Rossano Massai

Hormonal relationships in xylem sap of grafted and ungrafted Prunus rootstocks

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.

Effects of foliar and fruit addition of sodium selenate on selenium accumulation and fruit quality

BACKGROUND We investigated the effects of the foliar and fruit application of sodium selenate on selenium (Se) accumulation, fruit growth and ripening in peach and pear. Trials were conducted in two growing seasons. In 2008 selenate was applied at a rate of 0.1 and 1.0 mg Se L⁻¹ to the leaves of peach. In 2009 selenate was applied at a rate of 1 mg Se L⁻¹ via foliar (LT) or fruit (FT) application to peach and pear. RESULTS The foliar addition of selenate to peach resulted in an increase in Se concentration both in leaves and fruit. The higher Se content in fruit resulted in an increase in flesh firmness and a decrease in soluble solid content. LT significantly increased the Se content in the leaves and fruit of peach and pear, and leaves showed the highest Se concentrations. FT increased the fruit Se concentration in both crops, and it was more effective than LT in increasing Se content. After storage, flesh firmness decreased in all treatments, but it was significantly higher in FT compared to LT and control samples. CONCLUSION Foliar and fruit selenium spraying appeared effective in increasing the Se content of fruit in peach and pear. The enhanced Se concentration affected the shelf life of fruit, delaying the reduction in flesh firmness and fruit ripening, thus positively affecting fruit storage.

Non-destructive evaluation of ripening and quality traits in apples using a multiparametric fluorescence sensor.

BACKGROUND The detection of pigments and colourless flavonoids in apples can provide a useful indication of fruit quality. Optical methods are preferable because they are fast and non-destructive. In this study, a fluorescence-based portable sensor was used in order to non-invasively determine the content of chlorophylls, anthocyanins and flavonols in Fuji, Granny Smith and Golden Delicious apple cultivars. The aim was to define new non-destructive optical indices of apple quality. RESULTS The anthocyanin index (ANTH) in Fuji was higher in the sunny (i.e. sun-exposed) side of the fruit compared to the shady side. For all cultivars, the flavonol index (FLAV) was higher in the sunny side compared with the shady side. The chlorophyll index (CHL) for the shady sides of Granny Smith and Golden Delicious was significantly higher than for the sunny sides. Fine linear regressions were found between the ANTH, FLAV and CHL indices and the actual anthocyanin, flavonol and chlorophyll concentrations, respectively, which were determined destructively on the apple peel extracts. A negative correlation was found between the apple sugar content and the chlorophyll fluorescence in the far-red spectral band. CONCLUSION Our results indicate that a single multiparametric fluorescence-based sensor can provide valuable non-destructive markers of ripening and quality in apples.

Gas exchange, water relations and osmotic adjustment in two scion/rootstock combinations of Prunus under various salinity concentrations

Growth, gas exchange and water relations have been studied on hydroponically grown peach (cv. Armking) plants, grafted on GF677 (Arm/GF) and Mr.S.2/5 (Arm/MrS), exposed to 0, 40, 80 and 120 mM NaCl concentration, over a four-week period. Plant performance was also evaluated during a subsequent four-week period of relief from stress, by supplying the plants with a complete nutrient solution. Salinity stress reduced growth and net assimilation rate to a greater extent in Arm/GF than in Arm/MrS plants. Salt-induced water stress was more severe in Arm/GF than Arm/MrS leaves, and particularly during the first two weeks of treatment. On the other hand, leaf osmotic potential at full turgor (ΨπFT) of salt-treated Arm/MrS received a markedly greater contribution from Na+ and Cl− than salt-treated Arm/GF plants. By contrast, divalent cations and K+ made a substantially greater contribution to leaf ΨπFT of salt-treated Arm/GF than to the corresponding ΨπFT of Arm/MrS plants. Salinity stress markedly altered leaf carbohydrate composition and led to a preferential accumulation of sorbitol, independent on the scion/rootstock combination. Salt-treated Arm/GF but not Arm/MrS plants stored most of the Na+ and Cl− loaded in the shoot, into basal (old) leaves. The rootstock ability to control the accumulation of salt in the scion leaves during the salinity stress, determined striking differences in the recovery of photosynthetic performances, during the relief period. A full recovery of A and gs was detected in both 40 and 80 mM salt-treated Arm/GF leaves, but only in 40 mM salt-treated Arm/MrS, at the end of the relief treatment. These data indicate a greater efficiency of GF677 than Mr.S.2/5 in protecting peach plants from the deleterious effects of NaCl stress.

