Water shortage and quality of fleshy fruits—making the most of the unavoidable

Abstract

Extreme climatic events, including drought, are predicted to increase in intensity, frequency, and geographic extent as a consequence of global climate change. In general, to grow crops successfully in the future, growers will need to adapt to less available water and to take better advantage of the positive effects of drought. Fortunately, there are positive effects associated with drought. Drought stimulates the secondary metabolism, thereby potentially increasing plant defences and the concentrations of compounds involved in plant quality, particularly taste and health benefits. The role of drought on the production of secondary metabolites is of paramount importance for fruit crops. However, to manage crops effectively under conditions of limited water supply, for example by applying deficit irrigation, growers must consider not only the impact of drought on productivity but also on how plants manage the primary and secondary metabolisms. This question is obviously complex because during water deficit, trade-offs among productivity, defence, and quality depend upon the intensity, duration, and repetition of events of water deficit. The stage of plant development during the period of water deficit is also crucial, as are the effects of other stressors. In addition, growers must rely on relevant indicators of water status, i.e. parameters involved in the relevant metabolic processes, including those affecting quality. Although many reports on the effects of drought on plant function and crop productivity have been published, these issues have not been reviewed thus far. Here, we provide an up-to-date review of current knowledge of the effects of different forms of drought on fruit quality relative to the primary and secondary metabolisms and their interactions. We also review conventional and less conventional indicators of water status that could be used for monitoring purposes, such as volatile compounds. We focus on fruit crops owing to the importance of secondary metabolism in fruit quality and the importance of fruits in the human diet. The issue of defence is also briefly discussed.

Kaolin and salicylic acid foliar application modulate yield, quality and phytochemical composition of olive pulp and oil from rainfed trees

“…Stress conditions influence the metabolism of phenolic compounds in fruits, mainly in two ways, which are not mutually exclusive and that may even interact. First, due to the reduction in net photosynthesis that may result in a decrease in carbohydrate supply to the fruits, the major source of precursors for the biosynthesis of these phytochemicals; second, the stress conditions may exacerbate the oxidative stress, promoting the biosynthesis of this group of antioxidant compounds (Ripoll et al, 2014;Wang and Frei, 2011). To notice, phenolic compounds accumulate more, both in fruits and olive oil, in 2016 than in 2015 harvest (Tables 3 and 4).…”

Impact of water quality and irrigation management on organic greenhouse horticulture

“…The effects of water deficit on cell size and cell turgor may also impact quality attributes. Indeed, a positive relationship between tomato fruit dry matter or total soluble solids and firmness was observed, although conflicting results between moderate water stress and firmness were reported (Ripoll et al 2014).…”

“…These are all important taste attributes (Ripoll et al 2014). However, organic acids may not be positively affected by water deficit in some species, such as strawberry.…”

Drought-stressed tomato plants trigger bottom-up effects on key mite pests

“…An alternative explanation for the reduction of some digestive protease and α-amylase activities in T. evansi could be related to the higher availability of nutrients in a readily assimilated form (essential amino acids and free sugars) in tomato plants subjected to drought conditions. Tomato plants are known to induce an array of secondary metabolites during periods of water deficit (Ripoll et al, 2014), thereby potentially increasing the concentration of compounds involved in plant defense. However, no significant changes in esterase, GST or P450 specific activities were observed when T. evansi was fed on drought-stressed plants.…”

“…However, water deficit stress in tomato plants had been reported to increase some of these plant defenses, such as protease inhibitors and the oxidative enzymes polyphenol oxidases and peroxidases (English-Loeb et al, 1997;Inbar et al, 2001;Ripoll et al, 2014). On the other hand, water deficit stress can elicit accumulations of nutrients in tomato plants.…”