Carmelina Spanò

Responses to desiccation injury in developing wheat embryos from naturally- and artificially-dried grains.

Grains of wheat (Triticum durum Desf. cv. Cappelli) were collected at different stages of maturation. To test whether the response to desiccation injury is correlated with physiological stage and/or water content, one lot of grains at each stage was artificially dried until its water content was comparable to that of the subsequent stage. Several stress parameters were analysed in embryos isolated from naturally-and artificially-dried grains. In particular, the content of dehydrins, hydrogen peroxide and the activity of ribonucleases and of antioxidant enzyme were studied. Neutral ribonucleases, unlike acidic ones, seemed to be correlated with grain water content. In parallel with these analyses the presence of dehydrins was also examined. Dehydrin accumulation was found to vary with drying rate, and more isoforms of dehydrin were present in artificially dried than in naturally-dried grains. Artificial drying resulted in accumulation of hydrogen peroxide, while the content of this molecule was much lower in embryos from naturally fully-ripened grains. While the activities of ascorbate peroxidase (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), glutathione reductase (GR, EC 1.6.4.2), and glutathione peroxidase (GPX, EC 1.11.1.9), were generally higher early in maturation, the activity of catalase (CAT, EC 1.11.1.6) increased in mid-maturation and decreased in fully-ripe embryos. Different protective mechanisms seem to act in combination but their relative importance changes as maturation progresses and in response to the drying method.

Calystegia soldanella : dune versus laboratory plants to highlight key adaptive physiological traits

Coastal plants live in heterogeneous and potentially stressful environments in which multiple stress factors may coexist. Some of these constraints can induce oxidative stress with consequent damage to cell components and structures. To contrast oxidative damage plants have evolved antioxidant systems, including both enzymatic and non-enzymatic molecules. The aim of this study was to highlight main physiological traits evolved by plants to survive in coastal environment through a comparison of nutritional and physiological parameters between dune (DC) and laboratory-grown (LC) plants of Calystegia soldanella (L.), a typical dune plant. In comparison with laboratory plants, dune plants living on a soil with relatively low nutrient content, were characterised by lower total nitrogen, K+ and phosphate content and by lower K+/Na+, PO42−/Cl− and N/Cl− ratios. Pigment content was significantly higher in LC than in DC plants. Despite their higher hydrogen peroxide content and lipid peroxidation, dune plants had a membrane damage, assessed by the electrolytic conductivity method, not significantly different from that of LC plants. Phenol and ascorbate pools, glutathione reductase and catalase activities were significantly higher in dune than in laboratory plants. Although the stress level was high, coastal plants were well protected against oxidative damage and proline, phenols, ascorbate, glutathione reductase and catalase seemed to play a pivotal role in plant adaptation to the constraints of coastal environment.

Plant adaptation to extreme environments: the example of Cistus salviifolius of an active geothermal alteration field.

Cistus salviifolius is able to colonise one of the most extreme active geothermal alteration fields in terms of both soil acidity and hot temperatures. The analyses of morpho-functional and physiological characters, investigated in leaves of plants growing around fumaroles (G leaves) and in leaves developed by the same plants after transfer into growth chamber under controlled conditions (C leaves) evidenced the main adaptive traits developed by this pioneer plant in a stressful environment. These traits involved leaf shape and thickness, mesophyll compactness, stomatal and trichome densities, chloroplast size. Changes of functional and physiological traits concerned dry matter content, peroxide and lipid peroxidation, leaf area, relative water and pigment contents. A higher reducing power and antioxidant enzymatic activity were typical of G leaves. Though the high levels of stress parameters, G leaves showed stress-induced specific morphogenic and physiological responses putatively involved in their surviving in active geothermal habitats.

Ageing in embryos from wheat grains stored at different temperatures: oxidative stress and antioxidant response

In the present work we studied oxidative stress as an important cause of seed deterioration during ageing in embryos from durum wheat grains stored at room temperature and at low temperature (10°C). The protective role of low temperature on seed viability was confirmed. The increase of hydrogen peroxide content during dry storage was strongly correlated with the decrease of germinability. Ascorbate and glutathione showed a good correlation with grain germinability and significantly increased upon imbibition, in particular in embryos from viable grains. Ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX) and catalase (CAT) were studied quantitatively (enzymatic assays). APX, GR, and GPX were also studied qualitatively by native PAGE. The enzymes were active in dry, still viable, embryos whereas no activity was detected in non-viable embryos. With the exception of APX, all enzymatic activities decreased upon imbibition. The study of grains stored in different conditions indicated a negative correlation between the efficiency of the antioxidant enzymatic machinery and the age of the grain. The differences detected in differently stored materials confirmed that both germination parameters and the length of storage period are important in determining grain condition.

Dormancy and germination in wheat embryos: ribonucleases and hormonal control

Acidic and neutral ribonucleases (RNases) were studied in embryos of Triticum durum cv. Cappelli and the effects of abscisic acid (ABA) and gibberellic acid (GA3) were analysed. RNases activities increased during germination and were comparable in dormant and non-dormant embryos imbibed for 24 h. ABA generally inhibited ribonucleolytic activities, while GA3 only affected dormant embryos. To assess whether changes in RNase activities during germination or following hormonal treatment required new transcriptional or translational action, cycloheximide or cordycepin were used. The action of inhibitors of acidic RNase activity was found only in non-dormant-embryos. Findings obtained in the present work concur with a change of the ribonucleolytic pattern in the shift from dormant to non dormant metabolism.

