Antonio Cerdá

Salinity induced potassium deficiency in maize plants

Summary Maize (Zea mays L.) plants were grown in ½ Hoagland nutrient solutions to study the effect of two K+ levels (0.1 and 1 mmol/L) combined with low (0.1mmol/L) and high NaCl salinity (100mmol/L) on K+ uptake and translocation. Net uptake rates of K+ were determined by disappearance in the medium and by plant content. Salinity significantly decreased shoot growth when the level of K+ in the solution was 0.1 mmol/L, probably due to a salinity-induced K+ deficiency. NaCl reduced K+ net uptake rates and to a greater extent K+ translocation from root to shoot, which resulted in a lower K+ shoot content and a higher K+ root content. The inhibitory effect of salinity on K+ translocation was stronger with low K+ concentration in the nutrient solution. Net uptake of K+ was dependent on K+ concentration in the root medium and on K+ status of the root.

Implications of calcium nutrition on the response of Phaseolus vulgaris L. to salinity

The effect of Ca2+ level in the growth medium on the response of germination and early seedling growth of Phaseolus vulgaris to NaCl salinity was investigated. When NaCl concentration was increased germination and early seedling growth was decreased. The addition of Ca2+ to the media increased both germination percentage and seedling growth. Chloride concentrations were not affected by the level of Ca2+. Potassium and Ca2+ concentrations and transport from roots to shoots were decreased by NaCl, but were restored by increasing Ca2+ in the medium. The opposite was true for Na+. Leakage of NO3- and H2PO4- was increased by salinity and reduced by high Ca2+ in the medium. The results are discussed in terms of the beneficial effects of calcium for plant growth under saline conditions.

Fruit quality of grafted tomato plants grown under saline conditions

Summary Tomato seedlings (cvs. ‘Fanny’ and ‘Goldmar’) were grafted onto the tomato rootstock hybrid AR-9704, using the cleft grafting method, and grown under greenhouse conditions. Tomato fruit yield and quality from plants exposed to 0, 30 or 60 mM NaCl, comparing grafted with ungrafted plants, was studied. Fruit yield was determined, and the chemical quality of fruit was analysed by measurements of sugars, lycopene, -carotene, ascorbic acid and mineral composition, and by determination of titratable acidity and soluble solids. Fruit yield was higher in grafted than in ungrafted plants for both varieties, for 0, 30 and 60 mM NaCl. Salinity increased soluble solids, glucose and fructose, mainly at 60 mM NaCl, while ascorbic acid increased significantly only for grafted plants at 0 mM NaCl. The concentrations of -carotene and lycopene were not affected by salinity, but a large increase due to grafting was observed for all treatments. Sodium, chloride and nitrate ion concentrations were higher in ungrafted than in grafted plants, for the 60 mM NaCl treatment. Thus, grafting could be a useful tool to increase tomato fruit quality.

SALINITY AND AMMONIUM/NITRATE INTERACTIONS ON TOMATO PLANT DEVELOPMENT, NUTRITION, AND METABOLITES

The interactions between NaCl and different NO3 −NH4 + ratios were investigated. Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse, in 120L capacity containers filled with continuously aerated Hoagland nutrient solution. Treatments were added to observe the combined effect of two NaCl levels (30 and 60 mM) and three millimolar ratios of nitrate: ammonium (14:0, 12:2, 10:4) on growth, nutrition, and contents of chlorophyll and sugars. Saline treatments decreased growth, which was partly restored by NH4 + treatment. The leaf mineral composition showed a marked effect of nitrogen (N) source, while salinity only affected NO3 − concentration. Changing the NO3 −:NH4 + ratio from 14:0 to 12:2 and 10:4 produced progressive increases in the concentrations of iron (Fe), chlorophyll, and reducing sugars in leaves. Therefore, the deleterious effect of salinity on biomass production can be minimized by the use of nutrient solutions containing higher NH4 + concentrations, since this seemed to be correlated with increases in nitrogen assimilation and the levels of Fe and chlorophyll.

Water and nutrient uptake of grafted tomato plants grown under saline conditions

Summary Tomato seedlings, cvs. Fanny and Goldmar, were grafted on the rootstock cv. AR-9704 using the ‘tongue approach grafting’ method and were grown in a crop chamber. The response of the grafted varieties to salt exposure (75 mmol L −1 NaCl) was compared with ungrafted plants. Under non saline conditions, root hydraulic conductance (L 0 ) of both cultivars decreased when they were grafted. When salinity was increased, no significant alteration of L 0 between grafted and ungrafted plants was observed. The L 0 measurements made below and above the graft union, indicated that the graft union was not a barrier to water passage. Salinity treatment significantly increased the percentage of water movement via the apoplastic pathway for grafted and ungrafted plants. Chloride and sodium concentrations in the xylem and leaves of NaCl treated plants were higher in ungrafted than in grafted plants. The small effect of NaCl treatment on grafted plants could indicate that grafting provides a useful tool for increasing the salt stress resistance of plants.

