Effect of irrigation with saline magnetized water and different soil amendments on growth and flower production of Calendula officinalis L. plants

Global climate change and increased population caused significant depletion of freshwater especially in arid and semi-arid regions including Saudi Arabia. Saline water magnetization before irrigation may help in alleviating the adverse effects of salinity on plants. The current study aimed to examine the potential beneficial effects of water magnetization and soil amendments on growth, productivity, and survival of Calendula officinalis L. plants. Three types of water (tap water “control”, well water, and magnetized well water) and two types of soil amendments (Fe₂SO₄ and peat moss) were examined. Our results showed that irrigating C. officinalis plants with saline well water (WW) adversely affected growth and flowering as compared to tap water (TW). However, plants irrigated with magnetized water (MW) showed significant enhancement in all the studied vegetative and flowering growth parameters as compared to those irrigated with WW. Furthermore, mineral contents and survival of C. officinalis plants irrigated with MW were higher than those irrigated with TW. Irrigation with MW significantly reduced levels of NA⁺ and Cl⁻ ions in leaves of C. officinalis plants indicating the role of magnetization in alleviating harmful effects of salinity. The current study showed that water magnetization enhanced water quality and increased plant’s ability to absorb water and nutrients. Further studies are needed to examine the possibility of irrigating food crops with magnetized water.     

Role of Organic Amendments to Mitigate Cd Toxicity and Its Assimilation in <i>Triticum aestivum</i> L.

In soil biota, higher and enduring concentration of heavy metals like cadmium (Cd) is hazardous and associated with great loss in growth, yield, and quality parameters of most of the crop plants. Recently, in-situ applications of eco-friendly stabilizing agents in the form of organic modifications have been utilized to mitigate the adverse effects of Cd-toxicity. This controlled experiment was laid down to appraise the imprints of various applied organic amendments namely poultry manure (PM), farmyard manure (FYM), and sugarcane press mud (PS) to immobilize Cd in polluted soil. Moreover, phytoavailability of Cd in wheat was also accessed under an alkaline environment. Results revealed that the addition of FYM (5–10 ton ha^-1 ) in Cd-contaminated soil significantly increased germination rate, leaf chlorophyll content, plant height, spike length, biological and grain yield amongst all applied organic amendments. Moreover, the addition of FYM (5–10 ton ha^-1 ) also reduced the phytoavailability of Cd by 73–85% in the roots, 57–83% in the shoots, and 81–90% in grains of wheat crop. Thus, it is affirmed that incorporation of FYM (5–10 ton ha^-1 ) performed better to enhance wheat growth and yield by remediating Cd. Thus, the application of FYM (5–10 ton ha^-1 ) reduced the toxicity induced by Cd to plants by declining its uptake and translocation as compared to all other applied organic amendments to immobilize Cd under sandy alkaline polluted soil.     

Influence of arbuscular mycorrhizae on heavy metal (Zn and Pb) uptake and growth of Lygeum spartum and Anthyllis cytisoides

The hypothesis tested in this paper is that, because the freshest water occurs in the largest soil pores (macropores), plants of low to moderate transpiration rate can survive in salinized soil because they preferentially extract water from macropores. The hypothesis predicts that a plant growing in a macroporous soil should have greater growth under a given salinity treatment than a similar plant growing in a soil with the same mineralogy but without macropores. This hypothesis was tested by growing bell pepper (Capsicum annuum) in the greenhouse in pots filled with either a commercial fritted clay (a highly macroporous soil) or the same clay ground to a finer texture and sieved to remove macropores and produce a microporous soil. The pots sat in pans filled with salt water. Half of the pots were irrigated once a day with fresh water and the other half received no fresh water. Plants growing in the macroporous soil had greater growth for a given salinity treatment than the plants growing in the microporous soil under both the irrigated and non-irrigated conditions. Under the irrigated condition for the highest salinity treatment, the non-reproductive fresh weight per plant, total dry weight per plant and fruit fresh weight per plant was 114 g, 12 g and 50 g, respectively, for the macroporous soil and 47 g, 4.5 g and 5 g, respectively, for the microporous soil. The results of this study provide evidence to suggest that a better understanding of what constitutes a good structure in a saline soil may aid us in our efforts to improve the management of saline soils. We suggest that it may be possible to increase the agricultural production on salinized land by no-tillage agriculture which preserves macroporosity. Possible obstacles could be the tendency of field saline-sodic soils to swell and the unavailability of relatively fresh irrigation water in areas with saline soils.     

