Shoot Cl Research Articles

Response of alfalfa (Medicago sativa L.) to diurnal and nocturnal saline sprinkler irrigations. II: shoot ion content and yield relationships

When using saline waters, sprinkling irrigation at night is a recommended practice to reduce evaporation, salt absorption by the wetted leaves and its negative effects on crops. We measured shoot ion concentrations (Cl−, Na+ and K+) and total dry matter (TDM) in alfalfa subject to diurnal and nocturnal saline sprinkler irrigations and established potential relationships among them. The work was carried out along the 2004–2006 growing seasons using EC waters from 0.5 to 5.6 dS m−1. Saline sprinkling irrigations linearly increased shoot Cl− and Na+ and decreased shoot K+. Even though daytime evaporation was much higher than nigh-time, shoot ion accumulation and TDM were similar in the diurnal and nocturnal irrigations. The salinity tolerance of alfalfa decreased in year 2006 due to increases in shoot Cl− and, particularly, shoot Na+. The lower threshold for shoot Na+ (276 meq kg−1) than for shoot Cl− (726 meq kg−1) shows that alfalfa is more sensitive to Na+ than to Cl−, and that Na+ accumulation is the preponderant cause of alfalfa yield decline after 3 years of sprinkling with saline waters.

Lotus tenuis tolerates the interactive effects of salinity and waterlogging by 'excluding' Na+ and Cl- from the xylem

Salinity and waterlogging interact to reduce growth of poorly adapted species by, amongst other processes, increasing the rate of Na(+) and Cl(-) transport to shoots. Xylem concentrations of these ions were measured in sap collected using xylem-feeding spittlebugs (Philaenus spumarius) from Lotus tenuis and Lotus corniculatus in saline (NaCl) and anoxic (stagnant) treatments. In aerated NaCl solution (200 mM), L. corniculatus had 50% higher Cl(-) concentrations in the xylem and shoot compared with L. tenuis, whereas concentrations of Na(+) and K(+) did not differ between the species. In stagnant-plus-NaCl solution, xylem Cl(-) and Na(+) concentrations of L. corniculatus increased to twice those of L. tenuis. These differences in xylem ion concentrations, which were not caused by variation in transpiration between the two species, contributed to lower net accumulation of Na(+) and Cl(-) in shoots of L. tenuis, indicating that ion transport mechanisms in roots of L. tenuis were contributing to better 'exclusion' of Cl(-) and Na(+) from shoots, compared with L. corniculatus. Root porosity was also higher in L. tenuis, due to constitutive aerenchyma, than in L. corniculatus, suggesting that enhanced root aeration contributed to the maintenance of Na(+) and Cl(-) 'exclusion' in L. tenuis exposed to stagnant-plus-NaCl treatment. Lotus tenuis also had greater dry mass than L. corniculatus after 56 d in NaCl or stagnant-plus-NaCl treatment. Thus, Cl(-) 'exclusion' is a key trait contributing to salt tolerance of L. tenuis, and 'exclusion' of both Cl(-) and Na(+) from the xylem enables L. tenuis to tolerate, better than L. corniculatus, the interactive stresses of salinity and waterlogging.

Growth and ion relations in response to combined salinity and waterlogging in the perennial forage legumes Lotus corniculatus and Lotus tenuis

