Effect of arbuscular mycorrhizal fungi on growth,mineral nutrition,antioxidant enzymes activity and fruit yield of tomato grown under salinity stress

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by arbuscular mycorrhizal fungi Glomus mosseae. Tomato (Lycopersicon esculentum L. cv. Zhongzha105) plants were cultivated in soil with 0, 50 and 100 mM NaCl. Mycorrhization alleviated salt induced reduction of root colonization, growth, leaf area, chlorophyll content, fruit fresh weight and fruit yield. The concentrations of P and K were higher in AM compared with nonAM plants grown under nonsaline and saline conditions. Na concentration was lower in AM than nonAM plants grown under nonsaline and saline conditions. AMF colonization was accompanied by an enhancement of activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in leaves of both salt-affected and control plants. In addition, inoculation with AMF caused reduction in MDA content in comparison to salinized plants, indicating lower oxidative damage in the colonized plants.     

The influence of NaCl salinity on growth,yield and fruit quality of strawberry cvs. ‘Elsanta’ and ‘Korona’

In a 2-year field study, strawberry cvs. ‘Elsanta’ and ‘Korona’ were exposed to three different levels of NaCl salinity supplied as aqueous solutions characterised by electrical conductivities of 0.3 dS/m, 2.6 dS/m, and 5.1 dS/m. Salinity in the rhizosphere reduced plant growth by up to 44% in ‘Korona’ and 90% in ‘Elsanta’. A rather distinct cultivar difference represented the reduction in leaf area per plant of 85% in the second year of experiment in ‘Elsanta’ compared to 29% in ‘Korona’. Strawberry can be regarded as a Na⁺ excluder, because Na⁺ content of both strawberry cultivars remained below 3 mg g⁻¹ dry mass at all salinity levels. Cl⁻ content increased considerably, up to 70 mg g⁻¹ dry mass in ‘Korona’ and 80 mg g⁻¹ dry mass in ‘Elsanta’ plants. ‘Korona’ retained most of its Cl⁻ in roots and crowns, whereas in ‘Elsanta’ the maximum was detected in petioles. ‘Korona’ was able to accumulate up to 33% higher Cl⁻ content in the roots than ‘Elsanta’. Macronutrient deficiency due to NaCl salinity was not observed and in comparison to ‘Elsanta’, higher Cl⁻ content in roots of ‘Korona’ did not coincide with an impairment of macronutrient uptake. Salinity stress reduced fruit yield by up to 27% in ‘Korona’ and 64% in ‘Elsanta’. Fruit quality, characterised as taste, aroma, and texture by a consumer-type panel, decreased by more than 24% in ‘Elsanta’, but in ‘Korona’ differences were insignificant. Total soluble solids (Brix) and the ratio Brix/TA (TA, titratable acid) decreased significantly by about 20% in ‘Korona’ and 35% in ‘Elsanta’. To summarise, the ability of ‘Korona’ to retain Cl⁻ in the root system more effectively than ‘Elsanta’ resulted not only in a 41% lower leaf Cl⁻ content at the highest salinity level and a better growth under NaCl stress, but also in a relatively higher fruit yield and fruit quality.     

Effects of cultural cycles and nutrient solutions on plant growth,yield and fruit quality of alpine strawberry (Fragaria vesca L.) grown in hydroponics

Alpine strawberry (Fragaria vesca L.) was grown in hydroponics with the nutrient film technique, in order to evaluate the effects of four buffer concentrations (1.3, 1.6, 1.9, 2.2 mS cm⁻¹) and two cultural cycles (summer-spring versus autumn-spring) in terms of growth, yield and fruit quality (dry and optical residues, sugars, acids, antioxidants, mineral composition). The longer summer-spring cycle gave a correspondingly higher yield than the autumn-spring one. The 1.3 mS cm⁻¹ nutrient solution was the most effective in terms of overall and spring production. However, the autumn and winter yields were not affected by the buffer EC. Fruit quality did not change with the cultural cycle, but the berries harvested in the spring had higher vitamin C and sucrose content and lower nitrate content compared with berries picked up in the winter. Fruit quality was also improved when the nutrient solution concentration increased. From the productive point of view, the cultural cycle choice should be made considering that 71% of the yield of the more productive summer-spring cycle derived from the spring harvest. Moreover, as regards the nutrient solution strength, 1.3 mS cm⁻¹ EC should be preferred during the spring season, whereas the 2.2 mS cm⁻¹ EC proved to be best in the winter in terms of fruit quality.     

