Horticulturae — Open Access Journal

Use of light emitting diode (LED) technology is beginning to replace traditional lighting in greenhouses. This research focused on the effects of LED lighting and gibberellic acid supplementation on growth and flowering of Dahlia spp. ‘Karma Serena’, Liatris spicata ‘Kobold’, and Lilium asiatic ‘Yellow Cocotte’. Light treatments, used to extend photoperiod, included LED flowering lamps and halogen lamps that emitted a combination of red + far-red + white, red + white, and broad spectrum from late fall to early spring. Gibberellic acid treatments ranged from 40 to 340 mg L⁻¹ for Asiatic lily ‘Yellow Cocotte’, 50 to 250 for gayfeather ‘Kobold’, and 50 to 150 for dahlia ‘Karma Serena’. Results varied within species in response to light and gibberellic acid. A significant interaction of light with gibberellic acid influenced mean flower number and flowering percentage for dahlia ‘Karma Serena’, while flowering percentage and flower diameter were influenced for Asiatic lily ‘Yellow Cocotte’. Effect of light was most significant on growth and flowering measurements, especially for gayfeather ‘Kobold’ and dahlia ‘Karma Serena’. For gayfeather ‘Kobold’, flowering occurred two weeks earlier under sole LED lighting than under other light treatments and no supplemental light. Although flowering occurred the earliest for dahlia ‘Karma Serena’ under no supplemental light, plants under light treatments had greater height, width, and shoot weight. Significant effects of gibberellic acid on growth and flowering measurements for dahlia ‘Karma Serena’ and Asiatic lily ‘Yellow Cocotte’ were observed for height, width, and flower number. Full article

Lettuce is a cool season vegetable often produced in greenhouses and other protective structures to meet market demands. Greenhouses are being increasingly adopted in warm climate zones where excessive heat often leads to physiological disorders of lettuce, such as tipburn and premature bolting. Greenhouse lettuce growers in warm climates need cultivar recommendations that can help improve production without ignoring marketability. In the current study, eighteen lettuce cultivars were grown in deep water culture and evaluated for growth, bolting, and tipburn in a greenhouse in Auburn, AL, starting on 30 June and 19 August 2016. Based on the severity of bolting and tipburn, nine cultivars were then selected and evaluated on 17 November 2016 for sensory attributes and marketability by 50 untrained consumer panelists. Cultivars ‘Adriana’, ‘Aerostar’, ‘Monte Carlo’, ‘Nevada’, ‘Parris Island’, ‘Salvius’, ‘Skyphos’, and ‘Sparx’ were selected as having higher heat tolerance than cultivars ‘Bambi’, ‘Buttercrunch’ ‘Coastal Star’, ‘Flashy Trout Back’, ‘Green Forest’, ‘Green Towers’, ‘Jericho’, ‘Magenta’, and ‘Truchas’. Higher crispness, lower bitterness, higher overall texture, and higher overall flavor each correlated to higher marketability, regardless of cultivar, but the strongest predictor of marketability was overall flavor. Overall flavor and overall texture were more strongly correlated to marketability than bitterness and crispness, respectively, suggesting that broader sensory categories may better capture human sensory perceptions of lettuce than narrower categories. Cultivars ‘Aerostar’, ‘Monte Carlo’, ‘Nevada’, ‘Parris Island’, ‘Rex’, ‘Salvius’, and ‘Sparx’ performed well in a hot greenhouse and were preferred by consumers. This step-wise experiment could be an adaptable tool for determining highest performing cultivars under any given production constraint, without ignoring marketability. Full article

