Shading Affects Yield, Elemental Composition and Antioxidants of Perennial Wall Rocket Crops Grown from Spring to Summer in Southern Italy.

Gianluca Caruso,Eugenio Cozzolino,Alessio Tallarita,Christophe El-Nakhel,Stefania De Pascale,Vincenzo Cenvinzo,Luigi Formisano,Antonio Pannico,Youssef Rouphael

doi:10.3390/plants9080933

Gianluca Caruso, Eugenio Cozzolino + Show 7 more

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https://doi.org/10.3390/plants9080933

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Abstract

Shading nets have been increasingly drawing research interest, as they allow us to improve the environmental conditions for greenhouse-grown crops. The effects of two shading nets (50% and 79% shading degree), plus an unshaded control, on yield, mineral composition and antioxidants of perennial wall rocket (Diplotaxis tenuifolia L.-D.C.) grown under tunnels in southern Italy were determined. The shading application resulted in a yield decrease, compared to the unshaded control, except for the highest production under 50% shading in July. The highest yield was recorded in the April–May and May–June and the lowest in July. Similar trends were recorded for plant dry weight, leaf number per rosette and mean weight, but the latter showed the highest value under 79% light extinction in July. The rocket leaves were brighter in the summer cycles than in the spring ones. Leaf nitrate was highest in spring and under 79% shading. Potassium, phosphorus, calcium and magnesium showed the highest values in spring and in the unshaded control. The lipophilic antioxidant activity showed the highest values under the 79% shading net in the spring cropping seasons, whereas in July it did not significantly differ from 50% light extinction. The hydrophilic antioxidant activity always attained the highest values in the unshaded control. The unshaded leaves had the highest total phenol accumulation when grown in April–May and the lowest in July. The total ascorbic acid content was always highest in the unshaded control leaves compared to the shading treatments. Fifty percent crop shading is, therefore, an effective sustainable tool for increasing the yield of perennial wall rocket leaves in July, when the light intensity under the plastic tunnel exceeds the plant requirements, also resulting in a mineral composition that is not significantly different from that of the unshaded crops.

Highlights

Diplotaxis tenuifolia L., commonly named perennial wall rocket, is spread worldwide, oriented both to the fresh salad market and the baby leaf industry [1], appreciated by consumers for its bitter flavor, and rich in beneficial phytonutrients such as vitamin C, glucosinolates and flavonoids [2].Plants 2020, 9, 933; doi:10.3390/plants9080933 www.mdpi.com/journal/plantsPerennial wall rocket needs proper levels of light intensity and air temperature to encourage plant growth as well as leaf yield and phytochemical content [3,4,5]
Cropping seasons in the unshaded control, which was 2.84-fold and 4.32-fold higher on average compared to 50% and
The shading application resulted in a yield decrease, compared to the unshaded control, over the first three cycles from April to the end of June, whereas the crops grown in July showed a production increase under 50% shading (Figure 2a); 79% light extinction always caused the worst performance, but in April–May it did not significantly differ from the May–June cropping season

Summary

Introduction

Perennial wall rocket needs proper levels of light intensity and air temperature to encourage plant growth as well as leaf yield and phytochemical content [3,4,5]. In order to modulate the aforementioned environmental factors, different strategies can be adopted, among which are the use of shading nets, which can contribute to improving the plant growing conditions, leading to more vigorous plants, higher yields and better quality produce [6,7]. Shading nets are characterized by different mechanical, physical and optical properties [8], which allow for the modulation of light and temperature levels around crops. The photoselective screens increase the diffused radiation, normalize excessive levels of light, temperature, humidity and wind velocity [12] which allow for the greater efficiency of vegetable production in protected cultivation [13]. Photoselective nets improve the quality of vegetables at harvest [14] and at the post-harvest stage [15,16,17]

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