Impact of exogenous salicylic acid on the growth,antioxidant activity and physiology of carrot plants subjected to combined salinity and boron toxicity

Previous studies have shown that salicylic acid (SA) plays a role in the response of plants to salt and osmotic stresses. Therefore, an experiment was conducted to investigate the impact of exogenous salicylic acid on the growth, physiology and antioxidant activity of carrot (Daucus carota L. cv. Nantes) grown under combined stress of salinity and boron toxicity. The treatments consisted of salt (control, NaCl, and Na₂SO₄), boron (−B: 0 and +B: 25 mg B kg⁻¹) and salicylic acid (−SA: 0 and +SA: 0.5 mmol SA kg⁻¹). The diameter of the storage root was increased by NaCl salinity in the absence of B toxicity, however, it was increased by Na₂SO₄ salinity under B toxicity. For the storage root yield, NaCl salinity was more toxic than Na₂SO₄ salinity. With its role in plant growth regulation, SA application positively affected the storage root dry weight, S concentration, carotenoids and anthocyanin content and increased the total antioxidant activity (AA) of the shoot and storage root. SA application regulated proline and toxic ion (B, Cl) accumulation in the storage root and shoot. This study reports the long term effects of SA under stress conditions and reveals that SA was not as effective as in alleviating abiotic stress as reported in the literature conducted with short-term studies. That means long-term effects of SA would be significantly different from its short-term effects.     

Effect of 24-epibrassinolide on growth,yield, antioxidant system and cadmium content of bean (Phaseolus vulgaris L.) plants under salinity and cadmium stress

The plants of Phaseolus vulgaris L. were grown in the presence of NaCl and/or CdCl₂ and were sprayed with 5 μM of 24-epibrassinolide (EBL) at 15 days after transplanting (DAT) and were sampled at 30 DAT and at the end of experiment. The plants exposed to NaCl and/or CdCl₂ exhibited a significant decline in growth, the level of pigment parameters, green pod yield and pod protein. However, the follow up treatment with EBL detoxified the stress generated by NaCl and/or CdCl₂ and significantly improved the above parameters. The NaCl and/or CdCl₂ increased electrolyte leakage, lipid peroxidation and plant Cd²⁺ content, and decreased the membrane stability index (MSI) and relative water content. However, the EBL treatment in absence of the stress improved the MSI and relative water content and minimized plant Cd²⁺ content but could not influence electrolyte leakage and lipid peroxidation. The antioxidative enzymes and the level of proline exhibited a significant increase in response to EBL as well as to NaCl and/or CdCl₂ stress.     

The effect of split-root salinity stress on tomato leaf expansion,fruit yield and quality

Summary

A crop-scale experiment between March and October 2000 investigated the effects of split-root salinity stress and rooting volume on the expansion of leaves, fruit yield and quality in two standard round fruited cultivars of tomato (Lycopersicon esculentumMill) Solairo and Espero, grown in rockwool. To implement the treatments, a split-root method was utilized whereby different levels of salinity (expressed as EC), adjusted by the addition of NaCl, was administered to two halves of a root system. The split-root high EC (2.8/8.0 dS m^–1) treatment enhanced fruit quality by increasing the concentrations of sugar, acid, total soluble solids and reducing the incidence of visual defects such as uneven ripening and gold-spot. Split-root high EC did however reduce leaf area that corresponded with low K concentration in the leaf tissue. The split-root method utilized doubled the rooting volume compared with the standard single rockwool slab, but this extra rooting capacity had no detectable effect on leaf expansion, yield or fruit quality. Although there was little impact on yield for ten weeks after the imposition of the high EC split-root treatment, mean reductions in weekly yield occurred thereafter and were of the order of 9 and 13% for ‘Solairo’ and ‘Espero’ respectively through to the end of the experiment. The fall in yield was due, in part, to a decrease in fruit size. Whilst water uptake was reduced it was unclear how the effects on leaf growth and fruit yield were mediated in the shoot. Possible processes that coordinate responses to root-zone salinity stress are discussed. The potential use of the split-root system in commercial production is considered.     