Organic Amendments Improve Plant Morpho-Physiology and Antioxidant Metabolism in Mitigating Drought Stress in Bread Wheat (<i>Triticum aestivum</i> L.)

Due to the unpredictable climate change, drought stress is being considered as one of the major threats to crop production. Wheat (Triticum aestivum L. cv. BARI Gom-26) being a dry season crop frequently faces scarcity of water and results in a lower yield. Therefore, this experiment aims to explore the role of different organic amendments (OAs) in mitigating drought stress-induced damage. The pot experiment consisted of different organic amendments viz. compost, vermicompost and poultry manure @0.09 kg m⁻² soil, biochar @2.5% w/w soil and chitosan @1% w/w soil which was imposed on the plants grown under both well-watered and drought conditions. Results showed that drought stress reduced plant height (15%), SPAD value (16%), relative water content (13%), number of spikelet spike⁻¹ (17%), number of grains spike⁻¹ (12%), and 100-grain weight (18%). Organic amendments act as a protectant and reduce drought stress-induced damages by enhancing the morpho-physiological and yield attributes. Vermicompost enhanced SPAD value by 18%, number of spikelets spike⁻¹ by 20%, number of grains spike⁻¹ by 17%, whereas poultry manure increased plant height by 16% under drought condition compared to control plant. Unlike other OAs applied, vermicompost was proved to be capable of reducing the higher lipid peroxidation and proline content raised by drought condition. Drought stress-induced increment of catalase, ascorbate peroxidase and glutathione reductase activities were also efficiently modulated by the organic amendment application. The present study concluded that OAs play significant roles in alleviating drought stressinduced damages by improving the morpho-physiological attributes and among the different types of OAs used vermicompost performed better which in addition ceased the production of reactive oxygen species.     

Antifungal Potential of <i>Beauveria bassiana</i> on <i>Solanum lycopersicum</i> L. Infected with <i>Fusarium oxysporum</i> f. sp. <i>lycopersici</i>

The objective of this work was to evaluate the effect of Beauveria bassiana (Bb 1205) on controlling Fusarium oxysporum f. sp. lycopersici (Fol 17108) in tomato plants in greenhouse conditions. Inoculation of Bb 1205 was the most promising among the agronomic variables and expression of the activity of the enzymes β-1,3-glucanases and chitinases. Inoculation of Bb 1205 occurred at a concentration of 1 × 10⁸ conidia·mL⁻¹, which was administered onto the leaves, directly into the soil and via injection. Infection with Fol 17108 occurred with 1 × 10⁶ spores·mL⁻¹, which were added directly to the soil. Spectrophotometry was used for measuring agronomic parameters, namely activity of chitinases and β-1,3-glucanases in foliage and roots. When Bb 1205 was added to the soil, the chlorophyll index and aerial part length showed significant differences. In addition, it was determined that root length, fresh weight of foliage, flower, and fruit count increased 82 days after inoculation (dai). Chitinase activity induced by Bb 1205 in leaves and roots of tomato plants infected with Fol 17108 was observed when injected into the stem at 32 dai (41.8 and 11.6-fold, respectively). Inoculation on the foliage showed a 10-fold increase of β-1,3-glucanases in the roots after 82 dpi. As for leaves, a 3.8-fold increase was found when the stem was inoculated. In the different in vivo applications, Bb 1205 activated its defenses by expressing the chitinase enzymes and β-1,3-glucanase, thus reducing the damage caused by Fol 17108, demonstrating increase plant growth thereafter.     

Foliar and root absorption of Na+ and Cl− in maize and barley: Implications for salt tolerance screening and the use of saline sprinkler irrigation

Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m^–1 (30 mM NaCl and 2.8 mM CaCl₂) and for barley in 1994, 9.6 dS m^–1 (47 mM NaCl and 23.5 mM CaCl₂). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na⁺ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl^– concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na⁺ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na⁺ over Cl^– whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na⁺ and Cl^– than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na⁺ and Cl^– transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers     

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Summary Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg^–1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m^–1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low ( 0.2 mmol kg^–1 NaHCO₃-extractable P) at soil saturation extract salinities from 1.1 dS m^–1 to 8.8 dS m^–1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m^–1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.     

