The effectiveness of grafting to improve salt tolerance in tomato when an ‘excluder’ genotype is used as scion

If the main effect of long-term exposure of tomato plants to salinity is the accumulation of toxic concentrations of Na⁺ and Cl⁻ in the leaves, then the selection of ‘excluder’ rootstocks should increase tolerance to salinity in grafted tomato plants, independently of the genotype used as the scion. The question addressed in this study is whether shoot genotypes with an ‘excluder’ character are able to increase their salt tolerance when grafted onto rootstocks of the same characteristics. Moneymaker (with excluder character) was grafted onto two root genotypes, Radja and Pera, selected for their very different ability to regulate the transport of saline ions to the shoot over time. Grafting onto either Pera or Radja improved fruit yield compared to the self-grafted plants of Moneymaker (M/M) when the plants were grown at 50 mM NaCl, whereas there was no effect of either rootstock or of grafting per se (M/M) on fruit yield in the absence of or at 25 mM NaCl. The relationship between the salt responses to mid- and long-term depended on the stress level; after 27 d of 150 mM NaCl treatment, both graft combinations enhanced similarly their salt tolerances as did in the long-term experiment. Moreover, the tolerance induced by rootstock was related to the low rates of saline ion accumulation in their leaves. However, the positive effect of rootstock was only observed with rootstock Pera when the grafted plants were grown at 50 mM NaCl (the same salt level used in the long-term experiment) for 35 d. According to the physiological changes induced by rootstock in the leaves, the different salt responses seem to be due to the fact that the osmotic effect predominated on the toxic effect under these last conditions. Consequently, in order to select rootstocks care must be taken in the timing of any selection process: the stress level and length of exposure to salinity must be sufficient for the true differences in salt tolerance for toxicity to be shown. Taken together, these results show the effectiveness of grafting to enhance fruit yield in tomato and provide evidence that the positive effect induced by rootstock is related to the re-establishment of ionic homeostasis.     

Improving melon and cucumber photosynthetic activity, mineral composition, and growth performance under salinity stress by grafting onto Cucurbita hybrid rootstocks

The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ??P360??, and ??PS1313??, respectively. Plants were grown hydroponically and supplied with two nutrient solutions ?? a nonsalinized control and a salinized solution which contained 40 mmol L^?1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the P _N and g _s reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na⁺ and Cl^? in the leaf tissue and P _N. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and P _N. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance.     

Grafting raises the salt tolerance of tomato through limiting the transport of sodium and chloride to the shoot

With the aim of determining whether grafting could improve salinity tolerance of tomato (Lycopersicon esculentum Mill.), and what characteristics of the rootstock were required to increase the salt tolerance of the shoot, a commercial tomato hybrid (cv. Jaguar) was grafted onto the roots of several tomato genotypes with different potentials to exclude saline ions. The rootstock effect was assessed by growing plants at different NaCl concentrations (0, 25, 50, and 75 mM NaCl) under greenhouse conditions, and by determining the fruit yield and the leaf physiological changes induced by the rootstock after 60 d and 90 d of salt treatment. The grafting process itself did not affect the fruit yield, as non-grafted plants of cv. Jaguar and those grafted onto their own root showed the same yield over time under non-saline conditions. However, grafting raised fruit yield in Jaguar on most rootstocks, although the positive effect induced by the rootstock was lower at 25 mM NaCl than at 50 and 75 mM NaCl. At these higher levels, the plants grafted onto Radja, Pera and the hybrid VolgogradskijxPera increased their yields by approximately 80%, with respect to the Jaguar plants. The tolerance induced by the rootstock in the shoot was related to ionic rather than osmotic stress caused by salinity, as the differential fruit yield responses among graft combinations were mainly related to the different abilities of rootstocks to regulate the transport of saline ions. This was corroborated by the high negative correlation found between fruit yield and the leaf Na(+) or Cl(-) concentrations in salt-treated plants after 90 d of salt treatment. In conclusion, grafting provides an alternative way to enhance salt tolerance, determined as fruit yield, in the tomato, and evidence is reported that the rootstock is able to reduce ionic stress.     

