Rida A. Shibli

TOMATO ROOT AND SHOOT RESPONSES TO SALT STRESS UNDER DIFFERENT LEVELS OF PHOSPHORUS NUTRITION

Abstract Crops differ in their ability to grow under saline conditions and their responses are quite variable and not fully understood. This study was conducted to evaluate the root and shoot responses of tomato to salt stress conditions under different levels of phosphorus (P) nutrition. Tomato seedlings (cv Riogrande) were grown in 500 mL glass jars containing Hoaglands solutions which were salinized by four levels of NaCl salt (0,50,100, and 150 mM NaCl) and/or enriched with three P levels (0.5,1, and 2 mM P) making nine combination treatments. Plants were harvested at the vegetative growth stage and data were collected for root and shoot characteristics. The results indicate that increasing salinity stress was accompanied by significant reductions in shoot weight, plant height, number of leaves per plant, and a significant increase in leaf osmotic potential and peroxidase activity regardless of the level of P supplied. Both root length and root surface area per plant were decreased significantly unde...

Effects of Arbuscular Mycorrhizal Fungi and Phosphorus Fertilization on Growth and Nutrient Uptake of Barley Grown on Soils with Different Levels of Salts

Abstract Greenhouse experiment was conducted to evaluate the effect of arbuscular mycorrhizal fungi (AMF) on plant growth, and nutrient uptake in saline soils with different salt and phosphorus (P) levels. The following treatments were included in this experiment: (i) Soil A, with salt level of 16.6 dS m−1 and P level of 8.4 mg kg−1; (ii) Soil B, with salt level of 6.2 dS m−1 and P level of 17.5 mg kg−1; and (iii) Soil C, with salt level of 2.4 dS m−1 and P level of 6.5 mg kg−1. Soils received no (control) or 25 mg P kg−1 soil as triple super phosphate and were either not inoculated (control) or inoculated with a mixture of AM (AM1) and/or with Glomus intraradices (AM2). All pots were amended with 125 mg N kg−1 soil as ammonium sulfate. Barley (Hordeum vulgar L., cv. “ACSAD 6”) was grown for five weeks. Plants grown on highly saline soils were severely affected where the dry weight was significantly lower than plants growing on moderately and low saline soils. The tiller number and the plant height were also lower under highly saline condition. The reduced plant growth under highly saline soils is mainly attributed to the negative effect of the high osmotic potential of the soil solution of the highly saline soils which tend to reduce the nutrient and water uptake as well as reduce the plant root growth. Both the application of P fertilizers and the soil inoculation with either inoculum mixture or G. intraradices increased the dry weight and the height of the plants but not the tiller number. The positive effect of P application on plant growth was similar to the effect of AM inoculation. Phosphorus concentration in the plants was higher in the mycorrhizal plant compared to the non mycorrhizal ones when P was not added. On the other hand, the addition of P increased the P concentration in the plants of the non mycorrhizal plants to as high as that of the mycorrhizal plants. Iron (Fe) and zinc (Zn) uptake increased with AM inoculation. The addition of P had a positive effect on micronutrient uptake in soil with low level of soil P, but had a negative effect in soil with high level of soil P. Micronutrient uptake decreases with increasing soil salinity level. Inoculation with AMF decreases sodium (Na) concentration in plants grown in soil of the highest salinity level but had no effect when plants were grown in soil with moderate or low salinity level. The potassium (K) concentration was not affected by any treatment while the K/Na ratio was increased by AM inoculation only when plant were grown in soil of the highest salinity level.

Somatic embryogenesis in the endemic black iris.

Somatic embryogenesis was achieved from callus, cell suspension and protoplast culture systems in the endemic black iris (Iris nigricans). Subculture of friable callus fragments on embryogenesis induction medium (EIM) containing 4.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.5 μM kinetin, 4.5 μM 1-naphthaleneacetic acid (NAA) and 300 mg l-1 proline in the dark was necessary before transfer to regeneration medium (RM). Regeneration was studied by transferring friable callus fragments from EIM to RM containing (0.0, 4.5, 9.0, 13.5 μM) of either 6-benzyladenine (BA), 2-isopentenyladenine (2iP), zeatin or thidiazuron (TDZ) in combination with 0.49 μM indole-3-butyric acid (IBA), 0.45 μM 2,4-D. Maximum embryogenesis was obtained at 4.5 μM BA while zeatin and TDZ were not effective and embryogenesis did not occur with these treatments. Sucrose at 0.2 M was more effective for embryogenesis when compared to glucose or fructose. Growing cells in suspension culture on EIM containing 4.5 μM 2,4-D in combination with 0.2 M sucrose for four weeks and transferring cells to RM (containing 4.5 μM BA) gave significant embryogenesis with maximum number of embryos (3568 embryos/g cells). Using 4.5 μM 2,4-D in protoplast culture was necessary for the best protoplast division and colony formation. In all experiments, embryos developed on RM were transferred to hormone-free medium (HFM) and 90% converted to rooted plantlets. Produced plantlets gave 95% survival ex vitro. Plantlets developed to whole plants in the greenhouse and flowered.

