Responses to changes in Ca2+ supply in two Mediterranean evergreens, Phillyrea latifolia and Pistacia lentiscus, during salinity stress and subsequent relief.
OBJECTIVE
Changes in root-zone Ca(2+) concentration affect a plant's performance under high salinity, an issue poorly investigated for Mediterranean xerophytes, which may suffer from transient root-zone salinity stress in calcareous soils. It was hypothesized that high-Ca(2+) supply may affect differentially the response to salinity stress of species differing in their strategy of Na(+) allocation at organ level. Phillyrea latifolia and Pistacia lentiscus, which have been reported to greatly differ for Na(+) uptake and transport rates to the leaves, were studied. Methods In plants exposed to 0 mM or 200 mM NaCl and supplied with 2.0 mM or 8.0 mM Ca(2+), under 100 % solar irradiance, measurements were conducted of (a) gas exchange, PSII photochemistry and plant growth; (b) water and ionic relations; (c) the activity of superoxide dismutase and the lipid peroxidation; and (d) the concentration of individual polyphenols. Gas exchange and plant growth were also estimated during a period of relief from salinity stress. Key Results The performance of Pistacia lentiscus decreased to a significantly smaller degree than that of Phillyrea latifolia because of high salinity. Ameliorative effects of high-Ca(2+) supply were more evident in Phillyrea latifolia than in Pistacia lentiscus. High-Ca(2+) reduced steeply the Na(+) transport to the leaves in salt-treated Phillyrea latifolia, and allowed a faster recovery of gas exchange and growth rates as compared with low-Ca(2+) plants, during the period of relief from salinity. Salt-induced biochemical adjustments, mostly devoted to counter salt-induced oxidative damage, were greater in Phillyrea latifolia than in Pistacia lentiscus.


CONCLUSIONS
An increased Ca(2+) : Na(+) ratio may be of greater benefit for Phillyrea latifolia than for Pistacia lentiscus, as in the former, adaptive mechanisms to high root-zone salinity are primarily devoted to restrict the accumulation of potentially toxic ions in sensitive shoot organs.
Tattini
Massimiliano
M
Istituto per la Valorizzazione del Legno e delle Specie Arboree, IVALSA, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019, Sesto F.no, Firenze, Italy. m.tattini@ivalsa.cnr.it
Traversi
Maria Laura
ML
D000704:Analysis of Variance; D002118:Calcium / Q000494:pharmacology*; D002241:Carbohydrates / Q000737:chemistry; D002245:Carbon Dioxide / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry; D015227:Lipid Peroxidation; D029592:Oleaceae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D009995:Osmosis; D010636:Phenols / Q000737:chemistry; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000187:drug effects / Q000378:metabolism; D027927:Pistacia / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018526:Plant Transpiration; D059808:Polyphenols; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology*; D012987:Soil; D013482:Superoxide Dismutase / Q000378:metabolism
D002241:Carbohydrates; D005419:Flavonoids; D010636:Phenols; D045332:Photosystem II Protein Complex; D059808:Polyphenols; D012987:Soil; D002245:Carbon Dioxide; D012965:Sodium Chloride; D013482:Superoxide Dismutase; D002118:Calcium