Investigation of the ameliorating effects of eggplant, datura, orange nightshade, local Iranian tobacco, and field tomato as rootstocks on alkali stress in tomato plants

Among the most important quality parameters of irrigation water used for greenhouse crops, alkalinity of water is considered critical due to its impact on soil or growing medium solution pH. In this study, plant growth, Fe content, photosynthetic pigment content, maximal quantum yield of PSII photochemistry (F_v/F_m), performance index (PI), leaf relative water content (LRWC), and soluble sugars concentration were investigated in nongrafted and grafted tomato (Lycopersicon esculentum Mill. cv. Red stone) plants onto five rootstocks of eggplant (Solanum melongena cv. Long purple), datura (Datura patula), orange nightshade (Solanum luteum Mill.), local Iranian tobacco (Nicotiana tabacum), and field tomato (Lycopersicon esculentum Mill. cv. Cal.jn3), exposed to 0, 5, and 10 mM NaHCO₃ concentrations, to determine whether grafting could improve alkalinity tolerance of tomato. Significant depression of leaf area, leaf and stem dry mass, shoot and root Fe content and LRWC under high NaHCO₃ level was observed in both grafted and ungrafted plants. The highest reduction in the shoot Fe content was observed at 10 mM sodium bicarbonate in control plants (greenhouse tomato). Moreover, at high HCO₃ ^? level, the highest percentage of LRWC reduction was also recorded in ungrafted plants. Values of F_v/F_m and PI decreased significantly at 5 and 10 mM NaHCO₃ irrespective of rootstock type. The present study revealed that soluble sugars content, photosynthetic pigments content, F_v/F_m and PI values in plants grafted onto datura rootstock were higher than those in nongrafted and rest of the grafted plants. Thus, the use of datura rootstock could provide a useful tool to improve alkalinity tolerance of tomato plants under NaHCO₃ stress.     

Effects of sulfur dioxide on the development of powdery mildew of cucumber

Environment is a major factor that does influence host parasite relationships. Air pollution caused by SO₂ may directly alter the environment around the plant and pathogen. It is hypothesised that plants may respond differently to foliar pathogens in air polluted environments. To test this hypothesis, effects of intermittent exposures of SO₂ at 143, 286 and 571 μg m⁻³ were investigated on the development of powdery mildew of cucumber (Cucumis sativa) caused by Sphaerotheca fuliginea, using pre-, post- and concomitant-inoculation exposures in closed-top chambers. Sulfur dioxide (except 143 μg m⁻³) and the fungus acting alone caused chlorosis and/or necrosis, and mildew colonies on leaves, respectively and both reduced the plant growth and yield of cucumber. Fungus colonization was relatively greater on the plants exposed to 143 μg SO₂ m⁻³, but at the higher concentrations, the colonies were greatly suppressed. Gas injury on fungus-infected plants was also less in the other treatments. Conidia of S. fuliginea collected from exposed plants varied in size. Conidial germination was considerably greater at 143 μg SO₂ m⁻³. This concentration also promoted germination of the conidia exposed on glass slides. Higher concentrations (286 and 571 μg m⁻³), however, suppressed the germination of conidia from exposed plants or exposed on glass slides. The number of fibrosin bodies declined at all the concentrations. Synergistic effects of 143 μg SO₂ m⁻³ and S. fuliginea were recorded on plant growth and yield of cucumber. Sulfur dioxide at 571 μg m⁻³ and powdery mildew infection had an antagonistic effect on plant growth.     

