Simona Proietti

Yield, water requirement, nutrient uptake and fruit quality of zucchini squash grown in soil and closed soilless culture

Summary The effects of soil and closed soilless systems (cocofibre, perlite and pumice culture) on precocity, productivity, water use, plant mineral composition and fruit quality were studied on zucchini plants (Cucurbita pepo L. ‘Afrodite’ grown in a greenhouse at Viterbo, central Italy. The plants grown in a soilless system exhibited higher yield (total, marketable and fruit number), harvest index, and water-use efficiency compared with those grown in soil. Among soilless treatments, pumice had the lowest water requirement and hence the highest water use efficiency. Use of cocofibre led to the earliest yield compared with the other substrates due probably to the higher minimal temperatures recorded on the organic substrate. Plants grown in soilless culture had a higher uptake of N, Mg, Na, Fe, Cu, Mn, Zn than those grown in soil. After 73 d of solution recycling in soilless treatments, N-NO3, K, P, Fe and Mn were depleted by 26, 16, 40, 92, and 25% respectively, while Ca, Mg, Na, Cu and Zn increased by 6, 69, 113, 360, and 981 % respectively. Carbohydrate concentration (glucose, fructose, sucrose and starch) increased in soilless over soil culture. No significant differences were observed in dry matter or total protein content. Nitrate concentration of fruits was lower in soil than in soilless treatments. The results demonstrated that the growers may improve water and nutrient control, yield and fruit quality by switching from soil to closed soilless culture.

Increase of ascorbic acid content and nutritional quality in spinach leaves during physiological acclimation to low temperature

The effect of acclimation to 10 degrees C on the leaf content of ascorbic and oxalic acids, was investigated in spinach (Spinacia oleracea L.). At 10 degrees C the content of ascorbic acid in leaves increased and after 7 days it was about 41% higher than in plants remaining under a 25 degrees C/20 degrees C day/night temperature regime. In contrast, the content of oxalate, remained unchanged. Transfer to 10 degrees C increased the ascorbic but not the oxalic acid content of the leaf intercellular washing fluid (IWF). Oxalate oxidase (OXO EC 1.2.3.4) activity was not detected in extracts of leaf blades. Therefore, oxalic acid degradation via OXO was not involved in the control of its content. Our results show that low temperature acclimation increases nutritional quality of spinach leaves via a physiological rise of ascorbic acid that does not feed-forward on the content of oxalic acid.

The effect of growing spinach (Spinacia oleracea L.) at two light intensities on the amounts of oxalate, ascorbate and nitrate in their leaves

Summary The effect of growing spinach at two light intensities on the content of oxalate, ascorbate and nitrate in their leaves was determined. Plants were grown for five weeks in a growth cabinet under a 10 h light/14 h dark photoperiod and a photon flux density of either 800 or 200 µmol quanta m–2 s–1. The content of oxalate, ascorbate and nitrate in the fourth and fifth fully expanded true leaves was then determined at three times during the photoperiod. Spinach plants grown at the lower light intensity showed decreased growth, a decreased leaf area per plant and an increased shoot to root ratio. Leaves from plants grown under low light contained less ascorbate but more oxalate and nitrate. Our data show that the nutritional quality of spinach is thereby decreased by growth in low light intensities and suggest that the content of oxalic acid in leaves may depend on the rate of its catabolism.

Thidiazuron increases current-year fruit size and production in Actinidia deliciosa without decreasing return bloom

Summary The effects of whole-crown application of thidiazuron (TDZ), applied two weeks after full bloom, at the concentrations of 0 (control), 2 or 10 ppm, on vine yield, fruit quality and on next-season potential yield of Actinidia deliciosa ‘Hayward’ were evaluated in 1998–99. Fruit growth increased rapidly after TDZ application. Fruit fresh weight and yield increased by about 13% and 22% with the 2 and 10 ppm concentration, respectively. These responses were associated with only small changes in fruit shape, with 10 ppm-treated fruits slightly rounder than the control. During ripening, TDZ did not affect fruit soluble solid content, flesh firmness or concentration of non-structural carbohydrates. No effect was observed on the amount of winter pruning, entity of bud burst, percent of fertile buds, number of inflorescences per fertile bud or percent of vegetative buds. These results show that TDZ can be applied to the whole crown to increase fruit size and yield, without affecting fruit quality or the next-season’s crop.