Effect of Water Stress Induced by Polyethylene Glycol on Growth,Proline Accumulation in <i>Agave americana</i> L.

The effect of water deficit was determined on both in vitro and soil seedling as well as in cells in suspension of Agave americana L. In order to do the establishment of cells, the formation of callus was induced; for it two auxins were evaluated: 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-mino-3,5,6-trichloropicolinic acid (picloram) at three concentrations (0.25, 0.5 and 0.75 mg L⁻¹) in three explants (leaf, root and meristems) cultured in MS semisolid medium. The callogenesis response was related to the type and section of the explant, as well as the regulator used, and a cell suspension was established using 0.5 mg L⁻¹ naphthaleneacetic acid (NAA) + 0.5 mg L⁻¹ Benzylaminopurine (BAP). Seedlings were exposed to polyethyleneglycol (15% and 30% w/v) with a water potential of −0.87 and −2.67 MPa, respectively, under soil conditions. Water stress was applied through restricted irrigation. Fresh weight, root system growth, and chlorophyll concentration were some of the parameters that were affected by the effect of water deficit on A. americana L. Chlorophyll concentration values were significantly decreased by 15 at 30% PEG (19.6 SPAD units) compared to the control treatment. In in vitro plants, the highest concentration of proline was found in the roots, being the treatment with 30% polyethylene glycol where the highest concentration of this osmoregulator was obtained (62.5 mg g⁻¹ DW). Under restricted irrigation conditions, an increase in proline concentration was observed both in the aerial part (2.2 µg 100 g⁻¹ DW) and in the root system (1.8 µg 100 g⁻¹ DW). However, the concentrations found were approximately ten times greater, less than those found under in vitro conditions. Therefore, the accumulation of proline can be considered an indicator of stress in Agave Americana L. growth in vitro.     

Over-expression of a vacuolar Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> antiporter gene improves salt tolerance in an upland rice

To develop a salt-tolerant upland rice cultivar (Oryza sativa L.), OsNHX1, a vacuolar-type Na⁺/H⁺ antiporter gene from rice was transferred into the genome of an upland rice cultivar (IRAT109), using an Agrobacterium-mediated method. Seven independent transgenic calli lines were identified by polymerase chain reaction (PCR) analysis. These 35S::OsNHX1 transgenic plants displayed a little accelerated growth during seedling stage but showed delayed flowering time and a slight growth retardation phenotype during late vegetative stage, suggesting that the OsNHX1 has a novel function in plant development. Northern and western blot analyses showed that the expression levels of OsNHX1 mRNA and protein in the leaves of three independent transgenic plant lines were significantly higher than in the leaves of wild type (WT) plants. T₂ generation plants exhibited increased salt tolerance, showing delayed appearance and development of damage or death caused by salt stress, as well as improved recovery upon removal from this condition. Several physiological traits, such as increased Na⁺ content, and decreased osmotic potential in transgenic plants grown in high saline concentrations, further indicated that the transgenic plants had enhanced salt tolerance. Our results suggest the potential use of these transgenic plants for further agricultural applications in saline soil.     

Green roof <Emphasis Type="Italic">Petunia</Emphasis>, <Emphasis Type="Italic">Ageratum</Emphasis>, and <Emphasis Type="Italic">Mentha</Emphasis> responses to water stress,seaweeds, and trinexapac-ethyl treatments

The availability of sufficient irrigation water and the development of drought-tolerant species are challenging factors in the design and maintenance of green roofs in modern cities. Green roof plants of Petunia hybrid Headliner^® Red Star, Ageratum hybrid Artist^® blue, and Mentha spicata L. grown in a simulated green roof pot system under controlled greenhouse conditions. The plants were watered every 2 or 6 days (2DWI/6DWI) for 8 weeks accompanied by either a 6-day treatment of seaweed extracts of Ascophyllum nodosum as a soil drench or foliar spray, or two concentrations of trinexapac-ethyl (TE) biweekly sprays. Following treatments, leaf number, leaf area, dry weights, plant height, stomatal conductanse, photosynthetic and transpiration rates and leaf water potential and relative water content were determined in two seasons during 2016 and 2017. The prolonged irrigation intervals reduced plant growth as revealed by morphological and physiological parameters. The application of SWE as drench treatment improved Petunia and Ageratum plant vegetative growth, stomatal conductance, photosynthetic and transpiration rates and leaf water potential and relative water content during prolonged irrigation intervals. TE increased the vegetative growth as well as the physiological performance of Ageratum plants. However, neither SWE nor TE treatments improved the performance of Mentha plants under prolonged irrigation intervals. It was suggested that improved photosynthetic rates were stimulated by enhanced stomatal conductance leading to improved leaf water potential as well as increased relative water content during prolonged irrigation conditions.     

