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The coastal dune environment, due to the complex coast-to-inland gradient, contributes greatly to plant biodiversity. The ability of plants to withstand the harsh conditions of this habitat leads to a peculiar vegetation profile which may be affected by the natural and artificial degradation of the coast. Given that these disturbances are likely to increase in the future, there is a great interest in increasing the knowledge of resistance mechanisms allowing plants to colonize this stressful environment. Our focus was on physiological stress markers that could be early signals of changes before ecological disturbances become evident. Three representative species of the different dune zones, Achillea maritima, Ammophila arenaria and Helichrysum stoechas were studied during the four seasons. Winter and summer were confirmed as the most critical seasons with different levels of stress depending on the coast profile where plants grew. The shoreline-inland gradient of stress conditions was evident only for A. arenaria, whose physiology was negatively affected in foredune during summer and for this reason this species could be a useful indicator of increasingly harsh environmental conditions. Physiological performances of the studied species changed across the seasons and the occupied niches, in accordance with the respective strategies of resistance.

In two poplar species with contrasting growth performance, sugar metabolism in xylem and cambial regions can explain their different grades of tolerance to drought and their recovery rates following water deficits., Drought dramatically affects wood production by adversely impacting cambial cells and their derivatives. Photosynthesis and assimilate transport are also affected by drought conditions. Two poplar genotypes, Populus deltoides ‘Dvina’ and Populus alba ‘Marte’, demonstrated contrasting growth performance and water–carbon balance strategies; a mechanistic understanding of the water deficit response was provided by these poplar species. ‘Marte’ was found to be more anisohydric than ‘Dvina’. This characteristic was associated with the capacity to reallocate carbohydrates during water deficits. In contrast, ‘Dvina’ displayed more conservative water management; carbohydrates were preferably stored or used for cellulose production rather than to achieve an osmotic balance between the phloem and the xylem. Data confirmed that the more ‘risk-taking’ characteristic of ‘Marte’ allowed a rapid recovery following water deficit and was connected to a different carbohydrate metabolism.

Coastal dunes of the Mediterranean basin are threatened ecosystems, conservation of which is vital for both ecological and economic reasons. Understanding how dune plants and their habitat interact may deepen our knowledge of the dynamics of coastal environments. An ecophysiological and morpho-functional investigation was carried out throughout all seasons on four species typically found on the fixed dunes of central Italy. They belong to different functional groups: Cistus creticus subsp. Eriocephalus (drought semideciduous), Phillyrea angustifolia (evergreen sclerophyll), Juniperus macrocarpa (conifer) and Spartium junceum (leguminous). The aims of the study were to determine the annual patterns of plant responses, to highlight putative differences of resistance strategies between functional groups, and to identify traits which play a crucial role in plant adaptation to dune environments. Photochemical efficiency was lower in winter for all species, although it was quite steady in Juniperus. Water status never reached critical levels, probably because the summer under analysis was wetter than average. Different strategies of resistance were exhibited: leaf morphological traits and seasonal modulation of leaf pigments changed depending on the functional group. Nevertheless, all species displayed efficient adaptation to the Mediterranean environment involved in the study, showing the critical importance of how physiological and functional adjustments combine in different ways. In particular, leaf area, total carotenoid and total chlorophyll concentrations performed a prominent role in explaining how the studied plants adapt to the fixed dune environment.

The hyperactivity of aldose reductase (AR) on glucose in diabetic conditions or on glutathionyl-hydroxynonenal in oxidative stress conditions, the source of cell damage and inflammation, appear to be balanced by the detoxifying action exerted by the enzyme. This detoxification acts on cytotoxic hydrophobic aldehydes deriving from membrane peroxidative processes. This may contribute to the failure in drug development for humans to favorably intervene in diabetic complications and inflammation, despite the specificity and high efficiency of several available aldose reductase inhibitors. This paper presents additional features to a previously proposed approach, on inhibiting the enzyme through molecules able to preferentially inhibit the enzyme depending on the substrate the enzyme is working on. These differential inhibitors (ARDIs) should act on glucose reduction catalyzed by AR without little or no effect on the reduction of alkenals or alkanals. The reasons why AR may be an eligible enzyme for differential inhibition are considered. These mainly refer to the evidence that, although AR is an unspecific enzyme that recognizes different substrates such as aldoses and hydrophobic aldehydes, it nevertheless displays a certain degree of specificity among substrates of the same class. After screening on edible vegetables, indications of the presence of molecules potentially acting as ARDIs are reported.