环境条件对黄瓜硅吸收分配和果面蜡粉形成的影响

为探明环境条件影响黄瓜果面蜡粉形成的机制,以‘山农5号’黄瓜为接穗,‘黄诚根2号’南瓜(去蜡粉能力强)和‘云南黒籽南瓜’(去蜡粉能力弱)为砧木进行嫁接,在日光温室不同栽培茬口(冬春茬和秋冬茬)下研究了硅吸收分配和果面蜡粉量差异,并在人工气候室内模拟不同季节环境条件[T₁:温度28 ℃/18 ℃(昼/夜),相对湿度55%/65%,光照强度600 μmol·m^-2·s^-1;T₂:温度22 ℃/12 ℃(昼/夜),相对湿度85%/95%,光照强度300 μmol·m^-2·s^-1],研究其对硅吸收分配和硅转运蛋白基因表达的影响。结果表明:日光温室栽培条件下,与秋冬茬相比,冬春茬黄瓜商品成熟果实表面蜡粉量显著增加,其中以‘云南黑籽南瓜’嫁接黄瓜受影响较大,自根黄瓜和‘黄诚根2号’嫁接黄瓜受影响较小;相同栽培季节,均以‘云南黑籽南瓜’嫁接黄瓜果面蜡粉量和器官硅含量最多,自根黄瓜次之,‘黄诚根2号’嫁接黄瓜最少。人工气候室内,T₁环境下黄瓜各器官硅含量、叶片和根系硅转运蛋白基因表达量均高于T₂;相同环境条件下,黄瓜各器官硅含量和叶片硅转运蛋白基因表达量均为‘云南黑籽南瓜’嫁接黄瓜＞自根黄瓜＞‘黄诚根2号’嫁接黄瓜。综上,环境条件改变了黄瓜植株对硅的吸收分配,进而影响果面蜡粉形成,适宜的环境条件有利于减少果面蜡粉量;高温、强光、低湿环境导致黄瓜果面蜡粉量增多,砧木对嫁接黄瓜硅吸收和果面蜡粉形成有显著影响。     

AMF与嫁接对西瓜连作土壤理化和微生物状况的影响

将嫁接京欣1号葫芦砧Lagenaria siceraria、京欣2号南瓜砧Cucurbita maxima × Cucurbita moschata和不嫁接的京欣4号西瓜自根苗定植于西瓜连作土壤中,接种丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）摩西管柄囊霉Funneliformis mosseae、变形球囊霉Glomus versiforme和根内根孢囊霉Rhizophagus intraradices处理,以不接种丛枝菌根真菌的处理为对照。结果表明,与对照相比所有处理均显著降低土壤全氮、速效磷、速效钾和有机质含量,但提高土壤pH。接种AMF并嫁接处理的>2mm和2-0.25mm粒级土壤团聚体含量显著高于单纯嫁接或只接种AMF或对照,所有处理的0.25-0.053mm与<0.053mm粒级土壤团聚体含量均显著低于对照。以接种AMF并嫁接处理的土壤细菌数量显著高于其他处理,而所有处理的真菌数量则显著低于对照,接种AMF并嫁接处理的放线菌数量一般高于对照。接种AMF并嫁接处理的土壤蔗糖酶、多酚氧化酶和脲酶活性显著高于对照。接种AMF结合嫁接改善连作土壤理化特性和土壤微生物区系的效应大于只嫁接或仅接种AMF的单一处理的。     

Root and stem hydraulic conductivity as determinants of growth potential in grafted trees of apple (Malus pumila Mill.)

The anatomy of the graft tissue between a rootstock and its shoot (scion) can provide a mechanistic explanation of the way dwarfing Malus rootstocks reduce shoot growth. Considerable xylem tissue disorganization may result in graft tissue having a low hydraulic conductivity (k(h)), relative to the scion stem. The graft may influence the movement of substances in the xylem such as ions, water and plant-growth-regulating hormones. Measurements were made on 3-year-old apple trees with a low-pressure flow system to determine k(h) of root and scion stem sections incorporating the graft tissue. A range of rootstocks was examined, with different abilities of dwarfing; both ungrafted and grafted with the same scion shoot cultivar. The results showed that the hydraulic conductivity (k(hroot)) of roots from dwarfing rootstocks was lower compared with semi-vigorous rootstocks, at least for the size class of root measured (1.5 mm diameter). Scion hydraulic conductivity (k(hs)) was linked to leaf area and also to the rootstock on to which it was grafted, i.e. hydraulic conductivity was greater for the scion stem on the semi-vigorous rootstock. Expressing conductivities relative to xylem cross-sectional areas (k(s)) did not remove these differences suggesting that there were anatomical changes induced by the rootstock. The calculated hydraulic conductivity of the graft tissue was found to be lower for grafted trees on dwarfing rootstocks compared to invigorating rootstocks. These observations are discussed in relation to the mechanism(s) by which rootstock influences shoot growth in grafted trees.     