<i>Azospirillum brasilense</i> and <i>Saccharomyces cerevisiae</i> as Alternative for Decrease the Effect of Salinity Stress in Tomato (<i>Lycopersicon esculentum</i>) Growth

The salinity stress is one of the most relevant abiotic stresses that affects the agricultural production. The present study was performed to study the improvement of the salt tolerance of tomato plants which is known for their susceptibility to salt stress. The present study aimed to assess to what extent strain Azospirillum brasilense (N040) and Saccharomyces cerevisiae improve the salt tolerance to tomato plants treated with different salt concentration. The inoculant strain A. brasilense (N040) was previously adapted to survive up to 7% NaCl in the basal media. A greenhouse experiment was conducted to evaluate the effect of this inoculation on growth parameter such as: plant height, root length, fresh and dry weight, fruits fresh weight, chlorophyll content, proline and total soluble sugar in tomato plants under salt stress condition. The results revealed that co-inoculation of Azospirillum brasilense (N040) and Saccharomyces cerevisiae significantly increased the level of proline (8.63 mg/g FW) and total soluble sugar (120 mg/g FW) of leaves under salinity condition comparing to non-inoculated plants (2.3 mg/g FW and 70 mg/g FW, respectively). Plants co-inoculated with adapted strain of A. brasilense and S. cerevisiae showed the highest significant (p < 0.01) increase in fruit yield (1166.6 g/plant), plant high (115 cm) and roots length (52.6) compared whit un-inoculated control plants (42 g/pant, 43.3 cm and 29.6 cm, respectively). In contrast, Na⁺ ion content was significantly decreased in the leaves of salt stressed plants treated with the A. brasilense (N040) and S. cerevisiae. Finally, the results showed that dual benefits provided by both A. brasilense (N040) and S. cerevisiae can provide a major way to improve tomato yields in saline soils.     

EDTA-Facilitated Phytoremediation of Soil with Heavy Metals from Sewage Sludge

The objective of this research was to determine the effect of the chelate EDTA (ethylenediaminetetraacetic acid), which is used in phytoremediation, on plant availability of heavy metals in liquid sewage sludge applied to soil. Sunflower (Helianthus annuus L.) was grown under greenhouse conditions in a commercial potting soil; the tetrasodium salt of EDTA (EDTA Na₄) was added at a rate of 1 g kg^-1 to half the pots. Immediately after seeds were planted, half of the pots with each soil (with or without EDTA) were irrigated with 60 ml sludge, and half were irrigated with 60 ml tap water. For the subsequent five irrigations, plants in soil with EDTA received either sludge or tap water containing 0.5 g EDTA Na₄ per 1000 ml, and plants in soil without EDTA received sludge or tap water without EDTA. Of the four heavy metals whose extractable concentrations in the soil were measured (Cu, Fe, Mn, and Zn), only Zn had a higher concentration in sludge-treated soil with EDTA compared to sludge-treated soil without EDTA. The concentrations of Fe, Cu, and Mn were similar in sludge-treated soil with and without EDTA. Of the three heavy metals whose total concentrations in the soil were measured (Cd, Pb, Cr), Pb (<10 mg kg^-1) and Cd (< 1 mg kg^-1) were below detection limits, and Cr was unaffected by treatment. The concentration of all measured elements in plants (Cd, Cu, Fe, Zn, Pb) was higher than the concentrations measured in the soil. With no EDTA, sludge-treated plants had a higher concentration of the five heavy elements than plants grown without sludge. Cadmium was lower in sludge-treated plants with EDTA than plants with EDTA and no sludge. After treatment with EDTA, the concentrations of Cu, Fe, and Zn were similar in plants with and without sludge. Lead was higher in plants with EDTA than plants without EDTA, showing that EDTA can facilitate phytoremediation of soil with Pb from sewage sludge.     

