/L ABA can increase the accumulation of soluble sugar in C. betacea seedlings.

The Potassium Transporter SlHAK10 Is Involved in Mycorrhizal Potassium Uptake.

Most terrestrial plants form a root symbiosis with arbuscular mycorrhizal (AM) fungi, which receive fixed carbon from the plant and enhance the plant's uptake of mineral nutrients. AM symbiosis improves the phosphorous and nitrogen nutrition of host plants; however, little is known about the role of AM symbiosis in potassium (K+) nutrition. Here, we report that inoculation with the AM fungus Rhizophagus irregularis improved tomato (Solanum lycopersicum) plant growth and K+ acquisition and that K+ deficiency has a negative effect on root growth and AM colonization. Based on its homology to a Lotus japonicus AM-induced K+ transporter, we identified a mycorrhiza-specific tomato K+ transporter, SlHAK10 (Solanum lycopersicum High-affinity Potassium Transporter10), that was exclusively expressed in arbuscule-containing cells. SlHAK10 could restore a yeast K+ uptake-defective mutant in the low-affinity concentration range. Loss of function of SlHAK10 led to a significant decrease in mycorrhizal K+ uptake and AM colonization rate under low-K+ conditions but did not affect arbuscule development. Overexpressing SlHAK10 from the constitutive cauliflower mosaic virus 35S promoter or the AM-specific Solanum melongena Phosphate Transporter4 not only improved plant growth and K+ uptake but also increased AM colonization efficiency and soluble sugar content in roots supplied with low K+ Our results indicate that tomato plants have a SlHAK10-mediated mycorrhizal K+ uptake pathway and that improved plant K+ nutrition could increase carbohydrate accumulation in roots, which facilitates AM fungal colonization.

Effects of Chitosan on Soluble Sugar Content in Prunus davidiana Seedlings

A pot experiment was conducted to study the effects of different concentrations of chitosan solutions (0, 1, 2, 4, 6 g/L) on soluble sugar content in Prunus davidiana seedlings. The result showed that there was no significant difference of the soluble sugar content in roots, stems, leaves and shoot in P. davidiana seedlings between at 1 g/L concentration and the control. All concentration treatments were reduced the soluble sugar content in roots and stems of P. davidiana seedlings compared with the control. On the contrary, all concentration treatments were improved the soluble sugar content in leaves and shoot of P. davidiana seedlings compared with the control and the concentration treatment of 2 g/L and 4 g/L was at a higher level. All concentration treatments were improved the content in relative conductivity of blade in P. davidiana seedlings and the concentration treatment of 4 g/L was at a higher level. On the contrary, all concentration treatments were reduced the content in soil conductivity. Therefore, the chitosan solutions concentration of 2 g/L and 4 g/L concentration was beneficial to soluble sugar content in P. davidiana seedlings. On the contrary, high concentration of chitosan solutions was not good for soluble sugar content.

Effects of Biochar on Soluble Sugar Content in Peach Seedlings

A pot experiment was conducted to study the effects of different biochar types [addition of rape straw biochar (RB), addition of paddy straw biochar (PB), addition of wheat straw biochar (WB) and addition of corn straw biochar (MB)] on the soluble sugar content and plant height of peach seedlings. The result showed that the soluble sugar content in roots and leaves of peach seedlings treated with biochar was lower than the control. However, the soluble sugar content in stems was higher than control compared with the control. In the soluble sugar content in the aboveground part, there was no significant difference between the treatment of adding biochar and the control except for the treatment of PB. All the treatment of adding biochar increased the plant height of peach seedlings except the treatment of MB than the control and the treatment of RB and PB were at a higher level. Compared to control, all biochar addition treatments increased stem diameter of peach seedlings and the treatment of RB and PB were at a higher level. Therefore, the treatment of RB and PB was beneficial to the growth of peach seedlings.

Physiological effects of cadmium stress on Astragalus membranaceus seedlings and alleviative effects of attapulgite clay on cadmium stress