This study examined how abscisic acid (ABA) and calcium (Ca) concentrations in nutrient solution affect concentrations of mineral nutrients in tomato leaves and fruit. Tomato plants were grown in a greenhouse at 25/20 °C (day/night) under a 16 h photoperiod. Plants were treated with different concentrations of ABA and Ca. Calcium was applied via the irrigation lines at 60, 90, or 180 mg·L⁻¹. ABA was applied as a combination of foliar sprays and root applications. For foliar ABA applications, treatments consisted of deionized (DI) water control (0.0 mg·L⁻¹ ABA) or 500 mg·L⁻¹ ABA. For ABA root applications, treatments consisted of no ABA control (0.0 mg·L⁻¹ ABA) or 50 mg·L⁻¹ ABA applied via the irrigation lines. Results indicate that mineral nutrient concentrations in tomato leaf and fruit tissue varied in connection with each exogenous application of ABA. Variability in mineral nutrient concentration depended on if ABA was applied to the leaf or root tissue. Additionally, increasing Ca treatment concentrations either decreased or did not change mineral nutrients in tomato and fruit tissue. Thus, tomato plants react to acquiring mineral nutrients in numerous mechanisms and, depending on how the applications of exogenous ABA are applied, can have varying effects on these mechanisms. Full article

Matrix-assisted laser-desorption and ionization time-of-flight mass spectroscopy (MALDI-TOF MS) is a flexible technique for the analysis of protein-containing biological samples. Simple and inexpensive methods have previously been developed for MALDI-TOF MS sample preparation that are able to discriminate between Impatiens species that are closely related and also between regional biotypes of the invasive weed Impatiens glandulifera (Himalayan balsam) with leaf material and also seed material. The current article investigates whether MALDI-TOF MS, through acid-soluble protein ‘fingerprinting’, can be used to analyze plant seeds that result from intensive commercial plant-breeding activity. As an initial proof-of-concept study, tomato seeds from eleven seed-catalogue varieties (F1 Pink Baby Plum, F1 Fantasio, F1 Lizzano, F1 Sungold, F1 Tumbler, Faworyt, Golden Sunrise, Hundreds and Thousands, Indigo Rose, Moneymaker, and Red Alert), listed as Solanum lycopersicum or under the synonym Lycopersicon esculentum were analyzed using MALDI-TOF MS. Whilst peak-rich and highly-reproducible spectra were obtained, with very high Bruker comparison scores and low MALDI-TOF MS variance, sample-preparation variance, and seed-to-seed variance, the spectral differences between varieties were only slightly greater than the above combined variances, indicating very close similarity between all eleven varieties studied. These results are discussed in comparison with those previously observed with the naturally-evolving invasive species I. glandulifera. Full article

In many parts of the world, the agricultural sector is faced with a number of challenges including those arising from abiotic environmental stresses which are the key factors responsible for most reductions in agrifood production. Crude oil contamination, an abiotic stress factor and a common environmental contaminant, at toxic levels has negative impacts on plants. Although various attempts have been made to demonstrate the impact of abiotic stresses on crops, the underlying factors responsible for the effects of crude oil and its induced abiotic stresses on the composition of the stressed plants are poorly understood. Hence, this review provides an in-depth examination of the: (1) effect of petroleum hydrocarbons on plants; (2) impact of abiotic environmental stresses on crop quality; (3) mechanistic link between crude oil stress and its induced abiotic stresses; as well as (4) mode of action/plant response mechanism to these induced stresses. The paper clearly reveals the implications of crude oil-induced abiotic stresses arising from the soil-root-plant route and from direct application on plant leaves. Full article

Water scarcity in many semi-arid agricultural areas, in particular for the Mediterranean basin, is promoting changes in irrigated agriculture, with alternative strategies being introduced for water-use optimization. The coast of Granada and Malaga (Southeast Spain) is an economically important area for subtropical fruit cultivation. This intensively irrigated agriculture is characterized by requiring extra amounts of water and the adoption of sustainable practices to improve agricultural water management. A two-season experiment was conducted to assess (1) the water use in terraced cherimoya (Annona cherimola Mill. cv. Fino de Jete) orchards under conventional and organic production systems with drainage lysimeters, and (2) the impact on fruit yield and nutritional effects between the two considered production systems. Crop coefficient (Kc) values for cherimoya were 0.60–0.66, 0.64–0.71, and 0.48–0.62 at flowering, fruit set, and fruit growth, respectively. Fruit yield was similar in both systems, ranging from 47.1 for conventional to 44.1 kg tree⁻¹ for organic farming, averaging 13.2 and 12.3 t·ha⁻¹, respectively. No differences between these systems were observed in terms of leaf nutrient status, with variations in the N, P, and K contents during the different phenological stages. The N, P, and K lessen during flowering and fruit growth; the highest levels of these nutrients were fixed at harvest. These patterns were the opposite in Ca and Mg, ascribable to the antagonism between K and both Ca and Mg. Thus, these findings highlight the need to establish the optimal use of irrigation water with respect to crop requirements, thereby encouraging sustainable subtropical farming in terraces. Full article