嫁接对铜胁迫下黄瓜幼苗根系多胺代谢的影响

采用营养液栽培法,研究了嫁接(以黑籽南瓜为砧木)对铜胁迫下黄瓜幼苗根系活力及多胺代谢的影响.结果表明:铜胁迫下黄瓜幼苗根系活力下降,电解质渗漏率升高,而嫁接苗的变化幅度显著小于黄瓜自根苗;铜胁迫下黄瓜嫁接植株根系中除游离态腐胺(Put)含量显著低于自根苗外,结合态和束缚态Put、3种形态亚精胺(Spd)和精胺(Spm)含量均显著高于自根苗,嫁接苗根系中游离态Put含量及腐胺/多胺(Put/PAs)显著低于自根苗;铜胁迫下,嫁接苗根系精氨酸脱羧酶(ADC)、鸟氨酸脱羧酶(ODC)和S-腺苷蛋氨酸脱羧酶(SAMDC)活性高于自根苗,而二胺氧化酶(DAO)和多胺氧化酶(PAO)活性显著低于自根苗.表明嫁接黄瓜幼苗根系PAs的合成增加,降解减少,使PAs含量维持在较高水平,从而提高了黄瓜幼苗抗铜胁迫能力.     

Dithioerythritol (DTE) prevents inhibitory effects of triphenyltin (TPT) on the key enzymes of the human sex steroid hormone metabolism

Organotins are known to induce imposex (pseudohermaphroditism) in marine neogastropods and are suggested to act as specific endocrine disruptors, inhibiting the enzyme-mediated conversion of steroid hormones. Therefore, we investigated the in vitro effects of triphenyltin (TPT) on human 5-reductase type 2 (5-Re 2), cytochrome P450 aromatase (P450arom), 17β-hydroxysteroid dehydrogenase type 3 (17β-HSD 3), 3β-HSD type 2 and 17β-HSD type 1 activity. First, the present study demonstrates that significant amounts of TPT occurred in the blood of eight human volunteers (0.17–0.67 μg organotin cation/l, i.e. 0.49–1.92 nmol cation/l). Second, TPT showed variable inhibitory effects on all the enzymes investigated. The mean IC₅₀ values were 0.95 μM for 5-Re 2 (mean of n=4 experiments), 1.5 μM for P450arom (n=5), 4.0 μM for 3β-HSD 2 (n=1), 4.2 μM for 17β-HSD 3 (n=3) and 10.5 μM for 17β-HSD 1 (n=3). To exclude the possibility that the impacts of TPT are mediated by oxidizing essential thiol residues of the enzymes, the putative compensatory effects of the reducing agent dithioerythritol (DTE) were investigated. Co-incubation with DTE (n=3) resulted in dose-response prevention of the inhibitory effects of 100 μM deleterious TPT concentrations on 17β-HSD 3 (EC₅₀ value of 12.9 mM; mean of n=3 experiments), 3β-HSD 2 (0.90 mM; n=3), P450arom (0.91 mM; n=3) and 17β-HSD 1 (0.21 mM; n=3) activity. With these enzymes, the use of 10 mM DTE resulted in an at least 80% antagonistic effect, whereas, the effect of TPT on 5-Re 2 was not compensated. In conclusion, the present study shows that TPT acts as an unspecific, but significant inhibitor of human sex steroid hormone metabolism and suggests that the inhibitory effects are mediated by the interaction of TPT with critical cysteine residues of the enzymes.