Fernando Malorgio

Effects of Salinity Stress on Carotenoids, Anthocyanins, and Color of Diverse Tomato Genotypes

One nonanthocyanin-accumulating (Ailsa Craig) and three anthocyanin-accumulating tomato genotypes (Anthocyanin fruit type, Atroviolaceum, and Sun Black) were analyzed to assess differences in their carotenoid and anthocyanin levels and color and to evaluate the effects of nutrient solutions with different salt concentrations on these parameters. The carotenoid content of control Atroviolaceum tomatoes was ca. 2-2.5-fold higher relative to the other two types, and the color of its puree could be visually distinguished from those of other genotypes. Salinity stress led in some cases to a 2-3-fold increase in the lycopene content. Saline treatment increased the accumulation of total anthocyanins in fruits of Sun Black (2-fold increase), while it reduced it in fruits of Anthocyanin (10-fold decrease). In general, the treatment increased the differences in color of different purees. These results indicate that salinity stress can lead to similar or higher increases in tomato carotenoids than those achieved by genetic engineering. In addition, these changes were accompanied by visually discernible color differences in tomato products. Our findings show the considerable potential of exploiting saline soils to obtain tomatoes with higher levels of secondary metabolites like carotenoids and anthocyanins.

Root Zone Sensors for Irrigation Management in Intensive Agriculture

Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy.

Growth and photosynthesis of Lycopersicon esculentum (L.) plants as affected by nitrogen deficiency

Fully expanded leaves of tomato (Lycopersicon esculentum) growing with either complete or nitrogen-deficient nutrient solution were analysed for leaf water status, gas exchange and chlorophyll fluorescence during the vegetative and reproductive phases. N-deficiency did not affect leaf water relations but did decrease light saturated photosynthetic rate as well as stomatal conductance in the vegetative stage. A lower variable to maximum fluorescence ratio (Fv/Fm) was found in N-limited plants which also showed an increase in leaf starch content and in starch to sucrose ratio. The inhibition of photosynthesis and the alteration of photosynthates partitioning were responsible for the growth reduction in N-stressed plants. During the reproductive phase the limitation of photosynthesis may be due to a large accumulation of starch which determines both a decrease in the carbon demand from the sinks and a decrease in CO2 conductance in the mesophyll.

Modeling Salinity Build-Up in Recirculating Nutrient Solution Culture

Abstract This paper presents a simple model for the changes in ion concentration and electrical conductivity (EC) of the recirculating nutrient solution in a closed-loop soilless culture of tomato (Lycopersicon esculentum Mill.). The model was designed on the basis of a balanced equation for plant nutrient uptake: for macrocations (K+, Mg2+ and Ca2+), a linear dependence of concentration on crop water uptake was assumed, while for non-essential ions, such as sodium (Na+), a non-linear function was used. The model was developed for closed-loop hydroponic systems in which crop water uptake (namely, transpiration) is compensated by refilling the mixing tank with complete nutrient solution. In these systems, EC gradually increases as a result of the accumulation of macro-elements and, principally, of non-essential ions, like Na+, for which the apparent uptake concentration (i.e., the ratio between nutrient and water uptake) is lower than their concentration in the irrigation water. For model calibration, data from both the literature and a previous work were used, while validation was performed with data from original experiments conducted with tomato plants in different seasons and using water with different sodium chloride (NaCl) concentrations (10 and 20 meq/L). The results of validation indicate that the model may be a useful tool for the management of closed-loop hydroponics, because it simulates rather well the salt accumulation that occurs in the recirculating nutrient solution when it is prepared with irrigation water of poor quality. Furthermore, the model is able to estimate the amount of crop evapotranspiration that leads to a value of EC at which flushing is necessary, thus enabling one to predict the water and nitrogen runoff of the semi-closed soilless culture.

Empirical Models of Macronutrient Uptake in Melon Plants Grown in Recirculating Nutrient Solution Culture

Abstract The article presents a number of empirical models for predicting the macronutrient uptake of melon plants grown in nutrient film technique under environmental conditions of plastic greenhouse in the Mediterranean region. Models were developed according to two statistical procedures: stepwise multiple regression (MR) and canonical correlation (CC). Independent variables considered by the modeling were global radiation and air temperature in the greenhouse, crop age (expressed as number of weeks from planting, growing degree days and photo-thermal units), and the uptake of water as well as of a guide-ion that could be routinely measured manually by means of easy-to-use test-kits or automatically with chemo-sensors. The best models, as selected on the basis of determination coefficient and the correlation coefficient for the relationship between residuals and observations, explained only 36–72% of the variance in the mineral uptake, depending on the considered nutrient. Moreover, the models were conservative, as predicted values tended to be less extreme with respect to the observed values and the residuals were positively correlated to the observations. The results of MR and CC were similar, although the validation of the models derived from CC produced better results compared to MR. The models provided evidence for the close relationship between ion and water uptake and indicated the possibility to predict the crop mineral requirements on the basis of the consumption of a guide-ion (i.e., nitrogen).

