Regulation of Phosphorus Supply on Nodulation and Nitrogen Fixation in Soybean Plants with Dual-Root Systems

Phosphorus (P) is an important nutrient affecting nodulation and nitrogen fixation in soybeans. To further investigate the relationship of phosphorus with soybean nodulation and nitrogen fixation, the seedling grafting technique was applied in this study to prepare dual-root soybean systems for a sand culture experiment. From the unfolded cotyledon stage to the initial flowering stage, one side of each dual-root soybean system was irrigated with nutrient solution containing 1 mg/L, 31 mg/L, or 61 mg/L of phosphorus (phosphorus-application side), and the other side was irrigated with a phosphorus-free nutrient solution (phosphorus-free side), to study the effect of local phosphorus supply on nodulation and nitrogen fixation in soybean. The results are described as follows: (1) Increasing the phosphorus supply increased the nodules weight, nitrogenase activity, ureide content, number of bacteroids, number of infected cells, and relative expression levels of nodule nitrogen fixation key genes (GmEXPB2, GmSPX5, nifH, nifD, nifK, GmALN1, GmACP1, GmUR5, GmPUR5, and GmHIUH5) in root nodules on the phosphorus-application side. Although the phosphorus-application and phosphorus-free sides demonstrated similar changing trends, the phosphorus-induced increases were more prominent on the phosphorus-application side, which indicated that phosphorus supply systematically regulates nodulation and nitrogen fixation in soybean. (2) When the level of phosphorus supply was increased from 1 mg/L to 31 mg/L, the increase on the P– side root was significant, and nodule phosphorus content increased by 57.14–85.71% and 68.75–75.00%, respectively; ARA and SNA were 218.64–383.33% and 11.41–16.11%, respectively, while ureide content was 118.18–156.44%. When the level of phosphorus supply was increased from 31mg/L to 61mg/L, the increase in the regulation ability of root and nodule phosphorus content, ARA, SNA, and ureide content were low for roots, and the value for nodules was lower than when the phosphorus level increased from 1 mg/L to 31 mg/L. (3) A high-concentration phosphorus supply on one side of a dual-root soybean plant significantly increased the phosphorus content in the aboveground tissues, as well as the roots and nodules on both sides. In the roots on the phosphorus-free side, the nodules were prioritized for receiving the phosphorus transported from the aboveground tissues to maintain their phosphorus content and functionality.

Insights Into Manganese Solubilizing Bacillus spp. for Improving Plant Growth and Manganese Uptake in Maize

Manganese (Mn) is an essential micronutrient for plant growth that is involved in the structure of photosynthetic proteins and enzymes. Mn deficiency is widespread mainly in dry, calcareous, and sandy soil, which leads to a significant decrease in crop yield. Mn-reducing bacteria promote the solubilization of Mn minerals, thus increasing Mn availability in soil. The present study aimed to assess the Mn solubilizing ability and plant growth-promoting potential of Bacillus spp. strains for maize plants with insoluble Mn compounds. Several Mn-solubilizing bacterial (MSB) strains were isolated from the maize rhizosphere using nutrient agar media amended with 50 mM MnO2. These strains were screened based on qualitative and quantitative solubilization of Mn, phosphorus, potassium, and zinc and production of ammonia. The majority of MSB strains were positive for catalase, protease, amylase, and oxidase activity, while more than 60% of tested strains were positive for lipase activity, and the production of indole-3-acetic acid and siderophores. Forty-five percent of the tested strains also showed solubilization of potassium. All the MSB strains were evaluated for their ability to promote plant growth and Mn uptake in the presence of MnO2 under axenic sand culture conditions. The results revealed that inoculation with MSB strains under sand culture significantly improved the growth of maize seedlings except for strains ASH7, ASH10, and ASH12. Comparatively, strains ASH6, ASH11, ASH19, ASH20, and ASH22 demonstrated a better increase in plant growth, fresh and dry biomass, and Mn uptake in roots and shoots than the other strains tested. All of these strains were identified as Bacillus spp. through 16S rRNA partial gene sequencing. Maize inoculation with these selected identified MSB strains also resulted in an increase in maize growth and nutrient uptake in maize roots and shoots under soil culture conditions in the presence of native soil Mn. The current study highlights the importance of MSB strain inoculation which could be a potential bioinoculants to promote plant growth under Mn deficiency.