Lotus tenuis (Wadst. & Kit.) is a perennial legume widely grown for pasture in the flood-prone and salt affected Pampa region of Argentina. The physiology of salt and waterlogging tolerance in L. tenuis (four cultivars) was evaluated, and compared with Lotus corniculatus (three cultivars); the most widely cultivated Lotus species. Overall, L. tenuis cultivars accumulated less Na+ and Cl−, and more K+ in shoots than L. corniculatus cultivars, when exposed to 200 mM NaCl for 28 days in aerated or in stagnant solutions. Root porosity was higher in L. tenuis cultivars due to greater aerenchyma formation. In a NaCl dose–response experiment (0–400 mM NaCl in aerated solution), L. tenuis (cv. Chaja) accumulated half as much Cl− in its shoots than L. corniculatus (cv. San Gabriel) at all external NaCl concentrations, and about 30% less shoot Na+ in treatments above 250 mM NaCl. Ion distributions in shoots were determined for plants at 200 mM NaCl. L. tenuis (cv. Chaja) again accumulated about half as much Cl− in old leaves, young leaves and stems, compared with concentrations in L. corniculatus (cv. San Gabriel). There were not, however, significant differences between the two species for Na+ concentrations in the various shoot tissues. The higher root porosity, and maintenance of lower shoot Cl− and Na+ concentrations in L. tenuis, compared with L. corniculatus, contributes to the greater tolerance to combined salt and waterlogging stress in L. tenuis. Moreover, significant variation for tolerance to combined salinity and waterlogging stress was identified within both L. tenuis and L. corniculatus.

Salinity tolerance of bermudagrass (Cynodon spp. L. C. Rich) cultivars and shoot Na, K and Cl contents under a high saline environment

SummaryIncreasing need for salt-tolerant turfgrasses continues due to population growth in arid and semi-arid regions where potable water is limited, while soil and existing water sources are salty. Bermudagrass (Cynodon spp. L. C. Rich) is widely used in these areas. Therefore, this experiment was conducted to evaluate the salt-tolerance of ten cultivars of bermudagrass under a high saline soil and water environment. Five salinity levels of irrigation water (3.30, 6.93, 10.2, 14.8 and 17.8 dS m–1) were prepared and 30 pots were surfaced-irrigated at each salinity level for 1 year. Overall top growth, root growth, K content and K:Na ratio were reduced by 75%, 45%, 77% and 94.5%, respectively; while leaf-firing, shoot Cl and shoot Na concentrations were increased by 4%, 498% and 356%, respectively, when the salinity increased from 3.3 dS m–1 to 17.8 dS m–1. Regarding the salt-tolerance of cultivars, ‘Tifway’ was superior in top growth, percentage leaf-firing, Na uptake and K:Na ratio, ‘ISF2’ in root growth, and ‘Tifdwarf’ in Cl uptake. Although ‘Tifway’ showed the greatest reduction in root dry weight, it had the lowest level of leaf-firing and lowest reduction in top growth, which could be due to having the lowest Na uptake. Cultivars exhibited marked differences in their response to salinity; however, no mortality was observed, indicating that all cultivars tolerated the salinity levels used in the experiment.

MECHANISM OF SALT TOLERANCE OF TWO OLIVE OLEA EUROPAEA L. CULTIVARS AS RELATED TO ELECTROLYTE CONCENTRATION AND TOXICITY

ISHS XXVI International Horticultural Congress: Environmental Stress and Horticulture Crops MECHANISM OF SALT TOLERANCE OF TWO OLIVE OLEA EUROPAEA L. CULTIVARS AS RELATED TO ELECTROLYTE CONCENTRATION AND TOXICITY

Characterization of rice (Oryza sativa L.) F3 populations selected for salt resistance. I. Physiological behaviour during vegetative growth

Plants belonging to a somaclonal family (R3-1-23, obtained from a salt-resistant callus of the salt-sensitive cultivar I Kong Pao (IKP, salt-sensitive)) were crossed with this intital cultivar IKP or with plants of the elite breeding line IR31785 (IR31, extremely salt-sensitive). Two other crosses were also performed: IR31 × IKP and IKP × Aiwu, where Aiwu is a moderatly salt-resistant cultivar. The physiological behaviour of F3 populations was analysed after 21 and 42 days of exposure to 0 or 30 mM NaCl and compared to the behaviour of plants selected within parental populations. A clear improvement in terms of survival percentages was demonstrated for plants issued from IR31 × 1-23 and IR31 × IKP. These F3 populations exhibited lower Na accumulation in shoots, higher Ca accumulation in roots, higher ratios of shoot P/root P than the parents after 42 days of salt exposure. Salt stress induced a decrease of shoot K, an increase of shoot Cl and proline and a decrease of osmotic potential in all populations. Correlation analysis indicated that no physiological parameter recorded in the absence of salt stress may be used as a reliable selection marker to predict the plant behaviour in salt stress conditions. K/Na ratio recorded in the stressed plants was significantly correlated with surviving percentages recorded after 90 days of salt stress, suggesting that this physiological parameter in stress conditions appears to be the most reliable selection criterion for salt resistance in rice.