Fleshy fruits are characterized by having a developmentally and genetically controlled, highly intricate ripening process, leading to dramatic modifications in fruit size, texture, color, flavor, and aroma. Climacteric fruits such as tomato, pear, banana, and melon show a ripening-associated increase in respiration and ethylene production and these processes are well-documented. In contrast, the hormonal mechanism of fruit development and ripening in non-climacteric fruit, such as strawberry, grape, raspberry, and citrus, is not well characterized. However, recent studies have shown that non-climacteric fruit development and ripening, involves the coordinated action of different hormones, such as abscisic acid (ABA), auxin, gibberellins, ethylene, and others. In this review, we discuss and evaluate the recent research findings concerning the hormonal regulation of non-climacteric fruit development and ripening and their cross-talk by taking grape, strawberry, and raspberry as reference fruit species. Full article

Climate change, including more volatile weather and longer growing seasons, is causing stress on grapevines (Vitis spp.). A change in harvest timing of wine grapes can have significant consequences. Thus, two methods (crop forcing and complete removal of green tissue) were employed to simulate abiotic vine injury. The harvest of bunch grapes in Mississippi occurs during July, a very hot month. ‘Miss Blanc’ and ‘Villard Blanc’ had four different crop forcing treatments imposed to determine yield amount and harvest timing. All treatments reduced yield. Harvest was delayed by 50 days, a potentially positive shift that was not enough to escape high temperatures. ‘Villard Blanc’ had no flower or fruit development after crop forcing treatments in May and June. ‘Miss Blanc’ yields were also significantly reduced by these treatments. Removal of green tissue to simulate injury from weather events such as frost, freeze, wind, or hail in both Mississippi and Oklahoma revealed that lost growth could reduce yields from 19% to 81%, which could influence grape grower management decisions. Full article

Urban agriculture, due to its location, can play a key role in recycling urban waste streams, promoting nutrient recycling, and increasing sustainability of food systems. This research investigated the integration of brewery wastewater treatment through anaerobic digestion with substrate-based soilless agriculture. An experiment was conducted to study the performance of three different crops (mustard greens (Brassica juncea), basil (Ocimum basilicum), and lettuce (Lactuca sativa) grown with digested and raw brewery wastewater as fertilizer treatments. Mustard greens and lettuce grown in digested wastewater produced similar yields as the inorganic fertilizer control treatment, while basil had slightly lower yields. In all cases, crops in the digested wastewater treatments produced higher yields than raw wastewater or the no fertilizer control, indicating that nutrients in the brewery wastewater can be recovered for food production and diverted from typical urban waste treatment facilities. Full article

In this study, we evaluated crop productivity and physiology during the hydroponic cultivation of medium-sized and cherry tomato crops, using two experimental greenhouses. Of the greenhouses, one used dye-sensitized solar cell (DSSC) technology for covering material, whilst the other, a conventional one (CONV), was covered using diffusion glass as a control. The effect of the colored lighting that resulted from the DSSC glass filtering on the physiological response of the crops was examined by measuring the plant transpiration rate and leaf chlorophyll content. Furthermore, we evaluated potential differences in the concentration of phytochemical compounds, such as ascorbic acid, lycopene, and quality characteristics. Tomato plants in the DSSC greenhouse presented lower early and total yields, as well as lower chlorophyll content, stomatal conductance, photosynthetic rate, and transpiration rate values, especially in the medium-sized fruits, as compared to the CONV greenhouse. The DSSC greenhouse showed significantly higher values of bioactive compounds for both the cherry and medium-sized tomato, with increases in the ascorbic acid, lycopene, β-carotene, and total carotenoids concentration, which ranged from 6% to 26%. Finally, for both the hybrids, the 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) tests showed circa 10% and 5% increase, respectively, in the DSSC greenhouse. Full article