Variations in physiological and biochemical traits of oak seedlings grown under drought and ozone stress

Despite the huge biodiversity characterizing the Mediterranean environment, environmental constraints, such as high sunlight and high temperatures alongside with dry periods, make plant survival hard. In addition, high irradiance leads to increasing ozone (O3 ) concentrations in ambient air. In this era of global warming, it is necessary to understand the mechanisms that allow native species to tolerate these environmental constraints and how such mechanisms interact. Three Mediterranean oak species (Quercus ilex, Quercus pubescens and Quercus cerris) with different features (drought tolerant, evergreen or deciduous species) were selected to assess their biometrical, physiological and biochemical responses under drought and/or O3 stress (80-100 nl l(-1) of O3 for 5 h day(-1) for 77 consecutive days). Leaf visible injury appeared only under drought stress (alone or combined with O3 ) in all three species. Drought × O3 induced strong reductions in leaf dry weight in Q. pubescens and Q. cerris (-70 and -75%, respectively). Alterations in physiological (i.e. decrease in maximum carboxylation rate) and biochemical parameters (i.e. increase in proline content and build-up of malondialdehyde by-products) occurred in all the three species, although drought represented the major determinant. Quercus ilex and Q. pubescens, which co-occur in dry environments, were more tolerant to drought and drought × O3 . Quercus ilex was the species in which oxidative stress occurred only when drought was applied with O3 . High plasticity at a biochemical level (i.e. proline content) and evergreen habitus are likely on the basis of the higher tolerance of Q. ilex.

Development of autotrophy and tolerance to acclimatization of Myrtus communis transplants cultured in vitro under different aeration

The behaviour of myrtle (Myrtus communis L.) plantlets during the last phase of in vitro culture before transplanting was studied. Myrtle plants were sampled from Mediterranean shrubland vegetation. In vitro growth of myrtle microcuttings was evaluated during the rooting phase using 500 cm3 containers fitted with two different types of closures. The number of gas exchanges and time in which aerated and closed vessels lose half of their gas content were calculated. Both types of vessel closure allowed photosynthetic activity in myrtle cultures even though the higher aeration rate induced higher net photosynthetic rate (PN) during all the culture. In vitro morphogenetic and rooting of myrtle microcuttings were affected by the different environment conditions inside the culture vessels: plantlet growth and root formation of myrtle explants increased in aerated vessels in comparison with closed ones. The well developed root system, the higher PN and dry mass accumulation during the pre-acclimatization phase in aerated vessels induced a better ability to face the transplant stress.

The Effect of Drought on Gas Exchange and Water Potential in Leaves of Seven Mediterranean Woody Species

The water relations and gas exchange parameters of Arbutus unedo, Cistus monspeliensis, Erica arborea, Myrtus communis, Phillyrea latifolia, Pistacia lentiscus, and Quercus ilex growing in the shrubland vegetation at the Parco Naturale della Maremma (Italy), were studied over two consecutive years. At high leaf water potentials, photosynthetic rates and stomatal conductance were relatively low in all species but C. monspeliensis. Stomatal conductance remained relatively high in C. monspeliensis leaves as soil moisture was depleted, whereas A. unedo, E. arborea, M. communis, and P. lentiscus were more conservative in water use. P. latifolia and Q. ilex showed a drought-tolerant behaviour.