141 Salinity Tolerance of Four Turfgrasses

The need for salinity-tolerant turfgrasses is increasing because of increased use of effluent water for turfgrass irrigation. Greenhouse studies were conducted to determine the relative salt tolerance and salt tolerance mechanisms of `Challenger' Kentucky bluegrass (Poa pratensis), `Arid' tall fescue (Festuca arundinacea), `Fults' alkaligrass (Puccinellia distans.), and a saltgrass (Distichlis spicata) collection. Kentucky bluegrass and tall fescue were irrigated with saline solutions at 0.2,1.7, 4.8, or 9.9 dS/m, whereas alkaligrass and saltgrass were irrigated with saline solutions at 0.2, 28.1, 32.8, or 37.5 dS/m prepared using a mixture of NaCl and CaCl2. The salinity levels that caused 50% shoot growth reduction were 9.0, 10.4, 20.0, and 28.5 dS/m for Kentucky bluegrass, tall fescue, saltgrass, and alkaligrass, respectively. Concentrations of proline, a proposed cytoplasmic compatible solute, were 25.8, 30.4, 68.1, and 17.7 μmol/g shoot fw in Kentucky bluegrass, tall Fescue, alkaligrass, and saltgrass, respectively, at the highest salinity level imposed. Bicellular, salt-secreting glands were only observed by scanning electron microscopy on leaves of saltgrass, indicating salt secretion is one of the important salt tolerance mechanisms adopted by saltgrass. Ion contents (Na, Cl, and Ca) in both shoots and roots of all grasses increased with increasing salinity levels. However, alkaligrass maintained a much lower Na, Ca, and Cl contents in roots and shoots than other grasses, suggesting that ion exclusion is one of the major salt tolerance mechanisms in alkaligrass. Tall fescue did not appear to restrict the uptake and translocation of salt in shoot tissues, but maintained a higher K/Na ratio than all other grasses under saline conditions.

Chloride Versus Sulfate Salinity Effects on Alfalfa Shoot Growth and Ionic Balance

AbstractInformation on Cl vs. SO4 salinity effects on alfalfa (Medicago sativa L) dry matter yield (DM) and cation‐anion balance is limited. Consequently, we compared Cl and SO4 salinity effects on shoot DM and ionic balance for Archer and Ladak varieties of alfalfa. A modified, flowing Hoagland solution, buffered with CaCO3, was the control: electrical conductivity (EC) = 0.7 dS m‐1. Chloride or SO4 salts of K, Ca and Mg were added to the control to get iso‐EC solutions (2–11 dS m‐1). Shoot cations (Ca, Mg, K, and Na) and their sum (C), anions (Cl, SO4, NO3 and H2PO4) and their sum (A), and DM were measured. Organic anions (C‐A) were calculated in mmolc kg‐1. The calculated hydroponic osmotic potentials (π) were from 1.4 to 1.7 times lower in Cl than in iso‐conductive SO4 solutions. As EC increased, DM decreased equally for both varieties in iso‐conductive Cl and SO4 solutions. Solution π decreased, shoot H2PO4 declined below its critical level of 65 mmolc kg‐1, shoot C stayed constant, shoot A increased; and therefore, shoot C‐A decreased. The shoot C‐A was lower in SO4 solutions. In Cl solutions shoot Cl exceeded the toxic level of 282 mmolc kg‐1. The DM was correlated positively with π, shoot H2PO4, and C‐A, and negatively with shoot Cl and SO4. We conclude that (i) iso‐conductive Cl or SO4 salinity depress DM equally, but isoosmotic SO4 is more depressive; (ii) the yield declines are probably due to any one or a combination of low water potential, toxic shoot Cl and possibly SO4, and deficiencies of shoot P and organic anions; (iii) neutral organic solutes were probably responsible for osmotic adjustment, since total ionic charges (2C) stayed constant; and (iv) P deficiency occurred despite high solution P, due to Cl or SO4 competition in saline environments.