In the present work, we investigated the response to Cd in Leptodictyum riparium, a cosmopolitan moss (Bryophyta) that can accumulate higher amounts of metals than other plants, even angiosperms, with absence or slight apparent damage. High-performance liquid chromatography followed by electrospray ionization tandem mass spectrometry of extracts from L. riparium gametophytes, exposed to 0, 36 and 360 µM Cd for 7 days, revealed the presence of γ-glutamylcysteine (γ-EC), reduced glutathione (GSH), and traces of phytochelatins. The increase in Cd concentrations progressively augmented reactive oxygen species levels, with activation of both antioxidant (catalase and superoxide dismutase) and detoxifying (glutathione-S-transferase) enzymes. After Cd treatment, cytosolic and vacuolar localization of thiol peptides was performed by means of the fluorescent dye monochlorobimane and subsequent observation with confocal laser scanning microscopy. The cytosolic fluorescence observed with the highest Cd concentrations was also consistent with the formation of γ-EC-bimane in the cytosol, possibly catalyzed by the peptidase activity of the L. riparium phytochelatin synthase. On the whole, activation of phytochelatin synthase and glutathione-S-transferase, but minimally phytochelatin synthesis, play a role to counteract Cd toxicity in L. riparium, in this manner minimizing the cellular damage caused by the metal. This study strengthens previous investigations on the L. riparium ability to efficiently hinder metal pollution, hinting at a potential use for biomonitoring and phytoremediation purposes.

In an attempt to alleviate salt-induced damage, the application of ZnO nanoparticles has been suggested. As the use of these particles has also been associated with phytotoxicity, to better clarify the effect of zinc and its possible mitigation of salt stress, we treated wheat seedlings with ZnO (nanoparticles or their bulk-scale counterparts, amended either in the growth medium, NPs and B, or sprayed on the leaves, SPNPs and SPB) with or without subsequent treatment with salt. Growth, photosynthetic parameters, zinc and ion concentration, and in situ and biochemical determination of oxidative stress in wheat leaves and/or in roots were considered. Both Zn and NaCl significantly inhibited growth and induced severe alterations in root morphology. Oxidative stress and damage decreased or increased under ZnO treatment and in saline conditions depending on the organ and on the size and mode of application of particles. In spite of the higher stress conditions often recorded in treated leaves, neither pigment concentration nor photochemical efficiency were decreased. A large variability in the effects of ZnO treatment/priming on seedling salt response was recorded, however, the presence of a cumulative negative effect of priming and salt stress sometimes observed calls for caution in the use of ZnO in protection from saline stress.

The hydrophyte Azolla filiculoides can be a useful model to assess if TiO

Background : The Zolfino bean is a variety of Phaseolus vulgaris , which is cultivated in a limited area of Tuscany, Italy, and is widely appreciated for its flavor and culinary uses. Objectives : A yellow Zolfino landrace cultivated in the Leccio-Reggello area was characterized and compared with three other varieties of Phaseolus vulgaris (i.e. the Borlotto, Cannellino, and Corona beans) in terms of its general features and potential as an antioxidant/anti-inflammatory agent. Design : The length, width, thickness, equatorial section surface, weight, volume, and seed coat section were measured in all the beans. The seed surface area was also estimated by an original empirical method. The ability of the different beans to interfere with the enzymes of the polyol pathway (that is, aldose reductase (AR) and sorbitol dehydrogenase) was tested using the supernatant after soaking the beans at room temperature and after thermal treatment, which simulated the bean-cooking process in a controlled fashion. Results : Concerning the general features, Zolfino was comparable with other beans, except Corona, in terms of surface–volume ratio, which possesses the lowest tegument thickness. Moreover, Zolfino appears the most effective in inhibiting AR activity. The inhibitory ability is unaffected by thermal treatment and appears to be associated with compound(s) present in the coat of the bean. Conclusions : The ability of Zolfino to inhibit AR, thus reducing the flux of glucose through the polyol pathway, highlights the features of Zolfino as a functional food, potentially useful in treating the dysfunctions linked to the hyperactivity of AR, such as diabetic complications or inflammatory responses. Keywords: Zolfino bean; Phaseolus vulgaris; aldose reductase; sorbitol dehydrogenase; polyol pathway (Published: 12 July 2016) Citation: Food & Nutrition Research 2016, 60: 31792 - http://dx.doi.org/10.3402/fnr.v60.31792