Effects of 1-methylcyclopropene and post-controlled atmosphere air storage treatments on fresh-cut Ambrosia apple slices

BACKGROUND The effect of 1-methylcyclopropene (1-MCP) treatment and two different post-controlled atmosphere air storage (PCAAS) durations on the quality and chemistry of fresh-cut Ambrosia apple slices was studied. RESULTS PCAAS for 1 or 2 weeks prior to slicing had an overall positive effect on the resultant quality of fresh-cut apple slices. The most significant responses to PCAAS were the suppression of both phenolic and o-quinone accumulation in slices, and this was related to the significantly lower browning potential values obtained for slices from PCAAS-treated apples. Polyphenol oxidase (PPO), peroxidase (POX) and ascorbate peroxidase (APOX) activities were not affected by 1-MCP or PCAAS treatments. PPO and POX activities were almost completely inhibited by a 50 g L⁻¹ calcium ascorbate anti-browning dip of apple slices from all treatments. CONCLUSION The most dramatic effect of the PCAAS treatments was to reduce the accumulation of soluble phenolics, which is likely the reason that o-quinone accumulation was also inhibited in treated fruits. The consequent reduction in browning potential may be the explanation as to why PCAAS treatment has been shown to reduce fresh apple slice browning in previous work.

The harsh life of an urban tree: the effect of a single pulse of ozone in salt-stressed Quercus ilex saplings

Ozone (O3) and salinity are usually tested as combined factors on plant performance. However, the response to a single episode of O3 in plants already stressed by an excess of NaCl as occurs in the natural environment has never been investigated, but is important given that it is commonly experienced in Mediterranean areas. Three-year-old Quercus ilex L. (holm oak) saplings were exposed to salinity (150 mM NaCl, 15 days), and the effect on photosynthesis, hydric relations and ion partitioning was evaluated (Experiment I). In Experiment II, salt-treated saplings were exposed to 80 nl l-1 of O3 for 5 h, which is a realistic dose in a Mediterranean environment. Gas exchanges, chlorophyll fluorescence and antioxidant systems were characterized to test whether the salt-induced stomatal closure limited O3 uptake and stress or whether the pollutant represents an additional stressor for plants. Salt-dependent stomatal closure depressed the photosynthetic process (-71.6% of light-saturated rate of photosynthesis (A380)) and strongly enhanced the dissipation of energy via the xanthophyll cycle. However, salt-treated plants had higher values of net assimilation rate/stomatal conductance (A/gs) than the controls, which was attributable to a greater mesophyll conductance gm/gs and carboxylation efficiency (higher gm/maximal rate of Rubisco carboxylation (Vcmax)), thus suggesting no damage to chloroplasts. O3 did not exacerbate the effect of salinity on photosynthesis, however a general enhancement of the Halliwell-Asada cycle was necessary to counteract the O3-triggered oxidative stress. Despite the 79.4% gs reduction in salt-stressed plants, which strongly limited the O3 uptake, a single peak in the air pollutant led to an additional burden for the antioxidant system when plants had been previously subjected to salinity.

A Spectroscopy-Based Approach for Automated Nondestructive Maturity Grading of Peach Fruits

This paper presents an automated approach for peach fruit maturity grading that, by exploiting fiber-optic spectroscopy-based sensors and multivariate processing techniques, minimizes the operator intervention while reducing discharge and waste. The use of a spectroscopic sensor complies with the so-called nondestructive measurement method, which enables fast repeated measurements to be performed at the single fruit level while avoiding fruit damage and loss. Maturity grading is accomplished by retrieving estimates of the fruit flesh firmness by means of multivariate retrieval techniques applied to the reflectance spectra acquired with the spectrometer and by processing the retrieved values within the framework of a maturity fuzzy classifier. A decision support system is developed to provide the user with maturity category decision and associated reliability. Experimental results show that the approach is effective for automated maturity grading of peach fruits affected by a high degree of variability. This paper lays the foundations for the realization of easy-to-use sustainable automated maturity grading systems.