Peach leaf curl disease shifts sugar metabolism in severely infected leaves from source to sink.

Peach leaf curl is a disease that affects the leaves of peach trees, and in severe cases all of the leaf can be similarly affected. This study investigated some effects of this disease on the metabolism of peach leaves in which all parts of the leaf were infected. These diseased leaves contained very little chlorophyll and performed little or no photosynthesis. Compared to uninfected leaves, diseased leaves possessed higher contents of fructose and especially glucose, but lowered contents of sucrose, sorbitol and especially starch. The activities of soluble acid invertase, neutral invertase, sorbitol dehydrogenase and sucrose synthase were all higher in diseased leaves, whereas, those of aldose-6-phosphate reductase and sucrose phosphate synthase were lower. The activities of hexokinase and fructokinase were little changed. In addition, immunblots showed that the contents of Rubisco and ADP-glucose phosphorylase were reduced in diseased leaves, whereas, the content of phosphoenolpyruvate carboxylase was increased. The results show that certain aspects of the metabolism of diseased leaves are similar to immature sink leaves. That is photosynthetic function is reduced, the leaf imports rather than exports sugars, and the contents of non-structural carbohydrates and enzymes involved in their metabolism are similar to sink leaves. Further, the effects of peach leaf curl on the metabolism of peach leaves are comparable to the effects of some other diseases on the metabolism of photosynthetic organs of other plant species.

Rocket seedling production on the international space station: Growth and nutritional properties

Producing sprouts directly during space missions may represent an interesting opportunity to offer high-quality fresh ready to eat food to the astronauts. The goal of this work was to compare, in terms of growth and nutritional quality, rocket (Eruca sativa Mill.) seedlings grown in the International Space Station during the ENEIDE mission with those grown in a ground-based experiment (in presence and absence of clinorotation). The rocket seedlings obtained from the space-experiment were thinner and more elongated than those obtained in the ground-based experiment. Cotyledons were often closed in the seedlings grown in the space experiment. Quantitative (germination, fresh and dry weight) and qualitative (glucose, fructose, sucrose and starch) traits of rocket seedling were negatively affected by micrograv-ity, especially those recorded on seedlings grown under real microgravity conditions The total chlorophyll, and carotenoids of seedlings obtained in the space experiment were strongly reduced in comparison to those obtained in the ground-based experiment (presence and absence of clinorotation). The results showed that it is possible to produce rocket seedlings in the ISS; however, further studies are needed to define the optimal environmental conditions for producing rocket seedlings with high nutritional value

Late summer photosynthesis and storage carbohydrates in walnut (Juglans regia L.): Feed-back and feed-forward effects

The effect of late summer - autumn limitation of phloem export on growth, photosynthesis and storage carbohydrate accumulation, was evaluated in walnut (Juglans regia L.). This was done by girdling current years shoots, with either all or with only a third of the leaves left in place. Nineteen days after girdling, photosynthesis was greatly reduced and after 46 days, it was about 70% lower in both girdling treatments compared to the control (ungirdled shoots). This reduction is consistent with a feed-back effect of an increased carbohydrate content of the leaves. At the end of the experiment (46 days after girdling), the radial growth of girdled shoots was increased at their base but not at their apical part compared to the control. Girdling increased the accumulation of sucrose in the bark at the base of the shoot and of starch in the bark and in the wood of the shoot apical part. The activity of ADP-glucose pyrophosphorylase in wood increased in the apical part of girdled shoots. The results suggest that a high availability of carbohydrates elicits a feed-forward action on the shoot sink size and activity (radial growth and storage carbohydrate accumulation). Further, for the first time in tree wood we found an increased total activity of AGP induced by an increased assimilate availability. Moreover, the results indicated that, in late summer - autumn, CO2 uptake by leaves of the deciduous tree walnut is strongly dependent on export of photosynthates from the crown. Therefore, carbon uptake in this period depends largely on the availability of effective storage sinks where newly produced assimilates can be accumulated.