Effect of potassium supply on content of apple leaf phosphorus

Well-balanced mineral nutrition of apple trees is critical for fruit quality and storability. The seasonal changes of phosphorus and potassium leaf content were studied in the pot sand culture during the seasons of 2019 and 2020. The treatments comprised the application of the nutrient solution with different concentrations (0.00; 0.68; 1.36; 1.70; 2.04; 2.72; 3.40 g l-1). Leaves were analyzed on potassium and phosphorus content. The increase in potassium supply led to a striking increase in the content of apple leaf phosphorus above the optimal level. An approach to non-invasive detection of the impact of the nutrient imbalance based on hyperspectral reflectance imaging has been proposed.

Comparative Physiology of Drought and Salinity Stress in Grass Pea (Lathyrus sativus L.) Seedlings

Aims: The aim of this study was to investigate the effect of iso-osmotic potentials of drought and salinity on physiological parameters of grass pea seedlingsas well as to compare varietal responses. Study Design: Completely randomized design. Place and Duration of Study: In the years 2017-2018 and 2018-2019, laboratory research on grass pea varieties BK-14 and Pratik was conducted in the Department of Plant Physiology, Bidhan Chandra Krishi Viswavidyalaya, Nadia, West Bengal, India. Methodology: The effect of iso-osmotic potential of salinity and drought stress was studied using NaCl (50, 100 and 200 mM ) and PEG 6000 (10, 12 and 18%) solutions with -0.2, -0.4, and -0.8 MPa osmotic potential, and the experiment was carried out in sand culture using modified Hoagland solution under diffused light, at about 80±1% relative humidity (R.H.) and a temperature of 22±1oC. Data on different physiological and biochemical parameters were recorded after ten days of seedling growth in sand culture. Statistical analysis was performed on the mean data in all cases following completely randomized design (CRD) by application of INDOSTAT version 7.1 software. Results: The germination of grass pea seeds was more severely affected by drought stress than salinity. Both stresses had a negative impact on most of the parameters studied except for leaf proline and sugar The impact became more pronounced as the severity of the stress increased. The highest intensity of drought stress was found to be more detrimental to leaf protein and relative water content in BK 14, while Pratik was more drastically affected by the highest level of salinity. Drought was found to have a significant negative impact on leaf starch in both the grass pea varieties. The highest concentration of PEG led to a remarkable increase in leaf proline. Conclusion: The mild to moderate levels (-0.2 and -0.4 MPa) of stress did not produce much severe effects on the grass pea seedlings, but the highest intensity of stress with an osmotic potential of -0.8 MPa mostly produced drastic effects. There were varietal differences in response to two abiotic stresses. In general, drought stress was found to cause more negative effects on seedling than iso-osmotic potential of salinity stress.

A Physiological Approach to Study the Interaction of Cadmium and Zinc in Groundnut (Arachis hypogaea L.) Seedlings