Horticultural greenhouse production in circumpolar regions (>60° N latitude), but also at lower latitudes, is dependent on artificial assimilation lighting to improve plant performance and the profitability of ornamental crops, and to secure production of greenhouse vegetables and berries all year round. In order to reduce energy consumption and energy costs, alternative technologies for lighting have been introduced, including light-emitting diodes (LED). This technology is also well-established within urban farming, especially plant factories. Different light technologies influence biotic and abiotic conditions in the plant environment. This review focuses on the impact of light quality on plant–microbe interactions, especially non-phototrophic organisms. Bacterial and fungal pathogens, biocontrol agents, and the phyllobiome are considered. Relevant molecular mechanisms regulating light-quality-related processes in bacteria are described and knowledge gaps are discussed with reference to ecological theories. Full article

Breadfruit (Artocarpus altilis) is a tropical fruit tree primarily grown as a staple crop for food security in Oceania. Significant wind damage has driven an interest in developing its dwarf phenotype. The presence of any dwarf breadfruit variety remains unknown. Little is known regarding the growth of the species on rootstocks. Here, we examined the phenotype of breadfruit plants growing on marang (Artocarpus odoratissimus) rootstocks within 18 months after grafting; we identified a rootstock-induced dwarf trait in the species. This dwarf phenotype was characterized by shorter stems, reduced stem thickness and fewer branches, with 73% shorter internode length, 51% fewer and 40% smaller leaves compared to standard size breadfruit plants. The height of breadfruit plants on marang rootstocks was reduced by 49% in 9 months, and 59% in 18 months after grafting. The results suggest marang rootstocks can be applied to breadfruit breeding program for tree vigor control. Further biochemical characterization showed plants on marang rootstocks displayed leaves without change of total chlorophyll content, but with lower total soluble sugars, and stems with reduced activity of plasma membrane H⁺-ATPase, a well-known primary proton pump essential for nutrient transport. The significance of the two parameters in rootstock dwarfing is discussed. Full article

Aquaponic systems are becoming more prevalent and have led to accurate mass and energy balance models that allow nutrient utilization to be maximized and plant and fish systems to be coupled or complimentary. Such models still do not address the potential of using the plant side as both the primary nitrification system and as a sink for the nitrate being produced from the fish system. However, using the plants as the nitrification system for the fish waste requires a better understanding and quantification of the nitrification capacity of the plant system. A series of experiments were conducted using butterhead lettuce (Lactuca sativa, cv. Flandria) in deep water culture rafts. Plants were grown under two growing conditions and were evaluated based upon harvestable weight. Treatment 1 (H5) consisted of a standard hydroponic nutrient solution maintained at pH 5.8, while treatment 2 (A7) consisted of an aquaponic waste solution maintained at pH 7.0. The aquaponic conditions were created from a fish rearing system using koi (Cyprinus carpio) that was continuously recirculated between the designated plant tubs and the fish tank with an in-line bead filter to capture and mineralize fish solids. The total root surface area was not significantly different between treatments, but the ratio of root surface area to root fresh weight was different, suggesting that aquaponic roots are finer than hydroponic roots. Predictive equations were developed to correlate root surface area to shoot or root fresh weight, which can be used to design the nitrification component for a recirculating aquaculture system (RAS), as part of an integrated aquaponic system. Full article