Osmotic adjustment and growth responses of three Chrysanthemum morifolium Ramat. cultivars to osmotic stress induced in vitro

Abstract In vitro‐grown Chrysanthemum morifolium Ramat. cultivars Bright Golden Anne, Deep Luv, and Lucido were exposed to elevated mannitol, sucrose, or sorbitol concentrations to see if their response to this osmotic stress mimics that of in vivo plants enduring water deficit. The relative efficacy of the three osmotic agents at manifesting a response was also evaluated. Tissue osmolarity paralleled media mannitol and sorbitol concentration for all three cultivars. Shoot growth correspondingly decreased with increased osmolarity applied during the rooting phase. These responses generally resembled those of water‐stressed greenhouse plants. The degree of response varied with cultivar; ‘Lucido’ was the most sensitive and ‘Bright Golden Anne’ the least. Sucrose (metabolized by the plants) failed to elicit consistent osmotic stress symptoms; instead it enhanced both shoot and root growth. In vitro stress‐induced symptoms were produced in both proliferation and rooting stages, but consistent shoot growth red...

Phosphorus regulates osmotic potential and growth of African violet under in vitro-induced water deficit.

Abstract Interactive effects of phosphorus (P) with in vitro‐induced water deficit (using sorbitol and mannitol) were studied on African violet (Saintpaulia ionantha) whole‐plant microculture. Sorbitol and mannitol significantly reduced (more negative) the cell sap osmotic potential. Increased P was very effective in increasing (less negative) the osmotic potential of cell sap under the imposed water deficit treatments. On the other hand, induced water deficit significantly reduced shoot growth (shoot height and dry mass), and root number and length, whereas P mitigated these adverse effects and improved shoot and root growth. Cultures exposed to water deficit at 150mM sorbitol and mannitol experienced some physiological disorders (about 10% shoot tip browning, 15% stem basal‐end browning) and 20% chlorosis. Physiological disorders and chlorosis were totally mitigated with increased P to 1.0 or 2.0 mM. Phosphorus concentration in shoot tissues was decreased with water deficit in the medium and enhanced by elevated P in the medium. Ex vitro survival percentages increased in plantlets that experienced in vitro water deficit with sorbitol and mannitol at 50 to 100 mM and P at 1.0 to 2.0 mM. We conclude that P is a key factor to regulate cell osmotic potential and growth under in vitro induced water deficit. On the other hand, microculture level is a very effective alternative for the study of plant response and tolerance to water deficit and its interaction with nutrient availability in the root zone.

Influence of Sodium Chloride Salt Stress on Growth and Nutrient Acquisition of Sour Orange In Vitro

Abstract Growth and nutrient acquisition in sour orange (Citrus aurantium L.) were studied under salt stress in vitro. Microshoots were transferred to Murashige and Skoog (MS) solid proliferation media containing 8.9 µM BA (6‐Benzyladenine) and 0.5 µM NAA (naphthaline acetic acid). Salinity was induced by incorporating different concentrations [0.0 (control), 50, 100, 150, 200, or 300 mM] of sodium chloride (NaCl) to the culture media. Microshoots were exposed to direct or gradual salinity shock. Slight reduction was obtained in growth (shoot length, shoot number, leaf number, and dry weight) when microshoots were directly exposed to NaCl stress from 0.0 to 150 mM. At 200 and 300 mM NaCl, growth parameters were adversly affected and microshoots died thereafter. Gradual NaCl shock was studied by transferring microshoots sequentialy every week to different NaCl concentraions (0.0, 50, 100, 150, 200, or 300 mM). Growth was monitored at each concentration until the end of the last week of incubation at 300 mM NaCl. Growth (shoot length, shoot number or leaf number, and dry weight) generally decreased with elevated salinity level, but was less impaired than the direct shock. The percentage of shoot content of phosphorus (P), potassium (K), and iron (Fe) in the direct Nail shock experiment were reduced with elevated salinity level. This reduction was less in the gradual shock treatments. Sodium Chloride level strongly reduced Fe acquisition under both direct and gradual salinity stress. Tissue contents of sodium (Na), zinc (Zn), and manganese (Mn) were increased with the imposed salinity treatments in both experiments.