Background: Heavy metal toxicity affects plant growth and alters physiological processes. Soils in many areas are often contaminated by cadmium and zinc which show varied response on plants by their interactive effects. The experiment was done to study the effect of cadmium and zinc as sole presence and in combination in groundnut seedlings. Methods: The laboratory experiment was conducted on groundnut cultivar TG 51 in sand culture using modified Hoagland solution. After initial screening, three concentrations of cadmium (Cd 100, Cd 300 and Cd 500 µM) and two concentrations of zinc (Zn 50 and Zn 150 ìM) were selected for studying their effects individually and in combination on physiological and biochemical parameters. Result: The reduction in root length increased over control as the concentration of cadmium in the medium increased. Cadmium or zinc alone led to a decrease in chlorophyll a, b and relative water content of the leaf. Zinc supplement at 150 µM not only mitigated the negative effect of Cd 100 µM and 300 µM, but also increased the chlorophyll content above control level. Zinc supplement not only increased the protein content over the control but also mitigated to some extent the adverse effects of cadmium in protein content when applied in combination. Under both cadmium and zinc treatment, the inhibition of nitrate reductase (NR) activity over unstressed control was found. Different treatment combinations, however, reduced the negative effects of cadmium, although zinc could not completely override such damage, change the level of toxicity. Treatment with Cd 100 µM and 300 µM induced an increase in phenol content over the control, while higher concentration (500 µM) of the metal led to a decrease in this potent antioxidant compound. Presence of Zinc in the growing medium significantly enhanced the accumulation of phenolic compounds highlighting its protective role against oxidative damage.

Anatomical changes in chickpea (Cicer arietinum L.) under aluminium stress condition

An experiment was conducted to investigate the effect of aluminium (Al) toxicity on the anatomical changes in the root, stem and leaf of chickpea (Cicer arietinum L.) plants grown in sand culture. Toxicity of Al reduced the length of primary root and the number of lateral roots of chickpea than that of the control. Aluminium decreased the size and number of vessels in the root of chickpea. Larger area of sclerenchyma cells was noticed in the stem of Al-stressed plant. Number of palisade parenchyma was reduced in the leaf of chickpea. Aluminium treatment caused closure of stomata. Increased number of trichomes in chickpea leaves was also reported due to aluminium. Dhaka Univ. J. Biol. Sci. 30(2): 187-196, 2021 (July)

Role of nitrogen deficiency on growth and development near isogenic by E genes lines of soybean co-inoculated with nitrogen-fixing bacteria

Nitrogen deficiency is a limiting factor in increasing efficiency of crop production in terrestrial ecosystems, and the transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil microorganisms. Symbiotic nitrogen-fixing bacteria and roots depend on each other and have developed various mechanisms for symbiotic coexistence. The aim of this work was to investigate the role of nitrogen deficiency on growth and development near isogenic by E genes lines of soybean (Glycine max (L.) Merr.): short-day (SD) line with genotype Е1е2е3(Е4е5Е7), and photoperiodic insensitive (PPI) line with genotype е1е2е3(Е4е5Е7) grown from seeds inoculated with active strains of Bradyrhizobium japonicum against the background of local populations of diazotrophs of the genus Azotobacter spp. and establish how the soybean – Bradyrhizobium symbiosis will develop as the genes of both microsymbionts and macrosymbionts are responsible for the formation of the symbiotic complex. Plants were grown in a vegetation chamber, in sand culture. To assess the quantitative composition of microorganisms in the rhizosphere and rhizoplanes, 6 plants were selected from each soybean line, then separation of the zones of the rhizosphere and rhizoplanes was performed using the method of washing and the resulting suspension was used for inoculation on dense nutrient media (mannitol-yeast agar medium and Ashby medium). The results of study showed that seed inoculation and co-inoculation provides faster formation of the symbiotic soybean – Bradyrhizobium complex. Differences in nodulation rates between the short-day line with genotype Е1е2е3(Е4е5Е7), and a photoperiodic insensitive line with genotype е1е2е3(Е4е5Е7) were identified. Determination of the amount of B. japonicum on the medium of mannitol-yeast agar in the rhizosphere and rhizoplane showed that inoculation by B. japonicum strain 634b caused a significant increase in the amount B. japonicum in the rhizosphere and rhizoplane in both soybean lines, comparison with non-inoculated seeds. Then, co-inoculation by B. japonicum strain 634b + Azotobacter chroococcum significantly increased the amount of B. japonicum only in the rhizoplane and decreased their number in the rhizosphere. Determination of the amount of A. chroococcum on the Ashby elective medium in the rhizosphere and rhizoplane showed that the inoculation by B. japonicum strain 634b caused a significant decrease in the amount of A. chroococcum both in the rhizosphere and in the rhizoplane of the PPI line of soybean, and in the rhizosphere the SD line, in comparison with non-inoculated seeds. That can testify to the competitive interaction of these microorganisms. However, the co-inoculation by B. japonicum strain 634b + A. chroococcum in the SD line significantly increased the number of A. chroococcum in the rhizoplane and decreased their number in the rhizosphere, in the PPI line their number decreased in the rhizoplane and increased in the rhizosphere, in comparison with non-inoculated seeds. Probably, the E genes (their dominant or recessive state) of soybean isogenic lines affect the regulation of the content and distribution of sugars. It was established that the nitrogen deficiency stimulated development of the root system of plants and the synthesized sugars were distributed predominantly to the root system growth. We suppose that the seeds’ inoculation had extended sugar consumption to the symbiont, due to which it compensates the lack of nitrogen, but leads to a slower growth of the root system.