Water is the most limiting resource in many semi-arid areas of Mediterranean countries. Among the strategies to improve water productivity, the implementation of deficit irrigation (DI) strategies and the introduction of drought-tolerant crops in irrigated areas (such as almond) are being widely studied. Recently, the use of biostimulants to enhance crop tolerance to drought under water-scarcity scenarios is increasing. This work examines the response of three almond cultivars (‘Guara’, ‘Marta’, and ‘Lauranne’) in terms of yield and associated physiological responses in the main phenological stages to biostimulants (HYT^® A and HYT^® B plus) applied to young trees subjected to different irrigation levels: (i) a full irrigation treatment (FI), irrigated at 100% of crop evapotranspiration (ET_C); and (ii) sustained-deficit irrigation (SDI₇₅), irrigated at 75% of ET_C. Significantly higher yields were obtained with HYT applications in 2 of 3 cultivars; these differences were most evident in the SDI₇₅ treatment. In particular, ‘Guara’ registered the most significant improvements in nut yield when the HYT product was applied (15–20% higher). With regard to crop physiological responses, higher values of leaf water potential and stomatal conductance were noted with the HYT application in some cultivars and phenological stages. These results indicated that the use of biostimulants can be a feasible strategy for almond cultivation, especially when SDI is used. Full article

The aim of this study was to evaluate the grafting compatibility of different varieties of tomato (Solanum lycopersicum L.) scions on potato (Solanum tuberosum L.) rootstocks to develop a ‘pomato’ plant. In this study three potato varieties; Diamant (P1), Cardinal (P2) and Asterix (P3), and two tomato varieties; Bangladesh Agricultural Research Institute (BARI) tomato-2 (T1) and BARI tomato-11 (T2) were used to make the grafted combinations T1P1, T1P2, T1P3, T2P1, T2P2 and T2P3, designated G1, G2, G3, G4, G5, and G6, respectively. Tomato seedlings aged 25 (S1) and 35 days (S2) were selected as scions. Graft compatibility was analyzed based on the growth and yield of the pomato plants. The results revealed that varieties and scion age had a significant effect on the pomato fruit and tuber yield. The initiation of flowering was not affected by the various graft combinations; however, plant height, leaf number, branch number, number of clusters per plant, number of fruit per cluster, number of fruit per plant, fruit length, fruit diameter, single fruit weight and total fruit yield per plant were higher in G5S1 among the combinations. On the other hand, the number of tubers per plant, single tuber weight, and tuber yield per plant were highest for a few combinations. Overall, it was concluded that Cardinal (P2) and Asterix (P3) potato were the most compatible for grafting with BARI tomato-11 (T2) at the scion age of 25 days (S1), based on vegetative growth and fruit and tuber yield of pomato plants. Full article

Salt tolerant ornamental plants can be irrigated with alternative water sources that are typically saline as a sustainable practice for urban landscaping, especially in arid and semi-arid regions. However, the salt tolerance of many ornamentals is not known. An eight-week greenhouse experiment was conducted to assess the relative salt tolerance of four perennial ornamentals, ‘Angelina’ (Sedum rupestre), ‘Autumn Joy’ (S. telephium), ‘Blue Spruce’ (S. reflexum), and ‘Blue Daze’ (Evolvulus glomeratus). The plants were grown in pots with potting mix substrate and irrigated with control or saline solutions. The electrical conductivities (EC) of the saline solutions were 5.0 and 10.0 mS/cm. Data collected included relative shoot, root, and total dry weight (DW), visual score, shoot tissue concentrations of Na⁺, Cl⁻, K⁺, and Ca²⁺, and the K⁺/Na⁺ ratio. There were significant differences in treatment and varieties for all response variables, and some interactions were also significant, indicating different responses to salinity for the four varieties. Shoot, root, and total DW decreased with increasing salinity for all varieties. Visual score was highest in Autumn Joy and Blue Spruce when treated with EC5 and EC10 and lowest in Angelina and Blue Daze, the latter of which showed symptoms of moderate foliar damage including leaf necrosis, or “burn”, due to salt stress. The concentrations of Na⁺ and Cl⁻ in the shoot tissue increased with increasing salinity while K⁺ and Ca²⁺ and the K⁺/Na⁺ ratio tended to decrease. Of the four varieties of herbaceous perennial ornamentals evaluated in this study, Autumn Joy and Blue Spruce were considered the most relatively salt tolerant while Angelina and Blue Daze were least tolerant. Full article