In this study we investigate the effects of cadmium stress on Astragalus membranaceus seedlings and the alleviative effects of attapulgite clay in growth substrate on cadmium stress to A. membranaceus seedlings. The results showed that the Y (Ⅱ) (effective photochemical quantum yield of PSⅡ photosynthetic), qP(photochemical quenching coefficient), ETR(the rate of non-cyclic electrontransport through PSⅡ), and chlorophyll content of the leaves were significantly decreased with the increase of cadmium concentrations, while the cadmium content, non-photochemical quenching(NPQ, qN) of the leaves and cadmium content, MDA content, plasma membrane permeability, and the damage degree of root apical membrane of the roots were significantly increased. Simultaneously, the activities of APX(ascorbate peroxidase), SOD(superoxide dismutase), POD(peroxidase), CAT(catalase), soluble protein content, and soluble sugar content of roots were increased first but then decreased with the increasing cadmium concentration. Under the condition of without Cd stress, the attapulgite clay into the growth substrate did not significantly affect above physiological indexes of leaves, but significantly increased SOD activity and soluble sugar content of roots and decreased the MDA content, damage degree of root apical membrane of roots, while other physiological indexes did not significantly change. Under cadmium stress, the presence of attapulgite clay in the growth substrate significantly alleviated the cadmium-induced decreases Y (Ⅱ), qP, ETR and chlorophyll content of leaves, and the CAT activity, soluble protein content, and soluble sugar content of roots. Under condition with cadmium stress, the presence of attapulgite clay significantly alleviated the cadmium-induced increases of leaves cadmium content, qN and NPQ, and the cadmium content, MDA content, plasma membrane permeability, damage degree of root apical membrane, SOD, POD, and APX activity of the roots. And, the alleviative effects of attapulgite clay on cadmium stress to A. membranaceus roots were more obvious with the increase of cadmium stress time. The above results showed that the addition of attapulgite clay into the growth substrate has certain alleviative effect on the cadmium stress to A. membranaceus seedlings.

Induction of osmotic stress resistance by seed osmo-priming in winter wheat (Triticum aestivum L.) during post-germinative stages

The potential of wheat (Triticum aestivum) seed osmo-priming for post-germinative osmo-stress resistance was evaluated. Further, for comparative evaluation of seed osmo-priming and plant stress-acclimation, a set of plants was stress-acclimated prior to osmo-stress treatment. Under osmo-stress at the post-germination stage, plants from osmo-primed seeds produced 2.3% higher root biomass, 21.6% longer roots, accumulated 15.1% higher soluble sugar content and respectively, 10.4 and 12.8% higher activity of SOD and POD in the roots compared with plants from unprimed seeds. At the post-seedling establishment stage, seed-osmo-primed plants produced 29.9% higher root biomass, 15.2% longer roots, accumulated 32.7% higher soluble sugar content and 31.2% higher proline content in the roots, while the activity of SOD and POD was respectively, 19.6 and 13.1% higher than the unprimed plants. Plant stress-acclimation induced osmo-stress tolerance was exemplified by 6.9% higher root biomass, 4.6% longer roots, 52.7% higher soluble sugar content in roots, 23.9% higher proline content in the roots and 27.0% higher activity of SOD in the roots under osmo-stress when compared with the unprimed plants. The data of seedling morphology and physiological activity under control conditions showed adverse effects of stress acclimation whereas seed osmo-priming-induced stress resistance resulted in advanced germination and higher osmolyte accumulation.

Enhanced photosynthetic capacity by perennials in the riparian zone of the Three Gorges Reservoir Area, China

The flood-dry-flood cycle in the reservoir riparian zone (RRZ) of the Three Gorges Dam has dramatically changed the ecosystem structure and riparian vegetation. Previous field investigations have shown that perennial herbaceous species are dominant in the riparian zone. However, how perennials respond to flooding disturbance remains largely unclear. Intermediate disturbance (e.g. grazing, insect pest) can enhance photosynthesis via “physiological compensation” mechanism. The aim of this study is to investigate whether perennials enhance their photosynthetic capacity during dry periods and understand the mechanisms driving this. Eight species from different families in a RRZ site and a paired Upland site were chosen. We compared 12 plant traits including photosynthesis, leaf structure and nutrients, as well as soluble sugar (indicate sink–source relationship) between the two sites. Results showed that perennials in RRZ had a significant higher area-based photosynthetic capacity (Aarea) than those in Upland. Meanwhile, stomatal conductance (Gs), leaf nitrogen concentration (LNCa) and Stem mass ratio (SMR) were also significantly higher in RRZ than Upland individuals. However, there was no sign of an unbalanced sink–source relationship in RRZ as evidenced by no difference in soluble sugar content in roots and stems between sites. The results of this study suggest that perennials have enhanced photosynthetic capacity in RRZ mainly attributed to higher LNCa and Gs but sink strength was not enhanced. These data provide insight into the ecosystem functioning of riparian areas and could be used to improve restoration practices.

Effect of an IAA overproducer mutant of the fungus hebeloma Cylindrosporum romagnesi on the early stages of ectomycorrhizal infection and carbohydrate content in seedlings of Pinus pinaster (ait.) SOL.