Enhancing Productivity of Sweet Marjoram in Substrate Culture

Sweet Marjoram is considered as one of the important herbal plants, grown in many countries for medical and nutritional purposes and is an abundant source of valuable biologically active substances and mineral components. An experiment has been carried out on sweet marjoram at the experimental site of Central Laboratory for Agricultural Climate (CLAC), Agriculture Research Center, Ministry of Agriculutre and land reclamation, Egypt under a net duble span house, during seasons of 2019and 2020. The experiment was carried out to study the effect of different nutrient solution sources and verimicompost rates on production of Sweet Marjoram grown in sand culture. In this experiment, Three sources of nutrient solution were under investigation (chemical nutrient solution “CN. S.” as a control treatment, vermi-liquid “V. L.” and mixture of chemical nutrient solution andvermi-liquid (50%:50%) “CN.S.+V.L.”), also, five rates of vermicompost have been added to sand culture(zero% of vermicompost "V.C. 0%"as a control treatment, 10% Vermicompost "V.C. 10%", 20% Vermicompost "V.C. 20%", 30% Vermicompost "V.C. 30%"and 40% Vermicompost "V.C. 40%").Regarding the effect of nutrient solution source; results illustrated that chemical nutrient solution recorded the highest values for vegetative growth, yield and chemical measurments. also data clearfied that the mixture of chemical nutrient solution and vermi-liquid (50%:50%) “CN.S.+V.L.” recorded a promising results very close to the chemical nutrient solution and more healther; because the amount of chemicals used in this nutrient solution have been reduced into the half amount only comparison with chemical nutrient solution. For that, the mixture of chemical nutrient solution and vermi-liquid (50%:50%) could be considered as the most suitable nutrient solution for sweet marjoram. Concerning the effect of different vermicompost rates, results showed that adding vermicompost rate by 30% to sand culture recorded the highest values for plant height, number of branches /plant, Fresh and dry weights of the aerial parts /plant, yields of the fresh and dry herb/ m2, yield of aromatic oil/ m2 (V.C. 40% recorded higher values for yield of the aromatic oil/m2 than V.C. 30% but the difference between both of them was not significant), and N,P,K% in leaves.

