Fruit Crops Physiology and Nutrition

Fruit crops are among the most intensive agricultural systems in terms of inputs of pesticides and fertilizers, as well as investments in capital and material [1]. However, it is known that perennial crops, such as fruit, have been shown to have energy use, soil erosion, and nitrogen loss rates of less than 5% of the rates of annual crops [2]. The financial benefits of fruit crops are associated with their high yields of very valuable and unique human food products. Fruits are a major source of nutrients and bioactive compounds such as antioxidants [3]. While the genotype of cultivated plants prescribes their production potential, the degree to which these genetic potentials are realized varies depending on the environmental factors that influence the growth metabolism in different ways and ultimately determine vegetation and fruiting [4]. The amounts and ratios of the available inorganic nutrients, in proportion to the needs of the crops at the various phases of development, are factors that can and should be continuously managed [5,6]. It is evident that the application of fertilizers cannot be a straightforward routine task but rather a synthesis of knowledge, experience, and modern technology. Since these are perennial crops, their root layer depth makes it difficult to control and study them in detail, due to the influence of numerous factors that alter the physiology of nutrition each year [7]. The above points demonstrate the importance of understanding the nature of fruit trees’ nutrition problems, as well as the need for continuous information on scientific advances, to enable their prevention and timely treatment [8].

Undoubtedly, important progress has been made in recent decades in understanding the mechanisms of nutrient uptake and their functions in plant metabolism [9,10]. At the same time, there have also been advances in increasing crop yields by supplying mineral nutrients through fertilizer application [11].

The Special Issue “Fruit Crops Physiology and Nutrition” therefore sheds light on some aspects of this multifactorial topic and contributes to its better understanding.

This Special Issue includes five research papers in which different issues of fruit physiology and nutrition are investigated. Τhe papers aim toward the following:

(a)

To gain insight into how cultivation practices (organic vs. integrated) affect the fruit quality (physiological, organoleptic, and phytochemical attributes) and plant nutrition of two apricot cultivars [12]. As is known, conventional, organic, and integrated agriculture are the basic cultural management practices used in the production of foods [13,14]. The results show that the factor “cultivar” had the largest effect on the variables that were measured, and that the factor “farm” also had a significant impact within each cultivation management. The results suggest that there are so many variables that affect the results of a particular cultivation practice that it is difficult to draw general conclusions about which practice is the best. Therefore, the authors state that more research is needed.

(b)

To assess the suitability of alternative nutrient sources/substrates for potted olives [15]. Today, the growth substrate of potted plants is generally based on rather expensive peat mixed with inorganic materials [16]. However, the European Commission in 2001 excluded the issuance of the European ‘Eco-label’ for plants produced with growth substrates containing peat [17]. Moreover, the rapid depletion of peat lands and the consequent environmental concern have led producing countries to limit the exploitation of this natural resource [18]. Therefore, attention to the replacement of peat in growth substrates is increasing. Along these lines, this article reveals that the best performance was recorded in plants grown in a substrate combining sheep manure and litter from evergreen broadleaf species. However, they propose that, in order to obtain more definite findings on the advantageous effects of organic amendments on the nutrition and physiology of olive trees, multi-year field research is required.

(c)

To increase the knowledge of the impacts of salinity stress on pomegranate and strawberry and/or examine ways to alleviate it [19,20]. The negative effects caused by salinity on crops can be mainly summarized in terms of two factors: the osmotic effect and the toxic effect, although in some cases, nutritional alterations can be also observed [21,22]. Dichala et al. [19], experimenting on three pomegranate cultivars that were subjected to salinity stress, suggested that tolerant cultivars are able to exclude salts from the roots [23]; moreover, they have an internal mechanism of tolerance. On the other hand, several approaches have been taken to mitigate the negative effects of salinity on plants, including the use of glycine betaine [24] and microorganisms [25]. In addition, natural zeolites are used as inorganic soil conditioners and are commonly used in agriculture as a silicon source to improve the growth and yield of crops’ productivity under normal or stressful conditions [26,27]. Thus, several studies have mentioned that zeolite can mitigate salt damage in plants [28,29]. Similarly, bentonite has not been tested as extensively, but reports present its beneficial effects on plant growth under salinity stress [30]. In accordance, Ntanos et al. [20] suggested that glycine betaine applied foliarly and a bentonite—zeolite mixture added to the substrate proved to alleviate salinity stress in strawberry plants.

(d)

To address the possibility of alleviating cracking in figs at harvest [31]. Figs (Ficus carica L.) are soft fruits highly susceptible to fruit skin-side cracking and ostiole-end splitting during growth and development [32]. Some plant hormones, such as salicylic acid, have shown positive effects on the fruit quality and the extension of the shelf life [33,34,35]. Herein, the researchers Karantzi et al. [31] concluded that foliar salicylic acid seems to be an inexpensive environmentally friendly agent that enhances the quality and marketability of fig fruit while also making fig harvesting and postharvest handling easier.

The Editor of this Special Issue would like to thank all the authors who accepted invitations and provided their valuable contributions. The Editor is also thankful to MDPI for the collaboration.