Willow, due to the extensive root system, high transpiration rates and ability to accumulate large amounts of cadmium, is considered particularly useful for green remediation practices. In this study two different willow species, Salix viminalis and Salix alba , were used to assess possible differences in their ability of cadmium accumulation and to analyse in detail the physiology of their response to treatments with this metal using a multidisciplinary approach. Plants were grown in hydroponics and treated with 0, 50 and 100 μM Cd 2+ (CdCl 2 ) for 7 and 14 days. Cadmium content, oxidative stress, both evaluated by biochemical and histochemical techniques, antioxidant response, leaf stomatal conductance and photosynthetic efficiency were measured in control and treated roots and/or leaves. The two willow species removed cadmium with a high efficiency from the growth solution; however, the highest contents of Cd recorded in plants grown in the presence of the lower Cd concentrations suggest a limited capacity of metal accumulation. No photochemical limitation characterised treated plants, probably due to the ability to store large amounts of Cd in the root compartment, with reduction of damage to the photosynthetic machinery. S. viminalis , able to uptake cadmium also in the root apical region, seemed to be a more efficient accumulator than S. alba and, thanks to a relatively higher antioxidant response, did not show a higher level of oxidative stress. On the basis of the above, the two plant species, in particular S. viminalis , are confirmed as useful for cadmium phytostabilisation/phytoextraction.

Yeasts from the Rhodotorula genus can accumulate large amounts of carotenoids and fatty acids in their cells. This study aimed to evaluate the potential of using cassava wastewater as a low-cost alternative substrate for the growth of Rhodotorula glutinis intended for the production of carotenoids and fatty acids. High growth of the yeast (10.28 g·L-1), as well as high productions of carotenoids (0.98 mg·L-1) and lipids (1.34 g·L-1), were obtained when Rhodotorula glutinis was cultivated in cassava wastewater as the sole source of nutrients. Moreover, the fatty acids accumulated in the yeast cells were mostly (over 50%) unsaturated, where high percentages (%) of oleic acid (59.76 ± 0.58) and linoleic acid (7.59 ± 1.18) were found when the alternative substrate was used. Results suggest that cassava wastewater presents the potential to be applied as a sole source of nutrients to support Rhodotorula glutinis growth and metabolites accumulation in its cells.

The hydrophyte Azolla filiculoides can be a useful model to assess if TiO2 NPs may in some way alleviate the Cd injuries and improve the ability of the plant to cope with this metal. With this mechanistic hypothesis, after a pre-treatment with TiO2 NPs, A. filiculoides plants were transferred to cadmium-contaminated water with or without TiO2 nanoparticles. After 5 days of treatment, cadmium uptake, morpho-anatomical, and physiological aspects were studied in plants. The continuous presence of TiO2 nanoparticles, though not increasing the uptake of cadmium in comparison with a priming treatment, induced a higher translocation of this heavy metal to the aerial portion. Despite the translocation factor was always well below 1, cadmium contents in the fronds, generally greater than 100 ppm, ranked A. filiculoides as a good cadmium accumulator. Higher cadmium contents in leaves did not induce damages to the photosynthetic machinery, probably thanks to a compartmentalization strategy aimed at confining most of this pollutant to less metabolically active peripheral cells. The permanence of NPs in growth medium ensured a better efficiency of the antioxidant apparatus (proline and glutathione peroxidase and catalase activities) and induced a decrease in H2O2 content, but did not suppress TBARS level.

In the present work, we investigated the response to Cd in Leptodictyum riparium, a cosmopolitan moss (Bryophyta) that can accumulate higher amounts of metals than other plants, even angiosperms, with absence or slight apparent damage. High-performance liquid chromatography followed by electrospray ionization tandem mass spectrometry of extracts from L. riparium gametophytes, exposed to 0, 36 and 360 &micro, M Cd for 7 days, revealed the presence of &gamma, glutamylcysteine (&gamma, EC), reduced glutathione (GSH), and traces of phytochelatins. The increase in Cd concentrations progressively augmented reactive oxygen species levels, with activation of both antioxidant (catalase and superoxide dismutase) and detoxifying (glutathione-S-transferase) enzymes. After Cd treatment, cytosolic and vacuolar localization of thiol peptides was performed by means of the fluorescent dye monochlorobimane and subsequent observation with confocal laser scanning microscopy. The cytosolic fluorescence observed with the highest Cd concentrations was also consistent with the formation of &gamma, EC-bimane in the cytosol, possibly catalyzed by the peptidase activity of the L. riparium phytochelatin synthase. On the whole, activation of phytochelatin synthase and glutathione-S-transferase, but minimally phytochelatin synthesis, play a role to counteract Cd toxicity in L. riparium, in this manner minimizing the cellular damage caused by the metal. This study strengthens previous investigations on the L. riparium ability to efficiently hinder metal pollution, hinting at a potential use for biomonitoring and phytoremediation purposes.