Selecting for salt tolerance in white clover (Trifolium repens): chloride ion exclusion and its heritability

SUMMARYThe potential to improve the salt tolerance of white clover (Trifolium repens L.) was evaluated in populations developed by selecting plants within the cv. Haifa which had high and low concentrations of Cl− in the shoots. Under saline conditions (40 mM NaCl), the low‐Cl populations consistently maintained lower concentrations of both Na and Cl in all plant parts and produced more dry matter than the original parent cultivar (Haifa), or the high‐Cl populations. Under non‐saline conditions, there were no differences between populations for these characters. In young seedlings, concentrations of Cl− in the shoots of the low‐Cl and high‐Cl populations started to diverge after 4 d exposure to saline conditions and there were significant differences between populations after 6 d growth at 40 mM NaCl. Results using 36C1 suggested that the salt‐tolerant low Cl population was better able to retain 36C1 in the roots and to limit its translocation to the leaves and petioles than the high‐Cl population. Realized heritability values for shoot Cl− concentration were found to be moderate in the first cycle of selection (0.24 and 0.37 for high and low Cl− concentrations respectively), but were substantially lower (0.10 and 0.09 respectively) in the second selection cycle. We propose that it is possible to increase levels of salt tolerance in white clover by selecting for low shoot Cl− concentrations under saline conditions and that this criterion could be used at very early stages of exposure to NaCl (i.e. day 4 or 6).

Does pattern of ion accumulation vary in alfalfa at different growth stages?

Abstract AZ‐Germ Salt II, a salt tolerant line of alfalfa (Medicago sativa L.) at the germination stage, was compared with its parent line Mesa Sirsa in sand culture at the germination and seedling stages and in hydroponic culture at the adult stage under greenhouse conditions. The sodium chloride (NaCl) treatments used were 0 or 100 mol/m3 in half strength Hoagland nutrient solution. AZ‐Germ Salt II was superior to Mesa Sirsa in biomass production at all three stages. AZ‐Germ Salt II had significantly greater chloride (Cl) in the plumules and radicle than Mesa Sirsa at the germination stage. The two lines did not differ in shoot and root sodium (Na) and shoot Cl at the seedling stage. However, at the adult stage AZ‐Germ Salt II accumulated significantly higher Na in the shoots and roots and Cl in the shoots compared with Mesa Sirsa. The two lines did not differ in tissue potassium/sodium (K/Na) ratios in all three experiments, although K concentrations were higher in the seedling shoots and roots, and in...

Growth, Fruit Yield, and Ion Concentration in Tomato Genotypes after Pre- and Post-emergence Salt Treatments

The effects of increasing salinity on dry weight and ion concentration of shoots at various growth stages and on fruit yield in four tomato (Lycopersicon esculentum Mill.) genotypes were assessed. The salt treatments (35, 70, and 140 mm NaCl) were applied pre-emergence (seed sowing) (pre-E) and post-emergence (four-leaf stage) (post-E) and maintained during plant growth. Genotype salt tolerance, measured as shoot dry weight in response to increases in salt concentration, varied depending on plant growth stage and salt application time. When salt was applied pre-E, salt tolerance increased with plant age, whereas when applied post-E, 45-day-old plants were the most salt tolerant. Mature plants were similarly salt tolerant independent of the growth stage at which the salt treatments began. However, fruit yield of all genotypes was higher when salt was applied pre-E than post-E. Shoot dry weight decreased as shoot Cl and Na ion concentrations increased. During early growth stages, pre-E salt-treated plants had the highest Cl-and Na+ concentrations and the lowest shoot dry weights. However, at the advanced stages, shoot Cl- and Na Concentrations were equal for both salt application times. These results show that the plants must adapt to salinity during a period that allows them to develop a mechanism to regulate internal Cl- and Na+ concentrations and, thus, grow under high salinity.