Influence of arbuscular mycorrhizal fungi and kinetin on the response of mungbean plants to irrigation with seawater

Increasing use of saline water in irrigation can markedly change the physical and chemical properties of soil. An experiment was carried out to investigate the interaction between the mycorrhizal fungus Glomus clarum, isolated from a saline soil, and kinetin on the growth and physiology of mungbean plants irrigated with different dilutions of seawater (0, 10, 20, and 30%). The growth, chlorophyll concentration and sugar content of mycorrhizal plants was greater than that of non-mycorrhizal plants under all conditions (with or without seawater). The dry weight of both mycorrhizal and non-mycorrhizal mungbean plants irrigated with 10% seawater was significantly increased by treatment with kinetin. The mycorrhizal symbiosis increased root:shoot dry weight ratio, concentrations of N, P, K, Ca and Mg, plant height, protein content, nitrogen or phosphorus-use efficiencies, and root nitrogenase, acid or alkaline phosphatase activities of seawater-irrigated mungbean plants, with little or no effect of kinetin. Kinetin treatment generally decreased chlorophyll concentration and sugar content in mycorrhizal plants as well as Na/N, Na/P Na/K, Na/Ca and Na/Mg ratios. Root colonization by G. clarum was increased by irrigation with seawater, and kinetin had no consistent effect on fungal development in roots. This study provides evidence that arbuscular mycorrhiza can be much more effective than kinetin applications in protecting mungbean plants against the detrimental effects of salt water.     

Brief pre- and post-irrigation sprinkling with fresh water reduces foliar salt uptake in maize and barley sprinkler irrigated with saline water

Brief pre- and post-irrigation sprinkling treatments using freshwater were tested to determine if these practices could reduce the uptake of salts through leaves when saline water is used to sprinkler irrigate crops. Maize and barley were sprinkler irrigated 2 to 3 times per week for 30 min with saline water (4.2 dS m^–1, 30 mmol L^–1 NaCl and 2.8 mmoles L^–1 CaCl₂ for maize and 9.6 dS m^–1, 47 mmoles L^–1 NaCl and 23.5 mmoles L^–1 CaCl₂ for barley) in separate experiments with plants grown in pots outdoors. The soil surface of all pots was covered to prevent salinization of the soil by the sprinkling water. One half of the sprinkled plants was grown in nonsaline soil to study the effects of pre-wetting and post-washing when ion uptake was primarily through leaves. The other half of the sprinkled plants was grown in soil salinized by drip irrigation, in order to evaluate the effects of pre-wetting and post-washing when Na⁺ and Cl^- uptake was through both leaves and roots.Post-washing with freshwater (5 min) reduced the leaf sap concentrations of Cl^- in saline-sprinkled plants from 56 to 43 mmol L^–1 in maize and from 358 to 225 mmol L^–1 in barley (averages for plants grown in nonsaline and saline soil). Na⁺ concentrations in leaf sap were reduced from 93 to 65 mmoles L^–1 (maize) and from 177 to 97 mmoles L^–1 (barley) by the post-washing. Pre-wetting had a small effect on ion uptake through leaves, the only significant reduction in seasonal means being in leaf Na⁺ concentrations for plants grown in nonsaline soil. Pre-wetting and post-washing, when combined, reduced leaf Cl^- concentrations to levels similar to those of nonsprinkled plants grown in saline soil; however, Na⁺ concentrations in leaves remained 3.5 times (maize) and 1.5 times (barley) higher than those of nonsprinkled plants. When pre-wetting and post-washing were not applied, sprinkled barley plants grown in saline soil had grain yields which were 58% lower than nonsprinkled plants grown in saline soil, but the reduction in grain yield was only 17% when the freshwater treatments were given. We conclude that a brief period of post-washing with freshwater is essential when saline water is employed in sprinkler irrigation. By comparison, the benefits from pre-wetting were small in these experiments. ei]T J Flowers     

Case study of a biological control: <Emphasis Type="Italic">Geobacillus caldoxylosilyticus</Emphasis> (IRD) contributes to alleviate salt stress in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) plants