Seasonal changes of high density Chaetomorpha linum mats were studied in an eutrophic coastal lagoon. We measured biomass and specific growth rate and analyzed water quality, sediment labile organic matter (LOM), photosynthetic efficiency and pigments in two areas: one subjected to sediment resuspension and algal mass shuffling through specific boats and the other left undisturbed. Low disturbance enhanced algal survival under critical summer conditions, by reducing LOM and promoting growth through thalli fragmentation. Chaetomorpha linum grew fast and quickly acclimated its physiology to adverse conditions, although the mat underlayer showed low photosynthetic efficiency. Nevertheless, the ability to respond to the adverse environment was not sufficient to prevent the sudden algal decay, which occurred following a prolonged summer stress. Present results may help to plan the lagoon management through boat operations, to attain a more effective control over the algal growth and a more efficient removal of the mat.

Changes in the concentrations of bioactive gibberellins and abscisic acid in the cambial region of white poplar (Populus alba L.) were investigated in 1-year-old plants, to highlight how these phytohormone signals are modulated in response to water deficit. Plants were cultivated in pots outdoor and, at the time of maximum cambial growth (T 0), irrigation was withdrawn for 8 days, inducing a mild water deficit, thus mimicking a condition that is recurrent in Mediterranean climates when white poplar attains its maximum growth rate. The water deficit was suspended by resuming irrigation (T max) throughout a recovery period of 2 weeks (T rec). Cambial tissues were sampled at T 0, T max, and T rec. Significant changes of leaf and stem relative water content, leaf water potential, stomatal conductance, transpiration, carbon assimilation, stem shrinkage, and leaf number were induced by soil water shortage, which also negatively affected cambium development. Nevertheless, these responses were almost fully reversed following the resumption of irrigation. Water deficit induced the accumulation of large amounts of abscisic acid in cambial tissues, but the hormone was brought back to pre-stress levels after the recovery period. With regard to bioactive gibberellins, GA1 was several folds more abundant than GA4 and reached the greatest level in the plants recovering from the water status imbalance. The possible functions of gibberellins and abscisic acid in the response of cambial tissues to water deficit are discussed in view of the known physiological roles and molecular mechanisms of action of these hormonal signals.

The radial growth of plant stem is based on the development of cribro-vascular cambium tissues. It affects the transport efficiency of water, mineral nutrients and photoassimilates and, ultimately, also plant height. The rate of cambial cell divisions for the assembly of new xylem and phloem tissue primordia and the rate of differentiation of the primordia into mature tissues determine the amount of biomass produced and, in the case of woody species, the wood quality. These complex physiological processes proceed at a rate which depends on several factors, acting at various levels: growth regulators, resource availability and environmental factors. Several hormonal signals and, more recently, further regulatory molecules, have been shown to be involved in the induction and maintenance of cambium and the formation of secondary vascular tissues. The control of xylem cell patterning is of particular interest, because it determines the diameter of xylem ves- sels, which is central to the efficiency of water and nutrient transport from roots to leaves through the stem and may strongly influence the growth in height of the tree. Increasing scientific evidence have proved the role of other hormones in cambial cell activities and the study of the hormonal signals and their crosstalking in cambial cells may foster our understanding of the dynamics of xylo- genesis and of the mechanism of vessel size control along the stem. In this article, the role of the hormonal signals involved in the control of cambium and xylem develop- ment in trees and their crosstalking are reviewed.