The aim of this research was to evaluate postharvest cherry tomato (Solanum lycopersicum (L.) Mill.) yield and fruit quality as affected by grafting and irrigation water quality in the desert region of Israel. Tomato plants (scion cv. Lorka) were grafted onto 3 commercial tomato rootstocks (Resistar, Beaufort and TRS2) and were irrigated with 2 water qualities: fresh water (electrical conductivity (EC)-1.6 dS m⁻¹) and salty water (EC-4.0 dS m⁻¹). Fresh water significantly increased fruit yield by an average of 17% and fruit size, regardless of plant grafting and rootstock, but there were no significant differences in fruit size between the water treatments. However, salty water, but not grafting, significantly improved several quality parameters of fruit stored for 12 d at 12 °C followed by 2 d at 20 °C in simulated sea transport of produce from Israel to Europe and marketing. Fruit harvested from plants irrigated with salty water showed higher sweetness, sourness and, especially, better general taste, and significantly reduced off-flavor, compared with those irrigated with fresh water. The combination of ‘Lorka’ on ‘Resistar’ rootstock and resulted in the best external, internal, and sensory quality parameters at the end of storability and marketing simulation, while the lowest-quality parameters were in fruit harvested from ‘Lorka’ on ‘Beaufort’ rootstock. Full article

Throughout this study, the objective was to determine the most effective carbohydrate (CHO) sources under different light-emitting diodes (LEDs), and the impact of chlorocholine chloride (CCC), for the in vitro regeneration of the protocom-like bodies (PLBs) in Phalaenopsis ‘Fmk02010’. We applied 15 LEDs combined with three CHO sources and five CCC concentrations in the study. Organogenesis of PLBs was very poor in maltose both for the number of PLBs and their fresh weight (FW) compared to media containing sucrose and trehalose. Sucrose was the best CHO source under the red-white (RW) LED for the in vitro organogenesis of PLBs (PLBs: 54.13; FW: 0.109 g), while trehalose was best under the blue-white (BW) LED (PLBs: 36.33, FW: 0.129 g). The red-blue-white (RBW)-trehalose combination generated a suitable number of PLBs (35.13) with the highest FW (0.167 g). CCC at 0.01, 0.1, and 1 mgL⁻¹CCC had no effect on PLB formation or FW, but 10 mg L⁻¹ reduced both. RW-sucrose, BW-trehalose, and RBW-trehalose were the best combinations for PLB organogenesis. The addition of low concentrations of CCC in the plant culture medium are unnecessary. Full article

Cycas micronesica K.D. Hill trees on the island of Yap were used to determine the influence of position along the leaf rachis on macro- and micro-nutrient concentrations and how leaf age affected the results. The outcomes revealed improvements to sampling protocols for future cycad leaf research. The concentration of every element except carbon and copper was influenced by leaflet position along the rachis. Most elements exhibited similar patterns for the oldest and youngest leaves on a tree, but the influence of position along the rachis for nitrogen, phosphorus, calcium, zinc, and boron was highly contrasting for old versus young leaves. The elements with the greatest variability along the rachis were potassium, phosphorus, manganese, and zinc, with the difference in basal and terminal leaflets as great as four-fold. Sampling leaflets at one position on a cycad leaf may generate inaccurate elemental concentration results for most essential nutrients other than carbon and copper. We have added position of sampled leaflets within leaves as a mandatory component of what is recorded and reported for future cycad leaf tissue analyses. Leaflets that span the full length of the rachis should be included in cycad leaf samples that are collected for tissue analysis. Full article