The inevitable exposure of crop plants to salt stress is a major environmental problem emerged from the presence of excess NaCl radicals in the soil. Handling the problem in maize plants using a biological agent was the main interest of the present study. The non-pathogenic, halophytic, facultative aerobic bacterium Geobacillus caldoxylosilyticus IRD that was isolated from Marakopara pond in the Atoll Tikehau (French Polynesian, 2005) and found tolerant to salt stress until 3.5% NaCl (w/v). An artificial symbiosis was achieved by inoculating Geobacillus sp. into 5-day-old maize cultivars of triple hybrids (321 and 310) and singlet hybrids (10 and 162). Thereafter, maize seedlings were exposed to 350 mmol NaCl for 10 days. The data revealed that Geobacillus sp. had interacted with salinized maize and improved maize overall growth, dry weight and relative water content. Na⁺ accumulation was six times less and Cl⁻ accumulation was 13 times less in the tips of salinized maize seedlings upon Geobacillus sp. inoculation. Salinized maize without Geobacillus viewed decayed cortical cells of seedlings. In addition, proline content was two times higher in salinized seedlings lacking Geobacillus. Photosynthetic pigments and antioxidant enzymes were significantly regulated upon inoculation. Beyond this study, we presented a novel insight into a possible role of Geobacillus caldoxylosilyticus bacteria in controlling/protecting maize plants against high salt stress.     

Long‐term effect of salinity on plant quality,water relations,photosynthetic parameters and ion distribution in Callistemon citrinus

The effect of saline stress on physiological and morphological parameters in Callistemon citrinus plants was studied to evaluate their adaptability to irrigation with saline water. C. citrinus plants, grown under greenhouse conditions, were subjected to two irrigation treatments lasting 56 weeks: control (0.8 dS·m^?1) and saline (4 dS·m^?1). The use of saline water in C. citrinus plants decreased aerial growth, increased the root/shoot ratio and improved the root system (increased root diameter and root density), but flowering and leaf colour were not affected. Salinity caused a decrease in stomatal conductance and evapotranspiration, which may prevent toxic levels being reached in the shoot. Net photosynthesis was reduced in plants subjected to salinity, although this response was evident much later than the decrease in stomatal conductance. Stem water potential was a good indicator of salt stress in C. citrinus. The relative salt tolerance of Callistemon was related to storage of higher levels of Na⁺ and Cl^? in the roots compared with the leaves, especially in the case of Na⁺, which could have helped to maintain the quality of plants. The results show that saline water (around 4 dS·m^?1) could be used for growing C. citrinus commercially. However, the cumulative effect of irrigating with saline water for 11 months was a decrease in photosynthesis and intrinsic water use efficiency, meaning that the interaction of the salinity level and the time of exposure to the salt stress should be considered important in this species.     

<i>In Vitro</i> Propagation of <i>Agave guiengola</i> Gentry Using Semisolid Medium and Temporary Immersion Bioreactors

Agave guiengolaGentry is an endemic plant from a very small locality in Oaxaca, Mexico. Its conservation status is fragile and can rapidly worsen. Because of its scarcity, this agave has been used solely for ornamental purposes, but it could have other uses if more plants were available. In vitro propagation by enhanced axillary sprouting from stem segments was attained using Murashige and Skoog Basal Medium (MS) as well as basal medium supplemented with cytokinins 6-Benzylaminopurine (BA) or 6-(γ,γ-Dimethylallylamino)purine (2iP). The best treatment for shoot induction in semisolid medium consisted in MS supplemented with 2 mg l^–1 BA, obtaining a mean of 3.7 shoots per explant. Other interesting responses were observed, such as nodular callus induction using combinations of BA and 2,4-Dichlorophenoxyacetic acid (2,4-D); root induction without Plant Growth Regulators (PGR); and generation of shoot clusters. These clusters constituted an excellent explant for micropropagation in temporary immersion bioreactors, obtaining a propagation rate of 43 shoots per explant with 1 min immersion and 6 h immersion frequencies. All new plants rooted and survived the transfer to soil. This study developed an in vitro propagation scheme to produce individuals that can be used either for reforestation, economical purposes, or to carry out studies in this species to assess its full potential, avoiding exploitation from wild plants.     