Morphogenesis, pigment content, phytohormones and productivity of sweet pepper under the action of gibberellin and tebuconazole

One of the main tasks of modern plant physiology is regulation of growth and development of cultivated plants in order to optimize the productive process. The attention of the scientific community is focused on the use of natural activators and growth inhibitors. We investigated the effect of foliar treatment with 0.005% solution of gibberellic acid (GA3) and 0.025% solution of the antigibberellic preparation tebuconazole (EW-250) on morphogenesis, leaf mesostructure, the content of photosynthetic pigments, the balance of endogenous phytohormones and productivity of Capsicum annuum L., Antey variety. The vegetation experiment was carried out in the conditions of soil-sand culture in vessels with a volume of 10 L. Treatment of plants was carried out in the budding phase. Morphometric parameters were determined every 10 days. The mesostructure of the middle tier leaves was studied in the fruit formation phase, and the chlorophyll content was determined in the raw material by spectrophotometric method. Analytical determination of endogenous phytohormones – indolyl-3-acetic (IAA), gibberellic (GA3) and abscisic (ABA) acids and cytokinins – zeatin (Z), zeatin-O-glucoside (ZG), zeatinribozide (ZR), isopentenyladenine (iP) and isopentenyladenosine (iPA) were performed by high performance liquid chromatography – mass spectrometry (HPLC-MS). With GA3 treatment, plant height increased considerably, while with EW-250, it decreased. Both regulators led to an increase in the number of leaves on the plant, the leaf raw biomass, stems and roots and the dry matter of the whole plant, the area of a single leaf blade and the total area of leaves on the plant. Under the action of EW-250, the chlorophyll content in the leaves surged, while under the action of GA3 it tended to decrease or did not change at all. Both regulators thickened the chlorenchyma and boosted the volume of the columnar parenchyma cells. GA3 treatment induced a rise in the thickness of the upper and lower epidermis, and EW-250 led, on the contrary, to a decrease. It is shown that after treatment with exogenous GA3, the content of endogenous IAA and ABA decreased and GA3 in plant stems increased. Instead, EW-250 caused a decrease in the levels of GA3, IAA and ABA in the stems. Exogenous GA3 enhanced the accumulation of endogenous GA3 and IAA and inhibited ABA in the leaves. Under the action of the retardant, the level of ABA in the leaves did not change, while GA3 and IAA decreased. Treatment of plants with the studied growth regulators caused a decrease in the pool of cytokinins (CK) in stems. EW-250 showed a significant rise in the hormone content in the leaves. After spraying with GA3 solution, the level of ZG, Z and ZR grew. Under the action of the retardant, the increase in the CK pool occurred exclusively due to the iP. Growth regulators optimized the productivity of sweet pepper plants: under the action of GA3 there was an increase in the number of fruits per plant, and after the use of EW-250 there was a rise in the average weight of one fruit. The obtained results showed that anatomical-morphological and structural-functional rearrangements of sweet pepper plants under the action of exogenous gibberellic acid and EW-250 took place against the background of changes in the balance and distribution of endogenous hormones. Increased photosynthetic activity, stimulation of growth processes of some plant organs and inhibition of others enlarged biological productivity of the culture.

Changes in Species Abundances with Short-Term and Long-Term Nitrogen Addition are Mediated by Stoichiometric Homeostasis

Aims Increasing nitrogen (N) deposition altered plant communities globally, however the changes in species abundances with short-term vs. long-term N enrichment remains unclear. Stoichiometric homeostasis (H) is a key trait predictive of plant species dominance and species responses to short-term global changes. It is unknown whether N enrichment can alter H over time, thereby affecting species responses to long-term N addition. Methods Here we address these two knowledge gaps with three representative species in a long-term N addition experiment and a sand culture experiment. Results The abundance of Leymus chinensis decreased with short-term N addition, and increased with long-term N addition, while Chenopodium glaucum showed opposite pattern. Cleistogenes squarrosa was only favored by 1-year N addition, and depressed by two and more years of N addition. The H values of L. chinensis and C. glaucum decreased significantly with long-term N addition however did not change for C. squarrosa. Conclusion The decrease of H suggested the nutrients use strategy became more progressive, which mediated the responses of species abundances to short- and long-term N addition. We anticipate our research to be a starting point for explaining ecosystems function and process in response to global change from the perspective of species adaptability mediated by H.