Influence of fruit load on dry matter and N-distribution in sweet pepper plants

The influence of fruit load on the leaf characteristics and on the distribution of dry matter (DM) and nitrogen (N) in sweet pepper (Capsicum annuum L., cv. Cornado) plants was investigated under Mediterranean glasshouse conditions during a winter–spring production cycle (from December till June). DM weight of all organs (roots, stems + petioles, leaves and fruits) and N content were determined throughout the growing cycle over a 3-week interval. The results showed that the cyclic fruit load pattern (production flushes) was associated with strong variations of N-leaf content on an area basis and specific leaf weight, SLW. On a whole plant scale, the value of SLW dramatically decreased (≈30%) with increasing fruit load; the reverse held true as long as the fruit dry weight remained low (<30 g pl⁻¹). The decline in SLW was coincident with a shift in distribution of DM and N in the plant, both preferentially diverted to the fruits. The time evolution of DM and N fractions in organs exhibited periodic fluctuations, with a duration close to the length of a fruit growth cycle (about 70 days, from anthesis to harvest). Linear relationships were found between the fraction of dry mass and N in fruits, and those of the other organs. The slope of these relationships was considered as an indicator of the response and sensitivity of the organ growth to an increase in fruit load. The root dry mass fraction was the most affected by increases in fruit load (slope of −0.75), while the N fraction in roots and in leaves was affected to a similar extent (slope of −0.50 and of −0.40, respectively). We conclude that, in the sweet pepper, the cyclic pattern of fruit load induces opposite cyclic patterns of dry matter and N content in the other aerial organs as well as in the roots, thereby reflecting close shoot–root coordination in the allocation of carbon and nitrogen resources among the organs. Finally, we discuss the possible implications that could derive from these findings for modelling dry matter partitioning in plants subjected to continuous fruit harvesting.     

几种秸秆基质对辣椒生长及果实品质的影响

菊芋是青海高原的特色经济作物,地上部秸秆生物量大,为解决其综合利用问题,将发酵完全的菊芋、小麦、油菜及玉米的秸秆复配羊粪、商品基质土、蛭石和珍珠岩作为辣椒的栽培基质,采用槽式无土栽培,通过对辣椒不同时期生长情况的监测来分析作物秸秆对辣椒生长、品质及产量的影响。结果表明,添加作物秸秆对辣椒生长、品质及产量都有正向影响,尤其是添加了菊芋秸秆的栽培基质在株高、茎粗、株幅等生长指标中都优于对照,果实的可溶性总糖、维生素C含量也都高于其他处理,有效增加了辣椒生物量,提升了果实品质,并且辣椒产量较对照增加了3%~5%。综合试验结果,添加菊芋秸秆可以提高辣椒的生物量、果实品质和产量。     

高温下丝瓜砧木对嫁接黄瓜生长、产量及果实品质的影响

为了探究嫁接对黄瓜生长、产量及果实品质的影响,将荷兰型短黄瓜‘春秋王2号’嫁接到‘五叶香’丝瓜砧木上,对植株田间生长、发病情况及后期产量、品质进行了测定。结果表明,移栽后的丝瓜嫁接苗在各时期测定的植株高度、茎粗度、叶片数、叶面积及净光合速率(Pn)都大于黄瓜自根砧嫁接苗,且病毒病发病率低,始花期比自根砧嫁接苗提早6 d,早期产量也较自根砧嫁接苗高,但后期增产不明显;果实中维生素C及可溶性蛋白含量与自根砧嫁接苗相差不大,可溶性糖含量显著降低,但游离氨基酸含量显著升高,说明以‘五叶香‘丝瓜为砧木嫁接黄瓜,在一定程度上能提高高温季节下黄瓜的产量,且该嫁接使得果实中游离氨基酸含量增加,提高了黄瓜的营养价值。     

The effects of nutrient solution sterilization on the growth and yield of hydroponically grown lettuce

Two methods of removing bacteria from hydroponic nutrient solution [ultraviolet (UV) radiation and submicronic filter] were evaluated for efficiency and for their effects on lettuce (Lactuca sativa L.) production. Both methods were effective in removing bacteria; but, at high intensity, the ultraviolet sterilizer significantly inhibited the production of plants grown in the treated solution. Bacterial removal by lower intensity UV or a submicronic filter seemed to promote plant growth slightly, but showed no consistent, statistically significant effect.     