Microalgae-based systems for the production of high value molecules are an emergent area, representing a great promise for industrial applications. The main challenge, however, is the development of high efficiency strategies for the large-scale production at low costs. The aim of this study was to evaluate the potential of ricotta cheese whey (scotta) to be used as a low-cost alternative substrate to grow the microalga Chlorella protothecoides. Furthermore, a salt and light stress condition was imposed in order to improve the carotenogenesis process. A significant reduction in lactose concentration was observed along the cultivation in the culture mediums containing scotta, indicating that the tested C. protothecoides shifted to mixotrophic growth, using the organic carbon source provided. Mixotrophic cultures presented a higher amount of biomass than the autotrophic one, however, the cellular accumulation of chlorophyll and carotenoids was higher in the latter culture. Despite this, the stress strategy that we applied enhanced carotenogenesis, allowing the cellular accumulation of well quoted carotenoids, namely astaxanthin and lutein/zeaxanthin. The results suggest that scotta has a great potential to be used as a culture medium to grow C. protothecoides. Moreover, through an adequate stress strategy it is possible to control carotenogenesis, allowing the production of high amounts of the desirable high value molecules.

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.

The role of strigolactones as plant growth regulators has been demonstrated through research on biosynthesis and signaling mutant plants and through the use of GR24, a synthetic analog of this class of molecules. Strigolactone mutants show a bushy phenotype and GR24 application inhibits the growth of axillary buds in these mutants, thus restoring the phenotype of a wild plant, which is characterized by a stronger apical dominance. In this work, we tested the effectiveness of this chemical on pea (Pisum sativum) plants following apex removal, which disrupts apical dominance and leads to axillary bud outgrowth. Moreover, we searched for relationships between the response to the strigolactone and gibberellin metabolism by applying GR24 to both climbing and dwarf peas, the latters being mutants for gibberellin biosynthesis. The results suggest that the endogenous level of the bioactive gibberellin GA1 might modulate the response of decapitated pea plants to GR24, by changing bud sensitivity to the applied strigolactone.

A filamentous fungus was isolated from Tuber borchii Vitt. fruiting bodies, and it was identified as an Arthrinium phaeospermum (Corda) M.B. Ellis strain, an “endophyte” that forms various associations with healthy leaves, stems, and roots of plants. Molecular analysis confirmed the association of this filamentous fungus with the ascocarps of all collection sites in Salento, Apulia (South Italy). An in vitro symbiosis system between Cistus creticus L. and T. borchii was set up; A. phaeospermum appears to be able to promote mycorrhiza formation in Cistus seedlings, inducing primary root shortening and an increase of secondary roots, similar to the effect of Mycorrhization Helper Bacteria (MHB). Compartmented and uncompartmented bioassays were carried out to investigate the effects of exudates/volatiles released by the truffle-hosted fungus on root architecture; the results showed root shortening in compartmented bioassay suggesting that volatiles released by the fungus alone are sufficient to alter root morphology in early phase of interaction before the mycorrhiza formation. The first evidence for an influence of a truffle-hosted fungus on ectomycorrhizal symbiosis establishment is reported.

The vegetation profile and the photosynthetic efficiency, oxidative damage, and stomatal conductance in the evergreen dwarf shrub Calluna vulgaris (L.). Hull was analyzed in a Mediterranean ecosystem characterized by intense geothermal activity. Among the higher plants present in the area, this species appears to be the sole to possess the ability to grow near the geothermal sources. The hot fluid springs strongly alter the environment in their proximity: the emitted water vapor, CO2, H2S, CH4, H3BO3, SO4 2−, and NH4 + partly condensate and precipitate to the soil, thus leading to its extreme acidification and nutrient depletion. Furthermore, the temperature starts to rise sharply just a few centimeters under the soil surface. Under this multiple stress, the individuals of C. vulgaris growing within a few meters from the springs showed lower photosystem II efficiency, higher oxidative damage to the biomembranes, and lower stomatal conductance than the individuals growing farther away. Drought and high air temperatures occurring in summer exacerbate these harsh conditions, but only the plants closer to the springs did undergo an acute, yet transient crisis, as shown by the analyzed parameters. These results suggest that the main factors of stress are related to the physical and chemical features of the soil, while the adverse climate conditions apparently are of secondary importance. The possible role of reduced stomatal conductivity in enhancing the resistance of C. vulgaris to this hostile environment is discussed.