Uptake and distribution of selenium in tomato plants as affected by genotype and sulphate supply

Abstract Aim of this work was to investigate if the variation among tomato genotypes in selenium (Se) uptake and accumulation observed in short term experiments are maintained over longer growth periods and if there is a positive correlation in shoot between sulphur (S) accumulation and Se accumulation across different genotypes or if higher tissue S results in greater feedback inhibition of Se uptake. Two experiments were carried out under greenhouse conditions and different genotypes of Lycopersicon lycopersicum (UC82B and LA2711), Lycopersicon pennellii (LA716) and Lycopersicon peruvianum (LA2157) were grown until fruit ripening. The results obtained in the two experiments confirmed that sulphate in the growth solution reduced selenate uptake by plants and increased the S content of the leaves. Under low sulphate treatment there was a clear correlation (R2=0.82) between leaf S content and shoot Se content across genotypes in both experiments, indicating that the overall activity of the S transport syst...

A comparison between two methods to control nutrient delivery to greenhouse melons grown in recirculating nutrient solution culture

Abstract Two methods to control nutrient delivery to greenhouse melon plants grown with the nutrient film technique were compared: a conventional control system based on the adjustment of electrical conductivity (EC) of the recirculating nutrient solution, and a programmed nutrient addition, which was based simply on pre-established weekly supply of N, P and K without any attempt to maintain constant values of nutrient concentration and EC. The method to control nutrient supply did not influence significantly fruit yield or quality, but the nutrient addition reduced the crop consumption of water, N, P and K by 40–60% with respect to the EC method.

Salt tolerance and mineral relations for celery

Abstract To invertigate the relationship between salt tolerance and plant mineral status in celery (Apium graveolens L.) growth and the concentration of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), and chloride (Cl) in different tissues were determined in plants grown in hydroculture with nutrient solutions containing 5 (control), 50,100, and 300 mM sodium chloride (NaCl) for four weeks. At salinity levels of 50 and 100 mM NaCl, there was a moderate, albeit significantly, reduction of growth, while a drastic decrease in both fresh and dry weight was obtained at 300 mM NaCl. Regardless of the salinity level, growth resumed promptly and completely once the stress was ceased. Sodium chloride stress reduced the accumulation of nitrate (NO3)‐N in all plant tissues, but there were no relevant effects on the concentration of reduced N and P. The concentration of K in roots and leaf petioles was unaffected by NaCl treatment, but it gradually declined with increasing salinity in leaf bla...

The influence of growing season on fruit yield and quality of greenhouse melon (Cucumis melo L.) grown in nutrient film technique in a Mediterranean climate

Summary The influence of growing season on some physiological and biochemical variates related to fruit yield and quality was investigated in melon (Cucumis melo L.) plants cultivated in nutrient film technique in a greenhouse located at Pisa, Central Italy, from mid-March to mid-June, or from mid-July to mid-September. Compared with spring, the plants grown in summer exhibited faster growth and development, but produced fewer fruits of larger size and poorer quality due to reduced sucrose content. Growing season did not affect total leaf area, but dry-matter production and partitioning to the fruits was significantly lower in summer than in spring. Summer fruit ripened within 30–35 d after anthesis, about 14 d fewer than in spring. Higher average temperature was presumably responsible for earlier fruit maturation in summer, as in both seasons all melons were harvested after 450–500 degree-days (base temperature of 12°C) from anthesis. Fruit swelling did not account for the reduction of sucrose content in summer-grown fruits, which instead was due to shortage of photoassimilate supply and inadequate sucrose synthesis, as suggested by the rate of leaf gas exchange and the activity of sucrose phosphate synthase in the fruit flesh, as determined during the final stages of fruit development. Lower solar radiation was presumably responsible for the reduced leaf carbon assimilation in summer, as growing season did not affect leaf turgor, stomatal conductance, mineral status and chlorophyll content.

Brassica juncea can improve selenite and selenate abatement in selenium contaminated soils through the aid of its rhizospheric bacterial population

Brassica juncea was grown in a soil spiked with selenium oxyanions (selenite and selenate) in order to verify the contribution of both plants and rhizospheric bacteria to the abatement of soluble forms of the metalloid. A mass balance of selenium was calculated in pots and the different chemical species of this contaminant were measured. Evidence gained suggests that selenium oxyanions were reduced into less bioavailable forms thank to a marked contribution of the soil bacterial population. Rhizobacteria resulted particularly elicited by the presence of B. juncea which directly participated in selenium decontamination through either phytoextraction or putative volatilisation. Moreover, these microbes colonizing B. juncea root system were monitored by both culture dependent and culture independent methods (i.e. DGGE analysis). Finally, bacterial isolates were tested in vitro for their resistance to selenium oxyanions.