Ectomycorrhizal and control seedlings of <i>Pinus pinaster</i> were cultured on a synthetic Melin-Norkrans medium in Petri dishes. Seedlings were inoculated with a mycelial slurry of an indole-3-acetic acid (IAA) overproducer <i>Hebeloma cylindrosporum</i> mutant 331. The wild strain <i>H. cylindrosporum</i> hl was used as a reference. Medium was supplemented or not with glucose. The mycelial slurry appeared to be very effective for mycorrhizal inoculation even on the medium without glucose. In such culture conditions ectomycorrhizal ability of the IAA overproducer mutant 331 was significantly higher than of the comparable wild type. The highest content of soluble sugars was found in stems and roots of plants mycorrhizal with the mutant followed by mycorrhizal plants with the wild type and then by the uninoculated control. Sucrose practically disappeared from roots of mycorrhizal plants. Starch content in roots of mycorrhizal plants with the IAA overproducer mutant was lower as compared with other treatments. Fungal auxin in mycorrhizal symbiosis seems to be responsible for maintaining the source-sink relationship. This is revealed by higher sugar level in the host's photosynthetic tissue (source) and the rise of soluble sugar content in roots (sink) due to enhanced translocation of sugars to the roots and auxin stimulated conversion of carbohydrates (sucrose, starch) of the host.

Impact of arbuscular mycorrhizal fungi on the growth and related physiological indexes of Amorpha fruticosa

Through inoculating Amorpha fruiticosa with arbuscular mycorrhizal (AM) fungi and without, the seedlings’ growth indexes, dynamic characteristics of plant endogenous hormone levels, soluble sugar contents in roots and in leaves respectively, and physiological characteristics of seedlings utilizing nitrogen (N), phosphorous (P), were systematically studied. The results showed that both the two tested AM fungi strains, Glomus mosseaeand Glomus intraradices, could colonize the A. fruiticosa roots forming mycorrhizal complexes, and G. mosseae found to be the best AM fungus for A. fruiticosa had a better colonization compatibility than G. intraradices on A. fruiticosa roots with colonization percentage up to 88.5% that of the highest. On the one hand, inoculation with AM fungi could obviously elevate seedling heights, root collar diameter and dry biomass which were 1.94, 1.56 and 1.68 times that of control seedlings when A. fruiticosa seedlings inoculated with G. mosseae at the last stage of seedling growth (110 days). On the other hand, the soluble sugar contents in roots and leaves of seedlings inoculated with AM fungi were significantly higher than control treatments, having a positive correlation with colonization percentage. In addition, AM fungi dramatically increased the contents of auxin (IAA), gibberellin (GA) and zeatin (ZR) in roots, but had little impact on abscisic acid (ABA). Furthermore, AM fungi inoculation not only improved per seedling total N, P contents, but also significantly increased the soluble N, P concentration of rhizosphere soil. Key words: Arbuscular mycorrhizal fungi, Amorpha fruiticosa, soluble sugar, endogenous hormone, N, P element.

Effect of salinity on sodium and chloride uptake, proline and soluble carbohydrate contents in three alfalfa varieties

Salinity stress affected severely plant growth and production. Indeed, soil salinity represented one of the most important environmental stresses, which caused serious threats to agriculture and also results in the deterioration of environment. Accumulation of sodium, chloride, proline and soluble sugars was investigated in leaves, stems and roots of three alfalfa varieties (Hunterfield, Hyb.555 and Gabes) at the late bloom-early pod stage. The study was conducted in a greenhouse for 90 days of salt stress in whole-plants. Plants were irrigated with top water with four NaCl concentrations: (0 - 2.5 - 5 and 10g.l -1 ). Results showed that all varieties accumulated high Na + and Cl - contents in leaves and stems. Gabes variety differed from Hunterfield and Hyb.555 with Na + and Cl - contents significantly lower in leaves at the stressful treatments. Furthermore, Gabes proline content at 5 and 10g.l -1 NaCl in three organs was significantly higher than in the introduced varieties. Proline content in leaves, stems and roots increased with the rise of salt in pots, reaching a significantly higher level for Gabes at the stressful treatment (10g.l -1 ). Soluble sugar content in leaf tissue was higher in Gabes than those in the introduced varieties at the stressful treatments (5 and 10g.l -1 ). Contrary to the air parts (leaves and stems), soluble sugar contents in roots for Hunterfield and Hyb.555 are significantly higher, compared to Gabes variety, at the stressful treatment. This could be probably related to the difficulty in generating new leaves in Hunterfield and Hyb.555 varieties. Keyword: Alfalfa; chloride; proline; Salinity; sodium; soluble carbohydrate.

Low Magnesium with High Potassium Supply Changes Sugar Partitioning and Root Growth Pattern Prior to Visible Magnesium Deficiency in Leaves of Rice (<i>Oryza sativa</i> L.)