Summary • Downwardly-growing grapevine shoots have smaller and more frequent vessels than upwardly-growing ones and, as a consequence, a lower hydraulic conductivity. Here, grapevine ( Vitis vinifera L.) shoot growth orientation was manipulated to test whether downward shoot orientation negatively affects vessel growth in the apex via a shortage of water and nutrients. • The orientation of the central vine shoot portion was inverted by two consecutive 135° bends, resulting in double-bent N-shaped vines; the central downward shoot portion was of different lengths in the experimental treatments to induce increasing reductions of shoot conductivity. These treatments reduced shoot conductivity and water flow, but had no effects on vessel development and frequency in the apex. • In a second experiment, auxin concentration was assessed in shoots of upwardly- and downwardly-growing plants. IAA concentration at the apical internodes was higher in downwardly-oriented shoots than in shoots growing upwards. In addition, a higher density and a lower vessel diameter were observed in the lower, than the upper side, of the downwardly-oriented shoot, suggesting increased accumulation of auxin in the lower side. • These results suggest that the downward orientation induces accumulation of auxin in the apex, which in turn affects the density and the size of the xylem vessels, causing reduction of hydraulic conductivity.

In order to evaluate the effect of simplified tillage systems on herbicide dissipation, diclofop-methyl residues were monitored in different soil layers (0–5 cm, 5–10 cm and 10–30 cm) under three different tillage systems: ploughing 25–30 cm deep (PT), disk harrowing 7–12 cm deep (RT) and no-tillage (NT) in a long-term experiment started in 1990 and carried out on clay soil. Diclofop-methyl residue concentrations in the soil were 0.25 ppm at peak time in topsoil and at lower quantities in the deeper layers. Diclofop-methyl residues in the topsoil were often higher with PT as compared to RT and NT. The presence of diclofop-methyl increased suddenly in untilled plots after a heavy rainfall period. This occurred in the 5–10 cm soil layer 60 days after application, and in the 10–30 cm soil layer 90 days after application. These data suggest a more rapid diclofop-methyl displacement to ground water through macropores under NT conditions.

Potato seed tubers may suffer from premature sprouting during storage, thus limiting their suitability for cultivation. Commonly used sprout suppressant treatments negatively affect but viability and therefore a reliable method to inhibit bud development must still be found for seed tubers. The monoterpene carvone ((S)-(+)-carvone) was tested in small scale experiments. The vapour of this compound fully inhibited bud growth of tubers cv. Monalisa stored at 23°C without affecting bud viability throughout 6 months of treatment. The most effective range of carvone vapour concentrations was between 0.34 and 1.06 μmol mol−1. With these qualities we can expect carvone to become a suitable sprout suppressant for seed tubers.

Summary Tubers cv. Monalisa were analysed to determine the content of abscisic acid (c-t-(+)ABA) and related metabolites in three tuber parts (eyes, sub-eye tissues and pith). Analyses were performed from the last period of tuber growth until sprouting under two different storage temperatures (3 °C and 23 °C). ABA content rises in eyes and sub-eye tissues as sprouting approaches, regardless of storage temperature. Dihydrophaseic acid is the main ABA metabolite while phaseic acid was not detected, probably because of its further metabolization to DPA. ABA-glucose ester concentrations are generally low in all tissues except in eyes before harvest. The results are discussed in relation to the current hypotheses on the role of ABA in the control of potato tuber dormancy.

The nucellus is a maternal tissue that feeds the developing embryo and the secondary endosperm. During seed development the cells of the nucellus suffer a degenerative process early after fertilization as the cellular endosperm expands and accumulates reserves. Nucellar cell degeneration has been characterized as a form of developmentally programmed cell death (PCD). In this work we show that nucellus PCD is accompanied by a considerable production of both nitric oxide and hydrogen peroxide (NO and H(2)O(2)). Interestingly, each of the two molecules is able to induce the production of the other and to cause cell death when applied to a living nucellus. We show that the induced cell death has features of a PCD, accompanied by profound changes in the morphology of the nuclei and by a massive degradation of nuclear DNA. Moreover, we report that NO and H(2)O(2) cause an induction of caspase-like proteases previously characterized in physiological nucellar PCD.