Assessment of tolerance to NaCl salinity of five olive cultivars,based on growth characteristics and Na and Cl exclusion mechanisms

Changes caused by NaCl-induced salinity on several growth parameters and ions accumulation have been measured in five olive (Olea europaea L.) cultivars (‘Chemlali’, ‘Chetoui’, ‘Koroneiki’, ‘Arbequina I18’, and ‘Arbosana I43’) growing in a greenhouse in nutrient solution pot experiment. One-year-old plants were transplanted to sand–perlite (1:1) culture, and were irrigated with half-strength Hoagland nutrient solution containing NaCl at various levels (0.5, 50, 100 and 200 mM). Salinity induced significant decrease in growth parameters, but to a different extent in each cultivar. Leaf growth and total leaf area per plant were significantly affected by all salinity treatments in all studied cultivars, being ‘Arbequina I18’ the most sensitive cultivar. Leaf drop phenomenon was observed from 60 days after salt application at high salinity treatments, mainly in Arbequina I18. Contrary to leaf area, leaf thickness increased progressively during the experiment. ‘Chemlali’ developed thicker leaves at the two highest salinity treatments when compared to the other cultivars. Na⁺ and Cl⁻ concentrations were higher in roots than in shoots and leaves in most of the cultivars investigated. The effectiveness of Na⁺ exclusion mechanism in the roots differed significantly among studied cultivars, working effectively in ‘Chemlali’ (by inhibiting translocation of Na⁺ to the aerial part) and being much less efficient in ‘Arbequina I18’. Furthermore, leaf abscission can be considered as an additional tolerance mechanism of olive cultivars allowing the elimination of leaves that had accumulated Na⁺ and Cl⁻ ions. Tolerance to salinity stress was as follows: ‘Chemlali’ > ‘Chetoui’ > ‘Arbosana I43’ > ‘Koroneiki’ > ‘Arbequina I18’. This order of salt tolerance was indicated by lower reduction in plant growth parameters (shoot elongation, trunk diameter, total plant dry weight, internodes length, and total leaf area), the increase of leaf thickness, and by the effectiveness of the exclusion mechanism of Na⁺ and Cl⁻ in the root system.     

Effect of three Greek arbuscular mycorrhizal fungi in improving the growth,nutrient concentration,and production of essential oils of oregano and mint plants

Arbuscular mycorrhizal fungi have been widely used in agriculture to improve the cultivation of many crops. One of the aims of this study was the isolation and molecular identification of arbuscular mycorrhizal fungi isolated from mountain areas of Northern Greece (Ritini Pieria, Elatochori Pieria, Ambelakia Ossa). Only three isolates were obtained; two of Glomus etunicatum and one of G. lamellosum. The second objective of this study was to investigate the effect of these arbuscular mycorrhizal fungi on the concentration of macro- and micronutrients in tissues, the quantity and quality of essential oils and the growth of oregano and mint plants (two widely used aromatic plants in Greece). It was found that mycorrhizal oregano and mint plants had a higher content of essential oils and nutrient elements, and grew better than non-mycorrhizal plants. In addition, the composition of the essential oil in mycorrhizal plants differed from the oil of non-mycorrhizal plants. These results suggest that the use of mycorrhizal fungi may allow plant growth in low fertility soils, reduce fertilizer inputs and increase aromatic plant production of essential oils, They also indicate that it may be possible to use mycorrhizae to affect the quality of the essential oil produced.     