Responses of three arid zone grass species to varying Na/Ca ratios in saline sand culture.

The effects on three grass species, Cenchrus pennisetiformis Hochst. & Steud., Leptnchloa fusca (L.) Kunth. and Panicum turgidum Forssk., of decreasing Ca2+ concentration in a saline growth medium were assessed after 7 weeks growth in sand culture. The different Na/Ca ratios of the salt treatment were 24, 49, 99, and 199, at a constant concentration of 200 mol m-3 . Leptuchloa fusca produced the highest fresh and dry biomass, and was able to maintain Na+ and Cl- Concentrations in the shoots and roots almost constant at varying external Na/Ca ratios, except that the shoot Na+ concentration increased significantly at the highest Na/Ca ratio. In C, pennisetiformis the shoot Na+ decreased, whereas the shoot Cl- concentration increased at the highest external Na/Ca ratio. But the root Na+ and Cl- concentrations in this species remained unchanged at varying Na/Ca ratios. C. pennisetiformis and L. fusca maintained almost constant K+ and Ca2+ concentrations in both shoots and roots at varying Na/Ca ratios. In P. turgidum the shoot K+ and shoot and root Ca2+ remained almost unchanged at all Na/Ca ratios, whereas the root K+ concentration decreased significantly but uniformly at the three, higher Na/Ca ratios. No consistent pattern of increase or decrease was observed in the shoot and root Na/K and Na/Ca ratios of all the species. The shoot selectivity (Sk + na ) increased consistently in C pennisetiformis with the increase in Na/Ca ratios and it decreased in L. fusca only at the highest Na/Ca ratio in the growth medium It was established that L. fusca was tolerant, C. penni-setiformis intermediate and P. turgidum relatively sensitive to low Ca2+ concentrations of the saline growth medium.

Variation in Chloride Accumulation in Hybrids and Backcrosses ofVitis berlandieriandVitis viniferaunder Glasshouse Conditions

Two glasshouse trials were conducted to examine vineyard data which suggested that the action of a single dominant gene is responsible for low chloride concentrations in petioles of vines of <i>Vitis berlandieri</i> and <i>V. berlandieri</i> x <i>V. vinifera</i> hybrids. Both trials employed a nutrient solution technique with NaCl at a concentration of 25 m<i>M</i>. To an extent, the data from the trials indicated a single gene for Cl^- exclusion derived from <i>Vitis berlandieri</i>. There was a marked segregation for high and low petiole Cl^- concentrations in one pair of backcross families, MF77-13 (<i>V. berlandieri</i> x Sultana) x Biancone or Koshu Sanjaku. However, the other pair of backcrosses investigated, MF78-01 (<i>V. berlandieri</i> x Sultana) x Biancone or Koshu Sanjaku, did not segregate in a 1:1 ratio expected from vineyard data. This result is discussed in terms of possible incorrect classification in the vineyard due to variations in rootzone salinities and/or the action of genes derived from <i>V. vinifera</i> parents which may have modified the phenotypic expression of a major gene. While there was little evidence for genotypic differences in shoot Cl^- concentrations being affected by genotypic differences in vine vigor, there were exceptions which raised the question of whether initial vine size affects the expression of a major gene for Cl^- exclusion in short-term glasshouse trials. For example, two F1 hybrids, MF77-13 (<i>V. berlandieri</i> x Sultana) and MU21-91 (<i>V. berlandieri</i> x Biancone), had high petiole Cl^- concentrations contrary to the assumption of a dominant gene for Cl^- exclusion derived from <i>V. berlandieri</i>. Both of these genotypes were less vigorous than others, and it is possible that as young vines they were less tolerant of NaCl than more vigorous vines. As a result, they accumulated greater petiole Cl^- concentrations than expected. The ratio of genotypic to phenotypic variance was greater for backcross families than for F1 hybrids (<i>V. berlandieri x V. vinifera</i>), which supported a segregation of a major dominant gene in the backcross generation.