Plant growth regulators are involved in the control of potato (Solanum tuberosum) tuber dormancy. Evidence concerning the role of IAA is controversial; we therefore investigated its role by analyzing two cultivars with varying lengths of dormancy. We examined the time course of free and conjugated IAA in tuber tissue isolates from the final stages of tuber growth to the end of dormancy, the distribution of free IAA in tuber tissues by in situ analysis, and the biosynthesis of the hormone by feeding experiments. The time course of free IAA showed marked differences between the examined cultivars, although the concentration of the auxin generally was the highest at the early stages of tuber dormancy. Immunodetection showed a similar pattern of IAA distribution in both genotypes: in dormant buds from freshly harvested tubers, the free hormone accumulated mostly in apical meristem, leaf and lateral bud primordia, and differentiating vascular tissues underlying the apical meristem, while at the end of the storage period only axillary bud primordia from growing buds displayed appreciable auxin levels. Feeding experiments indicated that changes in IAA biosynthesis rate were a major cause of auxin variation in buds. In both cultivars, dormancy apparently ceased when free IAA fell below a threshold value. Despite this, our data led us to conclude that IAA would not be directly responsible for inhibiting sprouting. Instead, auxin might shorten dormancy, in a cultivar-dependent manner, by enhancing early developmental processes in buds, ultimately leading to dormancy termination.

We investigated the role of auxin on stem elongation in pea (Pisum sativum L.) grown for 10d in continuous darkness or under low-irradiance blue, red, far red and white light. The third internode of treated seedlings was peeled and the tissues (epidermis and cortex+central cylinder) were separately analyzed for the concentration of free and conjugated indole-3-acetic acid (IAA). Under red, far red and white light internode elongation was linearly related with the free IAA content of all internode tissues, suggesting that phytochrome-dependent inhibition of stem growth may be mediated by a decrease of free IAA levels in pea seedlings. The correlation between IAA and internode elongation, however, did not hold for blue light-grown seedlings. The hypothesis that the growth response under low-irradiance blue light might be correlated with the lack of phytochrome B signalling and changes in gibberellin metabolism is discussed in view of current knowledge on hormonal control of stem growth.

Two soluble proteins were isolated as major secretory products of horse sweat and of the parotid gland and characterized for structural and functional properties. The first protein, lipocalin allergen EquC1, was characterized for its glycosylation sites and bound glycosidic moieties. Only one (Asn53) of the two putative glycosylation sites within the sequence was post-translationally modified; a different glycosylation pattern was determined with respect to data previously reported. When purified from horse sweat, this protein contained oleamide and other organic molecules as natural ligands. Ligand binding experiments indicated good protein selectivity toward volatile compounds having a straight chain structure of 9-11 carbon atoms, suggesting a role of this lipocalin in chemical communication. The second protein, here reported for the first time in the horse, belongs to the group of parotid secretory proteins, part of a large superfamily of binding proteins whose function in most cases is still unclear. This protein was sequenced and characterized for its post-translational modifications. Of the three cysteine residues present, two were involved in a disulfide bridge (Cys155-Cys198). A model, built up on the basis of similar proteins, indicated a general fold characterized by the presence of a long hydrophobic barrel. Binding experiments performed with a number of different organic compounds failed to identify ligands for this protein with a well-defined physiological role.

Three Prunus species, characterised by different levels of growth vigour, were used as rootstocks for peach [Prunus persica (L.) Batsch] grafting and compared for their hormone transport rates in the sap extracted from both the grafted scions and the ungrafted rootstocks. Two of these species were hybrid rootstocks widely used in peach orchards, while the third was a commercial cultivar, which was used both as rootstock and as scion. The xylem exudates were analysed for the concentrations of indoleacetic acid and for the main cytokinins, namely zeatin, zeatin riboside, isopentenyl-adenine and isopentenyl-adenosine. In ungrafted rootstocks the growth potential was positively correlated with both indoleacetic acid and zeatin riboside transport rates. In the xylem sap of peach scions grafted on the same rootstocks, the growth potential and the zeatin riboside levels were also positively correlated, while a negative correlation was found with indoleacetic acid levels. The results are discussed in view of the most widely accepted hypothesis concerning the control exerted by rootstocks on scion growth.

The time course of free and conjugated indole-3-acetic acid (IAA) concentrations was investigated in three distinct parts (eyes, subeye tissues and pith) of potato (Solanum tuberosum L. cultivar Monalisa) tubers, from the last period of tuber growth to sprouting under two different storage temperatures (3 and 23˚C). The highest levels of both free and conjugated IAA were detected in eyes, which showed a significant increase of the free hormone concentration from harvest to the end of dormancy, regardless of storage temperature. The concentration of conjugates was higher than free IAA in eyes and subeye tissues at 23˚C, while at 3˚C conjugates prevailed only in eyes. Present results suggest the involvement of IAA in the control of potato tuber dormancy.