The influence of growing season on fruit yield and quality of greenhouse melon (Cucumis melo L.) grown in nutrient film technique in a Mediterranean climate

Summary

The influence of growing season on some physiological and biochemical variates related to fruit yield and quality was investigated in melon (Cucumis melo L.) plants cultivated in nutrient film technique in a greenhouse located at Pisa, Central Italy, from mid-March to mid-June, or from mid-July to mid-September. Compared with spring, the plants grown in summer exhibited faster growth and development, but produced fewer fruits of larger size and poorer quality due to reduced sucrose content. Growing season did not affect total leaf area, but dry-matter production and partitioning to the fruits was significantly lower in summer than in spring. Summer fruit ripened within 30–35 d after anthesis, about 14 d fewer than in spring. Higher average temperature was presumably responsible for earlier fruit maturation in summer, as in both seasons all melons were harvested after 450–500 degree-days (base temperature of 12°C) from anthesis. Fruit swelling did not account for the reduction of sucrose content in summer-grown fruits, which instead was due to shortage of photoassimilate supply and inadequate sucrose synthesis, as suggested by the rate of leaf gas exchange and the activity of sucrose phosphate synthase in the fruit flesh, as determined during the final stages of fruit development. Lower solar radiation was presumably responsible for the reduced leaf carbon assimilation in summer, as growing season did not affect leaf turgor, stomatal conductance, mineral status and chlorophyll content.     

The influence of drip irrigation or subirrigation on tomato grown in closed-loop substrate culture with saline water

In closed-loop soilless culture, one of the most relevant problems may be the accumulation in the recirculating nutrient solution of ions contained in irrigation water that are not or scarcely absorbed by the plants (e.g. Na, Cl) In order to verify the possibility to reduce the rate of recirculating water salinisation by means of subirrigation, an experiment was carried out in the spring of 2002 and 2004, with tomato plants (cv. Jama) grown in glasshouse and watered by conventional drip irrigation (D) or by subirrigation (trough bench system; S). The plants were cultivated in pots filled with a peat-perlite substrate for approximately 3 months and fed with complete nutrient solution, which was prepared with fresh water containing 10 mol m⁻³ NaCl; the nutrient solution in the collecting tank was replaced when the value of electrical conductivity (EC) exceeded 6.0 dS m⁻¹. Water and nutrient crop use, salt accumulation in the substrate, and fruit yield were monitored. In S culture, the composition and EC of the recirculating nutrient solution changed slightly, while in D treatment there was a fast water salinisation that made it necessary to flushed out the nutrient solution in six different occasions, with consequent loss of water and fertilisers. In S culture, the upward water movement in the substrate, coupled with selective mineral uptake by the roots, caused salinity build-up in the upper region of the substrate, which was associated with Na⁺ accumulation. No significant influence of irrigation methods on fruit yield and quality was observed. These findings suggest that subirrigation can be a tool to reduce the water consumption and nutrient runoff in closed-loop substrate culture of tomato conducted with saline water.     

Effect of phosphite fertilization on growth,yield and fruit composition of strawberries

Traditionally, phosphates (Pi, salts of phosphoric acid, H₃PO₄) have been used for plant fertilization, and phosphites (Phi, salts of phosphorous acid, H₃PO₃) have been used as fungicides. Nowadays several Phi fertilizers are available in the EU market despite the fact that in research trials Phi has often had a negative influence on plant growth. The objective of this study was to elucidate the effect of a Phi fertilizer on plant growth, yield and fruit composition of strawberries (Fragaria × ananassa Duch.). Experiments were carried out with ‘Polka’ frigo plants in South Estonia in 2005 and 2006. The number of leaves per plant, total and marketable yields, fruit size, fruit ascorbic acid content (AAC), soluble solids content (SSC), titratable acidity (TA), anthocyanins (ACY) and total antioxidant activity (TAA) were recorded.     