Effect of salinity on the growth and nitrogen uptake by wheat seedlings

Abstract Saline conditions affect nitrogen (N) assimilation of higher plants. To study the effect of salinity and N source on growth and N uptake in wheat (Triticum aestivum L.), plants were grown in a growth chamber under controlled conditions. The nutrient solution contained 4 mM N, applied as either calcium nitrate [Ca(NO3)2] or ammonium sulfate [(NH4)2SO4], or a mixture of both, and the salinity treatments consisted in two levels of sodium chloride (NaCl) (1 and 60 mM). Salinity significantly reduced shoot and root growth and the effect of the N source was dependent on which salinity treatment was applied. Salinity decreased the net uptake rate of nitrate (NO3) and NO3+ammonium (NH4), but had little effect on NH4 uptake when this nutrient was applied alone. Dark conditions affected NO3 uptake to a greater extent than NH4 uptake. The best N source for wheat growth was a mixture of NO3 and NH4, especially under saline conditions or periods of low irradiance.

Time course of solute accumulation and water relations in muskmelon plants exposed to salt during different growth stages

Abstract A greenhouse experiment was carried out to determine the effect of salinity on the water relations, osmotic adjustment and growth of melon plants (Cucumis melo, L.). Three saline treatments (20, 40 and 60 mM NaCl corresponding to 4, 6 and 8 dS m−1, respectively) were applied at four different phenological stages (seedling, flowering, fruit set and fruit growth) to compare the effect of the time of application on the parameters studied. A reduction in stomatal conductance, water potential and osmotic potential was observed with all treatments. The degree of osmotic adjustment observed indicated that no changes in leaf turgor occurred after any of the saline treatments applied at the different stages. Total sugar concentration increased in the leaves immediately after all treatment applications but later reverted to control values. No changes were observed in the total amino acid concentration. Similar and significant increases were observed in leaf Cl− and Na+ concentrations, which were greater at higher NaCl concentrations. Analysis of the contribution by the different solutes showed that inorganic compounds were increased to a greater extent than organic compounds after treatment application. Measurements of shoot height and leaf elongation rate showed that only salt applications during fruit set produce slight reductions in these two parameters while greater alterations were observed with the rest of the treatments.

Ionic and osmotic effects on nitrate reductase activity in tomato seedlings

Summary To discriminate between ionic and osmotic effects on nitrate reductase activity, isotonic solutions of Cl − , SO 4 2− and PEG were used in intact tomato seedlings. PEG was found to be more detrimental to seedling growth than isotonic Cl − or SO 4 2− - treatments. Net NO 3 2− uptake was inhibited more by Cl 2− salts than by SO 4 2− salts, and drastically decreased with PEG. In vivo NRA in leaves was unaffected by the SO 4 2− and PEG treatments, whereas it was reduced by C1 − . The leaf osmotic potential was similar under the 3 types of stresses (CI-, sol- and PEG), which indicates that an osmotic effect on NRA can be disregarded. Under our experimental conditions, the primary cause of a decrease of NRA in the leaves was a specific effect associated with the presence of Cl − salts in the external medium. This effect of Cl − seems to be due to a reduction in NO 3 2− uptake and consequently a lower NO 3 2− concentration in the leaves, although a direct effect of Cl − on the activity of the enzyme cannot be discarded.

Phosphorus uptake and translocation in salt-stressed melon plants

Summary Melon seedlings ( Cucumis melo L. cv.Galia) were grown hydroponically to study the effect of salinity (80 mmol/LNaCl) on phosphate (Pi) uptake and translocation at two levels of Pi (25 μmol/L and 1 mmol/L). Net uptake rates of Pi were determined by depletionof the medium and by plant content. Salinity decreased Pi uptake at low Pi (high affinity uptake mechanism), 25 μmol/L, although no specific competitive inhibition of Pi uptake by Cl − was observed. When plants were grown with high Pi (1 mmol/L), the uptake of Pi through the low affinity system was increased by 80 mmol/L NaCl. Salinity also reduced the phosphorus flux, as Pi, through the xylem. It is hypothesised that high levels of NaCl decrease the mobility of Pi stored in vacuoles, and as a result, inhibit export from this storage compartment to other parts of the plant.

Salt tolerance of two lemon scions measured by leaf chloride and sodium accumulation

Abstract Effects of salinity on growth, ion content, water relationships, and chlorophyll and proline levels were measured on one‐year‐old ‘Verna’ and ‘Fino’ lemon (Citrus limon [L] Burm. F.) scions budded to either Sour orange (C. aurantium L.) or macrophylla (C. macrophylla Wester) rootstock. Trees were grown in nutrient solutions containing 2 (control), 40, or 80 mol m‐3 NaCl for 75 days. Growth of all combinations was reduced by salinity, but this effect was greater for both scions budded on macrophylla. Leaf chloride and sodium concentrations were lower in both scions budded on Sour orange. Leaf salt concentration was scion dependent. Leaves of ‘Fino’ lemon had higher levels of both chloride and sodium than did leaves of ‘Verna’ lemon, regardless of the rootstock considered. Despite an accumulation of chloride and sodium in the leaves of salinized trees, leaf water potential and leaf water content increased above the control level. However, stomatal conductance declined in all rootstock/scion combina...