CRYOPRESERVATION OF AFRICAN VIOLET (SAINTPAULIA IONANTHA WENDL.) SHOOT TIPS

SummaryCryopreservation of African violet via encapsulation-dehydration, vitrification, and encapsulation-vitrification of shoot tips was evaluated. Encapsulation-dehydration, pretreatment of shoot tips with 0.3 M sucrose for 2 d followed by air dehydration for 2 and 4 h resulted in complete survival and 75% regrowth, respectively. Dehydration of encapsulated shoot tips with silica gel for 1 h resulted in 80% survival but only 30% regrowth. Higher viability of shoot tips was obtained when using a step-wise dehydration of the material rather than direct exposure to 100% plant vitrification solution (PVS2). Complete survival and 90% regrowth were achieved with a four-step dehydration with PVS2 at 25°C for 20 min prior to freezing. The use of 2M glycerol plus 0.4M sucrose or 10% dimethyl sulfoxide (DMSO) plus 0.5M sucrose as a cryoprotectant resulted in 55% survival of shoots. The greatest survival (80–100%) and regrowth (80%) was obtained when shoot tips were cryoprotected with 10% DMSO plus 0.5M sucrose or 5% DMSO plus 0.75M sucrose followed by dehydration with 100% PVS2. Shoot tips cryoprotected with 2M glycerol plus 0.4M sucrose for 20 min exhibited complete survival (100%) and the highest regrowth (55%). In encapsulation-vitrification, dehydration of encapsulated and cryoprotected shoot tips with 100% PVS2 at 25°C for 5 min resulted in 85% survival and 80% regrowth.

Metal concentrations, growth, and yield of potato produced from In Vitro plantlets or microtubers and grown in municipal solid‐waste‐amended substrates

Abstract In vitro plantlets or microtubers (in vitro produced tubers) of ‘Spunta’ potato (Solanum tuberosum L.) were planted in a 3 soil: 2 peat moss: 1 sand substrate (by volume) amended with municipal solid waste (MS W) compost at 0, 10, 20, or 30 g 4‐1 L pot. Three months later, plant growth and tuber yield were evaluated and concentrations of shoot and tuber tin (Sn), arsenic (As), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), manganese (Mn), cadmium (Cd), and iron (Fe) were determined. Amending with MSW resulted in significant increases in concentrations of all tested metals in the substrate. Number of proliferated shoots of plants started from rooted plantlets was greatest at 10 g pot‐1 MSW, whereas shoot weight of plants started from microtubers was greatest at 10 and 20 g pot‐1 MSW. Tuber yield of plants started from rooted plantlets or microtubers was greatest at 10 or 30 g pot‐1 MSW, respectively. In all instances, amending with MSW at 30 g pot‐1 resulted in significant increases in concentrat...

Effects of NaCl salinity on miniature dwarf tomato ‘Micro‐Tom’: II. Shoot and root growth responses, fruit production, and osmotic adjustment 1

Abstract The growth and production of miniature dwarf tomato selection Lycopersicon esculentum ’Micro‐Tom’ plants grown from seedling to harvest in solution batph culture’ at four different NaCl salinity levels (2.4 [control, no NaCl], 7.6, 12.8, or 18 dS‐m‐1 solution conductivities) was monitored. Incremental reductions in canopy extent and shoot area of ‘Micro‐Tom’ were observed with increasing solution NaCl level. Root growth and shoot height were somewhat less responsive to imposed salinity. Fruit number, fruit size, and leaf tissue osmotic potential decreased as NaCl concentration increased. Fruit yield was highly correlated with total canopy and shoot area, but not with tissue osmotic or total water potential. ‘Micro‐Tom’ plants survived and continued fruit production at higher salinity levels despite reduced canopy growth. Treatment effects on vegetative growth and fruit production became more pronounced later in the growth cycle.

INCREASED PHOSPHORUS MITIGATES THE ADVERSE EFFECTS OF SALINITY IN TISSUE CULTURE

Interactive effects of increased phosphorus (P) with salinity were studied at the microculture level of African violet (Saintpaulia ionantha). Increased P from 0.5 to 2.0 mM in the medium was very effective to mitigate the adverse effects of increased NaCl salinity (0.0, 50, 75, 100 mM). Growth (shoot height, and dry mass) was significantly reduced with increased salinity, whereas increasing P improved growth with elevated salt concentrations. Leaf osmolarity was decreased (more negative) with salinity effect and it was increased (less negative) by P treatments. Percent ash was increased with salinity and it was not highly affected by P. Root number and root length were significantly reduced with increased salinity and improved with increased P. The percentage of shoot content of nitrogen (N), P, calcium (Ca), potassium (K), and magnesium (Mg) were reduced with elevated salinity level and this reduction was less as P concentration increased in the medium. Sodium (Na) was significantly increased with imposed salinity and its uptake was reduced with increased P level. Zinc (Zn), manganese (Mn), and copper (Cu) uptake were increased with elevated salinity level and reduced with elevated P level in the media. Increased NaCl level strongly reduced Fe uptake and P was very effective in increasing iron (Fe) uptake. An overall increased P was very effective in regulating macro and micronutrients uptake, counteracting the increased salinity adverse effects. We can conclude that P is a key element for studying the physiological responses of different plant species to salinity. Also in vitro cultures (a rigorously controlled system) could work as an efficient alternative for the study of salinity.