Chloride effects on corn

Abstract Chloride (Cl) toxicity was suspected in corn (Zea mays L.) growing in a poorly‐drained Atlantic Coast Flatwoods soil where Cl toxicity of soybean {Glycine max (L.) Merr.} was a problem. Field and greenhouse research was conducted with rates of applied Cl in an effort to induce Cl toxicity in corn. ‘Trojan 114’ corn was grown in the greenhouse with Cl rates (KCl) of 0, 364, and 728 ug/g and in the field with rates of 0, 85, 170, and 340 kg/ha. Potassium sulfate (K2SO4) treatments were included to supply equivalent amounts of K as that in KCl. Phytotoxicity of corn did not occur in greenhouse or field experiments with any fertilizer treatment. In the greenhouse Cl concentrations in 26‐day old corn plants grown in a poorly‐drained Flatwoods soil (Leefield sand ‐ arenic Plinthaquic Paleudult) for the 0 and 728 ug Cl/g treatments were 5.0 and 32.7 g/kg in shoots, 1.6 and 14.9 g/kg in ear leaves, and 1.3 and 16.5 g/kg in stalks, respectively. In the field, Cl treatments applied to corn grown in a poorly‐drained Flatwoods soil (Alapaha sand ‐ arenic Plinthic Paleaquults) were not as effective in increasing Cl concentrations in shoots and ear leaves as that for corn grown in a well‐drained soil (Tifton loamy sand ‐ thermic Plinthic Paleudult) apparently because of the greater amount of residual soil Cl in the poorly‐drained soil. Concentrations of Cl in shoots of corn receiving O and 340 kg Cl/ha were 3.8 and 18.0 g Cl/kg, respectively, for corn grown in the well‐drained soil and 16.1 and 18.0 g Cl/kg, respectively, for corn grown in the poorly‐drained soil. Grain yields were not affected by fertilizer treatments on either soil and Cl concentration in grain for corn grown in the Tifton soil was not different among treatments. These data indicate that corn is not very susceptible to high levels of soil Cl.

Effects of Salts and Application Methods on English Ivy1

Abstract Na2SO4, K2SO4, NaCl, KCl or CaCl2 at concentrations of 0.25N were applied daily as a soil drench or foliar spray to established plants of English ivy (Hedera helix L.). Marginal leaf necrosis developed after 28 days on plants drenched with Cl salts although necrosis was evident after 7 days and the injury was more severe on plants sprayed with Cl salts. Shoot dry weights of plants treated with Cl salts were significantly less than those of control or spray SO4 treatments. Leaf necrosis was not evident on plants drenched with SO4 salts, but shoot dry weights were significantly less than those of plants sprayed with SO4 salts or water. Shoot Na was greater from spray-applied Na salts compared to soil-treatments while shoot Cl was greater in soil-treated plants compared to spray Cl treatments. Shoot Cl generally corresponded with the severity of plant injury whereas shoot Na did not.

Tolerance of Honeylocust Seedlings to Soil-applied Salts1

Abstract Salt tolerance of honeylocust (Gleditsia triacanthos inermis Willd.) was determined using 2 month-old potted seedlings salinized with 200 ml of NaCl, KCl and Na2SO4 at concentrations of 0.05N, 0.15N and 0.25N applied daily to soil. Leaflets of plants receiving Cl developed a tip and marginal necrosis while leaflets of plants receiving Na2SO4 were uninjured. Shoot dry weight of plants receiving NaCl and KCl (0.15N and 0.25N) were significantly lower than plants from control and all concentrations of Na2SO4 treatment Total soluble salts were not responsible for injury. Na had no adverse effect on growth although shoot Na levels were greater than 2% of dry weight in NaCl (0.15N and 0.25N) plants. Shoot Cl was a reliable index of the degree of salt injury, for the greater the tissue Cl, the more rapid the onset and the more severe the injury. Root Na and Cl levels were inconsistent and did not reflect the degree of injury observed. Honeylocust, although reportedly highly salt tolerant, was severely injured by exposure to Cl salts and this injury, correlated with shoot tissue analyses, suggested a specific ion effect.