丛枝菌根真菌对温室黄瓜生长及产量品质的影响

以黄瓜为材料于温室盆栽条件下,研究丛枝菌根真菌(arbuscular mycorrhizas fungi,AMF)Glomous ver-siforme(GV)对黄瓜生长的影响。结果表明:苗期接种GV真菌后可提高黄瓜的株高,叶片中叶绿素a、叶绿素b、类胡萝卜素及可溶性糖含量;提高了黄瓜产量;黄瓜中总糖、干物质重量和维生素C、N、P、K、Zu、Cu等营养物质含量也有增加。     

Influence of sulfur supply,ammonium nitrate ratio,and arbuscular mycorrhizal colonization on growth and composition of Chinese chive

Tissue concentrations of phytochemicals formed by Allium species may be influenced by plant nutrient supply or rhizosphere microorganism activity. To test these relations, three plant nutritional factors were varied in two experiments with Chinese chive [Allium tuberosum]: (a) increasing sulfur concentrations in the substrate, (b) two ratios of ammonium to nitrate in supply, and (c) inoculation with arbuscular mycorrhizal (AM) fungi. Shoot dry weight, nutrient composition (nitrate, N, P, S), and organosulfur compounds (measured indirectly as pyruvic acid) were determined.     

Effect of Glomus mosseae and Entrophospora colombiana on plant growth,production, and fruit quality of ‘Maradol’ papaya (Carica papaya L.)

The effect of inoculating ‘Maradol’ papaya plants with arbuscular mycorrhizal fungi (AMF) Glomus mosseae (GM) and Entrophospora colombiana (EC) was assessed. The results showed that both mycorrhizae species increased the number of fruits and yield in papaya plants by 41.9 and 105.2% for GM and 22.1 and 44.1% for EC, respectively, with respect to control plants. GM significantly increased plant height. Sugar content, firmness, color (°Hue), and ripening process of mycorrhized plant fruits were similar to those of the control. Weight loss of mycorrhized plant fruits was considerably less than that of the control. Inoculation of papaya with AMF is recommended, particularly with GM since it increases yield, and fruit weight (45.1%), furthermore, it reduced fruit weight loss during ripening.     

Growth,yield and fruit quality of ‘Marisol’ clementine grown on four rootstocks in Egypt

To evaluate the most appropriate rootstocks for mandarin production in Egypt, vegetative growth, yield and fruit quality of ‘Marisol’ clementine (as newly introduced cultivar in Egypt) grafted on Sour orange (the common rootstock), Cleopatra mandarin, Carrizo citrange and ‘Swingle’ citrumelo were evaluated under the Egyptian conditions during 2004/2005 and 2005/2006 seasons. Trees were grown in a private farm at ‘Wady El-Mullak’ region, Ismailia Governorate (Latitude, 30°36′ N; longitude, 32°14′ E; Altitude, 10 m above sea level).     

The combined effects of salinity and excess boron on mineral ion relations in broccoli

Two plant stress factors, salinity and high levels of boron, often co-occur in natural and agricultural environments. Many investigations have been conducted to document the influence of the combined stresses on crop growth and yield. Only limited information, however, is available concerning the combined effects of the two stresses on mineral ion uptake and partitioning to shoot organs and tissues. Data for this study were obtained from an experiment conducted in greenhouse sand cultures with two water types: (1) a chloride-dominated system, and (2) sulfate-dominated waters characteristic of those present in the San Joaquin Valley of California. Each saline composition treatment was tested at three salinity levels (2, 12, 18 dS m⁻¹) and three B concentrations (0.046, 1.11, 2.22 mM; 0.5, 12, 24 mg L⁻¹). The gradient in B distribution in individual leaves sampled midseason was steep, with less boron accumulating in petioles than in the blades. The highest B concentrations (>100 mmol B kg⁻¹ dry weight) were found in leaf margins of plants grown in the low salinity-high boron treatments. These leaves were cupped upward, an unusual visual symptom characteristic of B toxicity. At final harvest, concentrations of B, Ca, Mg, Na, K, and Cl were highest in the oldest leaves on the broccoli shoots, decreasing acropetally to the heads. Total-P, however, was highest in broccoli heads, decreasing in the older tissues. Leaf-B accumulation was more closely related to salinity rather than to the concentration of Cl in the irrigation waters. Analysis of variance indicated that substrate B had little effect on Cl accumulation in salt-stressed broccoli leaves regardless of water type. No clear cut relationships were evident that would explain the reciprocal effects of B and Cl on crop yields.