This research was conducted to investigate the effects of low magnesium (Mg) with high potassium (K) supply on the Mg concentration, sugar partitioning and root growth of rice (Oryza sativa L. cv. Wuyunjing 7) plants grown in hydroponics under greenhouse conditions, at Nanjing Agricultural University, China. The nutrient solution contained 0.01 and 1.0 mM Mg concentration, with K at 1.0 and 6.0 mM. Compared with the control (1mM Mg and K) treatment, the soluble sugar content at the treatment of low Mg (0.01 mM) with high K (6 mM) decreased by 35.7% in leaves, whereas increased 29.2% in roots at day 15 after treatment initiation. The shoot dry weight (DW) declined 12.9%, but root DW increased 12.1% leading to the significant increase in the root to shoot ratio at day 30. Furthermore, the total root length, total root surface area, root volume, average root diameter, total length of 0 - 0.5 mm and 0.5 - 1.0 mm diameter roots at day 30 significantly increased by 11.8%, 16.4%, 25.3%, 8.1%, 16.6% and 12.5%, respectively. Correlation analysis revealed the root to shoot ratio is closely related to the soluble sugar contents in roots and root morphological parameters of rice at day 15 and day 30. The typical visible symptoms of Mg deficiency in leaves of rice were obtained in the treatment of low Mg with high K at day 35. These findings indicated that low Mg with high K supply altered sugar partitioning and root morphological parameters, resulting in the increased root to shoot ratio prior to visible Mg deficiency symptoms in rice leaves. The increase in root to shoot ratio maybe an important adaptive mecha-nism for rice plants to respond to low-Mg stress during the early growth stage.

Effects of indole-3-acetic acid and zinc on the growth, osmotic potential and soluble carbon and nitrogen components of soybean plants growing under water deficit

Three-week old soybean (Glycine max) plants were subjected to a factorial combination of four regimes of soil matric water potential (ψm=−0·03, −0·5, −1·0 and −1·5 MPa), two levels of supplementary Zn (O and 20 mgl−1) and two levels of foliar IAA application (O and 10 mgl−1). Under control conditions (no Zn, no IAA), increasing soil drying progressively retarded shoot and root growth (length and dry mass production), reduced leaf relative water content (RWC) and decreased the contents of chlorophyll (Chl) and shoot soluble sugars (SS), but increased soluble sugar content of roots and lowered osmotic water potential of shoots and roots (osmotic adjustment). Total free amino acid (TAA) content increased in shoots but decreased in roots whereas contents of soluble proteins (SP) decreased in shoots and roots. The effect of water stress was statistically significant (p<0·05) and had a major effect (as indicated by η2values) on leaf RWC, shoot and root dry masses and osmotic potential. Supplementary Zn improved root growth at all levels of stress and shoot growth under severe stress. Improvement of growth was positively correlated with the internal tissue Zn concentrations (r=0·91 and 0·86 for shoot and 0·94 and 0·82 for root length and dry mass respectively). Exogenous IAA raised (p<0·05) RWC, Chl, DM (slightly), root SS, and SP, whereas shoot TAA was lowered. Effects on root TAA and shoot SS were more complex: they were lowered at zero stress and raised under severe stress. IAA and Zn in combination had additive effects on Chl, growth and osmotic potential, but their combined effects on SP and TAA were more complex. It is concluded that the treatment of soybean plants grown under conditions of low soil water potentials and Zn deficiency with Zn and IAA solutions counteracted the deleterious effects of stress, especially at high stress levels, and helped stressed plants to grow successfully under these adverse unfavourable conditions.

Acid invertase in mycorrhizal and non‐mycorrhizal roots of Norway spruce (Picea abies [L.] Karst.) seedlings

SUMMARYSucrolytic enyzme activities and concentrations of hexoses typically increase in plant/microbe symbioses. However, there is little information on ectomycorrhizal associations. We measured invertase activity and soluble sugar contents in roots of mycorrhizal and non‐mycorrhizal Norway spruce [Picea abies (L.) Karst.] seedlings. We used two ectomycorrhizal fungi, a basidiomycete [Amanita muscaria (L. ex Fr.) Hooker] and an ascomycete (Cenococcum geophilum Fr.). Mycorrhizas and non‐mycorrhizal short roots, as well as other parts of the root system, were investigated at different developmental stages by micro‐analytical methods.Neither sucrose nor invertase could be detected in fungal mycelia. In vitro measurable invertase activity and the sucrose, glucose and fructose content were reduced in both types of mycorrhizas compared with the non‐mycorrhizal short roots. Correction of data for the fungal component in the mycorrhizas, indicated that there were no differences in plant‐specific amounts of sucrose and acid invertase activity in mycorrhizal and non‐mycorrhizal roots. However, amounts of glucose and fructose, which are present in both partners, were clearly reduced in the mycorrhizas. As high fructose levels inhibit acid invertase, a reduction in the amount of fructose in the symbiotic tissue could favour in vivo acid invertase activity. Our results indicate that the situation in ectomycorrhizas may be different from those in other biotrophic interactions.