Ribonucleases during ripening and after-ripening in Triticum durum embryos

Summary Total and polyadenylated RNA content changes during ripening and after-ripening in embryos of Triticum durum cv. Cappelli. In this work, RNase activity was studied by means of enzymatic assays and activity staining SDS-PAGE in embryos at different stages of maturation and after-ripening. Qualitative and quantitative changes of RNases were found. Of particular interest was the continuous presence of acidic RNase in embryos, and the disappearance of neutral RNase activities during after ripening. Salt-inhibited RNases disappeared 42 days after anthesis, while salt-stimulated RNases with higher mobility disappeared in fully ripened embryos. Salt-stimulated RNases with lower mobility disappeared during after-ripening. The disappearance of neutral RNase activities during ripening may be related to the different physiological status induced by dehydration.

Phytochemicals and antioxidant capacity in four Italian traditional maize (Zea mays L.) varieties

Abstract Flours of four pigmented (from orange to red and dark red) local Italian corns, studied for their soluble, soluble conjugate, and insoluble-bound phenols and flavonoids, showed a prevalence of the insoluble-bound fraction (70–80%). Correlations were found between the flours antioxidant capacity, measured with CUPRAC, FRAP, and DPPH methods, and soluble phenols and flavonoids content. A correlation was also found between ascorbic acid content and flours antioxidant power. Anthocyanins were present in small amounts in the red/dark red seeds; however, acid-alcohol assays and spectral analyses of pericarp extracts indicated the presence of red-brick phlobaphenes in these varieties. Spectrophotometrically quantified total carotenoids were significantly higher in one of the local varieties (Nano); RP-HPLC analyses indicated that the local varieties contained significantly higher amounts of zeaxanthin and β-carotene, and lower amounts of lutein, than a commercial line. Among local varieties, Nano expressed the highest levels of zeaxanthin, β-carotene, and β-cryptoxanthin.

Morpho-physiological plasticity contributes to tolerance of Calluna vulgaris in an active geothermal field

Geothermal alteration fields are very prohibitive environments, limiting vegetation establishment and growth. Inthepresentstudy,theecologicalspecialisationofthepioneerplantCallunavulgaris(L.)Hullwasinvestigated,assuming that its ability to survive in geothermal habitats derives from a fine regulation of morpho-physiological traits. Mature leaves of C. vulgaris were sampled from plants close to a fumarole (near), and from plants living at a distance of some metres (intermediate) or ~1km (distant) from a fumarole. Along the sampling sites, a gradient of soil-pH and temperature values occurred, with near plants facing the highest soil temperature and the lowest soil pH. A regulation of constitutive morpho- anatomical and physiological traits in response to different stress levels occurred. A progressive reduction of leaf exposed surfaceandhairdensityandmucilages,combinedwithagradualincreaseofoxidativestresslevels,ofphenolsandascorbate, was observed from distant to near plants. Near plants showed an increase in stomatal density and in lignin and cuticle thickness, and the highest activity of ascorbate peroxidase. Except for high glutathione concentrations, in distant plants antioxidantmachinerywasconsistentlylessactive.Theapparentmorphologicalandphysiologicalplasticitydemonstratedin the present research contributed to the capability of these plants to tolerate the prohibitive, highly changing environmental conditions of the geothermal field.

Indole-3-acetic acid metabolism and growth in young kiwifruit berry

The patterns of auxin concentration and metabolism were investigated in distinct kiwifruit portions and compared with the rate of fruit growth during early developmental stages. Indole-3-acetic acid (IAA) level was higher in inner fruit tissues, particularly in younger fruit, while the hormone was barely detectable in outer tissues. Modulation of free IAA concentration did not appear to depend tightly on conjugation of the hormone. Despite the lack of a strong correlation between the levels of IAA and enzymes involved in its catabolism, in some portions of the fruit a low hormone level corresponded to a higher IAA degradation activity. An inverse correlation was also observed between hormone levels and the appearance/increase in some bands with high mobility in peroxidase gel activity assay. Phenols, compounds with a potential auxin-protecting activity, appeared to be involved mostly in photoprotection of the fruit than in the regulation of IAA levels. Beyond catabolism and conjugation, other metabolic pathways, particularly those occurring in the developing seeds, may have decisively influenced auxin levels in fruit tissues, as well as the amount of the hormone exported from the fruit. The latter, estimated by analyzing the concentration of IAA in the sap exuded from the pedicel, showed a time course which was similar to that displayed by inner fruit tissues. Furthermore, similarities were found between the pattern of IAA concentration in inner fruit tissues and fruit growth rate. The possible role of IAA in promoting growth during early fruit development is discussed.

Morpho-anatomical and physiological traits of Agrostis castellana living in an active geothermal alteration field

Abstract Agrostis castellana is one of the few plants colonizing one of the most extreme geothermal alteration fields characterized by low pH and high temperature of soil. The study of species surviving in these multi-stress habitats can help to know more in deep the adaptive ability of plants. In this work morpho-anatomical, functional and physiological traits of leaves of A. castellana living few meters from fumaroles were studied, focusing on their putative ecological significance. Some typical xeromorphic traits occurred in the leaves of these plants: abundant cutinization, cell wall thickening, slightly convolute and adaxially ribbed leaf blades, tissutal reinforcements by sclereids, pubescence, protected stomata and densely packed mesophyll. Abundant pectins, important in both water balance adjusting and as monosaccharide source, were observed in epidermal cell walls. Despite the low value of relative water content, indicative of a disturbed hydric state, oxidative damage, in terms of lipid peroxidation, indicative of membrane damage, was significantly lower than in other plants of the same environment, probably tanks to an adequate antioxidant response based mainly on enzymatic machinery. Interestingly catalase activity was not inhibited by extreme conditions of the geothermal alteration field as in other plants of the same habitat. In conclusion, a cooperation of xeromorphic traits and antioxidant response seems to make A. castellana able to survive in such a prohibitive environment.