Long-term responses of Melilotus segetalis to salinity. I. Growth and partitioning

Annual sweetclover plants [Melilotus segetalis (Brot) Ser.] were grown for a complete life cycle with and without saline (NaCl treatment of CE=15 dS m⁻¹). Growth and partitioning analyses were performed. Sequential harvests (every 15 d) during the life cycle, and separation of plant material into roots, stems, petioles, leaves and reproductive structures were carried out Salt treatment reduced growth during the early and middle stages of the life of the plant, but did not significantly affect RGR in the reproductive phase. The root–shoot allometric coefficient of salinized plants in the generative phase decreased more than in control plants. We suggest that salinity-induced growth reduction in M. segetalis was primarily a result of a lower unit leaf rate (ULR) despite an increased leaf area ratio (LAR). Earlier flowering, higher biomass allocation to shoot and greater reproductive investment, but similar relative growth rate (RGR), were some of the main characteristics of salt-stressed plants compared to controls during the reproductive phase, these apparently being associated with increased sink strength caused by developing flowers and fruits.     

Inhibition of tomato shoot growth by over‐irrigation is linked to nitrogen deficiency and ethylene

Although physiological effects of acute flooding have been well studied, chronic effects of suboptimal soil aeration caused by over‐irrigation of containerized plants have not, despite its likely commercial significance. By automatically scheduling irrigation according to soil moisture thresholds, effects of over‐irrigation on soil properties (oxygen concentration, temperature and moisture), leaf growth, gas exchange, phytohormone [abscisic acid (ABA) and ethylene] relations and nutrient status of tomato (Solanum lycopersicum Mill. cv. Ailsa Craig) were studied. Over‐irrigation slowly increased soil moisture and decreased soil oxygen concentration by 4%. Soil temperature was approximately 1°C lower in the over‐irrigated substrate. Over‐irrigating tomato plants for 2 weeks significantly reduced shoot height (by 25%) and fresh weight and total leaf area (by 60–70%) compared with well‐drained plants. Over‐irrigation did not alter stomatal conductance, leaf water potential or foliar ABA concentrations, suggesting that growth inhibition was not hydraulically regulated or dependent on stomatal closure or changes in ABA. However, over‐irrigation significantly increased foliar ethylene emission. Ethylene seemed to inhibit growth, as the partially ethylene‐insensitive genotype Never ripe (Nr) was much less sensitive to over‐irrigation than the wild type. Over‐irrigation induced significant foliar nitrogen deficiency and daily supplementation of small volumes of 10 mM Ca(NO₃)₂ to over‐irrigated soil restored foliar nitrogen concentrations, ethylene emission and shoot fresh weight of over‐irrigated plants to control levels. Thus reduced nitrogen uptake plays an important role in inhibiting growth of over‐irrigated plants, in part by stimulating foliar ethylene emission.     

<i>In Vitro</i> Propagation,Isolation and Expression Studies of <i>Suaeda edulis</i> Genes Involved in the Osmoprotectants Biosynthesis

Halophytes are an excellent choice for the study of genes conferring salt tolerance to salt-sensitive plants and, they are suitable for reclamation and remediation of saline soil. We develop an in vitro plant propagation protocol and studies of genes involved with GB and Pro biosynthesis in Suaeda edulis. Axillary buds were used as explants and cultured in different treatments on Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of plant growth regulators. The highest number of multiple shoots was on MS medium containing 1 mg/L Benzyladenine (BA) and / or 2 g/L activated carbon with 5.5 ± 06 shoots per explant. The identification and expression analysis of genes involved in glycine betaine (GB) biosynthesis were S-adenosylmethionine synthetase (SAMS), choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH), and for proline (Pro) was pyrroline 5-carboxylate synthetase (P5CS). These sequences shared 90–95% of identity with others plant homologous in public databases. The amino acids sequence analysis showed that all these peptides contain some of the conserved motifs of those kinds of enzymes. The qRT-PCR analysis revealed a higher expression of SeBADH, SeCMO, and, SeP5CS genes in the roots and leaves from plants collected in the field in contrast with from in vitro plants. However, the expression level of SeSAMS was higher only in the leaves of plants collected in the field when compared to those cultivated in vitro.