The effect of salinity on the antioxidative system of root mitochondria and peroxisomes of a cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species L. pennellii (Lpa) was studied. Salt stress induced oxidative stress in Lem mitochondria, as indicated by the increased levels of lipid peroxidation and H(2)O(2). These changes were associated with decreased activities of superoxide dismutase (SOD) and guaiacol peroxidases (POD) and contents of ascorbate (ASC) and glutathione (GSH). By contrast, in mitochondria of salt-treated Lpa plants both H(2)O(2) and lipid peroxidation levels decreased while the levels of ASC and GSH and activities of SOD, several isoforms of ascorbate peroxidase (APX), and POD increased. Similarly to mitochondria, peroxisomes isolated from roots of salt-treated Lpa plants exhibited also decreased levels of lipid peroxidation and H(2)O(2) and increased SOD, ascorbate peroxidase (APX), and catalase (CAT) activities. In spite of the fact that salt stress decreased activities of antioxidant enzymes in Lem peroxisome, oxidative stress was not evident in these organelles.

Salinity up‐regulates the antioxidative system in root mitochondria and peroxisomes of the wild salt‐tolerant tomato species Lycopersicon pennellii

Soils that contain toxic amounts of minerals or are deficient in essential plant nutrients are widespread globally and seriously constrain rice production. New methods are necessary to incorporate the complex adaptive traits associated with tolerance of these abiotic stresses, while simultaneously retaining the high yield potential of rice varieties when conditions are favorable. Significant progress in the genetic characterization of stress response pathways and recent advances in genomics have provided powerful tools for in-depth dissection of tolerance mechanisms. Additionally, tolerance of most of these abiotic stresses in rice is controlled by a few QTLs with large effects despite the intricacy of the numerous traits involved. Genetic dissection of these QTLs and their incorporation into high-yielding varieties will significantly enhance and stabilize rice productivity in these problem soils. Current efforts at IRRI and in rice breeding programs worldwide are seeking to explore diverse germplasm collections and genetically dissect the causal mechanisms of tolerance to facilitate their use in breeding. This review focuses on salinity and P and Zn deficiency as the major problems encountered in rice soils, and examines current understanding of the mechanisms involved and efforts toward germplasm improvement.

Genetic and genomic approaches to develop rice germplasm for problem soils

Differential expression and regulation of antioxidative enzymes by cadmium in pea plants

A proteomic approach to analyzing drought- and salt-responsiveness in rice

Salinity tolerance of purslane (Portulaca oleracea L.) is achieved by enhanced antioxidative system, lower level of lipid peroxidation and proline accumulation

Application of a 100-mM NaCl salt stress to wheat seedlings of a salt-tolerant (Triticum durum var Ben Bechir) and a salt-sensitive (Triticum aestivum var Tanit) species decreases the fresh and dry weights of roots especially in the salt-sensitive species, and slightly increases the ratio of dry to fresh weight, especially in the salt-resistant species All peroxidase activities are increased by salt stress, the water-soluble peroxidase activity being increased much more in the salt-sensitive than in the salt-tolerant species, while the opposite result is observed with the cell-wall peroxidase activity Some water-soluble peroxidases have been hypothesised to have auxin oxidase activity (which might explain the effect observed on the root biomass), while the cell-wall peroxidases would be involved in lignification Histochemical observation confirms a more intense lignification in the root cells of the salt-tolerant species compared to the sensitive species, under the effect of NaCl

Root growth and lignification of two wheat species differing in their sensitivity to NaCl, in response to salt stress.

— White light irradiation of a microsomal fraction from etiolated plants affects their ATP-dependent Ca2+ accumulation by inhibiting active uptake and enhancing passive efflux. The succinate-dependent mitochondrial Ca2+ accumulation as well is decreased by light. The wavelength dependence of these light effects as well as their low quantum yield suggest non-phototransformable protochloro-phyll(ide) [PChl(ide)] to be the photoreceptor. PChlide has been isolated from corn leaves pretreated with 5-amino levulinic acid. Addition of Pchlide causes photosensitization of an otherwise light insensitive microsomal Ca2+ accumulation. The observed light effect may be due to contamination of the mitochondrial as well as the microsomal fractions with PChl(ide)‡ containing particles. Irradiation of the intact tissue leads to the almost complete disappearance of the light effect on the in vitro Ca2+ accumulation.

PROTOCHLOROPHYLL(IDE)630 PHOTOSENSITIZES ACTIVE Ca2+ ACCUMULATION IN MICROSOMAL AND MITOCHONDRIAL FRACTIONS ISOLATED FROM PLANTS

Iron-superoxide dismutase and monodehydroascorbate reductase transcripts accumulate in response to internode rubbing in tomato

Salt stress increased PAL activity, did not appreciably alter the Ca content, decreased the K content and increased the Na content of wheat roots. Apart from Na, the effects were slightly more pronounced in a salt-sensitive than in a salt-tolerant species.

Pal activity and ionic contents of two wheat species differing in their sensitivity to NaCl, in response to salt stress (case report)

Salt stress alters the meristem size, the mitotic index, the progress of cell division and the size of the cortical cells in wheat roots. The effects are usually more, but not much more pronounced with the sensitive species Triticum aestivum (var. Tanit) than they are with the more tolerant species Triticum durum (var. Ben Bechir). It may be that the main mechanisms responsible for the relative sensitivity/tolerance of wheat to salt stress are not localized in the root system.

Abdelkader Ayadi

Papers

Root growth and lignification of two wheat species differing in their sensitivity to NaCl, in response to salt stress.

PROTOCHLOROPHYLL(IDE)630 PHOTOSENSITIZES ACTIVE Ca2+ ACCUMULATION IN MICROSOMAL AND MITOCHONDRIAL FRACTIONS ISOLATED FROM PLANTS

Iron-superoxide dismutase and monodehydroascorbate reductase transcripts accumulate in response to internode rubbing in tomato

Pal activity and ionic contents of two wheat species differing in their sensitivity to NaCl, in response to salt stress (case report)

Root Cell Characteristics of Two Wheat Species Differing in Their Sensitivity to NaCl in Response to Salt Stress