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Scientia horticulturae
International Society for Horticultural Science
Scientia horticulturae

International Society for Horticultural Science

0304-4238

Scientia horticulturae/Journal Scientia horticulturaeSCIISTP
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    The involvement of abscisic acid in hydrogen gas-enhanced drought resistance in tomato seedlings

    Wang, ChunleiYan, MeiYao, YandongMou, Kaiping...
    10页
    查看更多>>摘要:Hydrogen gas (H-2) regulates plant responses to abiotic and biotic stresses. Abscisic acid (ABA) might alleviate the adverse effects of drought stress. However, the mechanisms by which ABA and H-2 ameliorate plant drought stress are unclear. Here, tomato "Micro-Tom" seedlings were used to investigate the interaction between H-2 and ABA under drought conditions. The results showed that both hydrogen-rich water (HRW) and ABA increased plant height, stem diameter and root activity of tomato seedlings under drought stress, with optimal concentrations of 75% and 150 mu M, respectively. HRW or ABA treatment was able to enhance drought tolerance by increasing photosynthesis, antioxidant enzyme activity and gene expression of antioxidant enzymes under drought stress. Fluridone (FLU), a synthetic inhibitor of ABA, significantly diminished the positive effects of HRW on plant height, stem diameter and root activity under drought stress, suggesting that ABA might play a crucial role in H-2 enhanced drought resistance in tomato seedlings. The results revealed that the ABA content in the PEG + HRW treatment was 18% higher than that in the polyethylene glycol (PEG) treatment alone. Furthermore, we found that H-2 enhanced endogenous ABA content by increasing zeaxanthin epoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED) and abscisic aldehyde oxidase (AAO) activities and the expression of SlZEP, SlNCED, and SlAAO. PEG + HRW treatment increased ZEP and NCED activities, which were 13% and 40% higher than those of PEG treatment, respectively. Meanwhile, the transcription levels of SlSnRK2 and SlAREB were upregulated by HRW or ABA under drought stress, whereas this upregulation was reversed by FLU. Thus, our results demonstrate that H2 was able to enhance drought resistance by regulating ABA biosynthesis and the expression of ABA signal transduction genes in tomato seedlings.

    Metabolic responses to drought stress and rehydration in leaves and roots of three Citrus scion/rootstock combinations

    Sousa, Andressa Rodrigues de OliveiraSilva, Edson Mario de AndradeCosta, Marcio Gilberto CardosoSoares Filho, Walter dos Santos...
    13页
    查看更多>>摘要:Drought is one of the most destructive environmental challenges for agriculture, and citrus trees are cultivated in semiarid areas. The current study used physiological and untarget mass spectrometry analysis to assess the differential response to drought and rehydration in leaves and roots of three scion/rootstock combinations in which the same scion Valencia Orange was grafted onto three different rootstocks, namely, 'Rangpur Lime', 'Sunki Maravilha' and 'Sunki Tropical', known to have a different response to drought. The main question to be answer was whether the soil disease tolerant 'Sunki Tropical' could be used as alternative to the drought tolerant/disease susceptible rootstock 'Rangpur lime' to cultivate citrus in semiarid areas. Thirty-seven metabolites in leaves and forty-six in roots, mainly amino acids, as well as a few carbohydrates and organic acids were found differentially expressed after drought and/or rehydration in the three combinations. Overall, the results demonstrated that the three scion/rootstock combinations responded differently at metabolite levels to water changes. The few leaf metabolites found in the scion grafted on 'Rangpur Lime' and 'Sunki Maravilha' support the respective drought avoidance and tolerance strategy, already observed in those rootstocks.'Rangur Lime' and 'Sunki Tropical' shared at roots levels several common drought response mechanisms. Moreover, the high number of differential metabolites triggered in the scion by 'Sunki Tropical' seems to be useful for overcoming the drought effects without depleting the fruit quality. From our data, we argue that 'Sunki Tropical' is a drought tolerant genotypes that could be used as alternative to 'Ranpur Lime' to sustain citrus production in semiarid areas.

    Effects of low and high red to far-red light ratio on tomato plant morphology and performance of four arthropod herbivores

    Dicke, MarcelMeijer, DavyMeisenburg, Maravan Loon, Joop J. A....
    6页
    查看更多>>摘要:Changing the spectral composition of light has numerous advantages for the production and quality of horticultural crops. However, changing the light spectrum to stimulate growth can have negative consequences for plant responses to biotic stress. Especially changes in the ratio between red and far-red light (R:FR) have an important effect on plant-herbivore interactions. A low R:FR is indicative of shading and competition for light and induces strong growth responses which are known as shade avoidance responses, including stem elongation and leaf hyponasty. Exposure to low R:FR also inhibits plant defensive responses against biotic agents and increases the performance of pests and pathogens. In this study we tested whether an increase in R:FR, through the supplementation of red light LEDs can be used to reduce the performance of arthropod herbivores. Tomato plants (Solanum lycopersocum) were exposed to three different R:FR ratios; 0.5 (shading), 1.2 (sunlight) and 5.2 (artificial) and infested with either caterpillars (Manduca sexta), spider mites (Tetranychus urticae), aphids (Myzus persicae) or whiteflies (Trialeurodes vaporariorum). Plants exposed to a low R:FR showed clear stem elongation and leaf hyponasty consistent with the shade-avoidance responses, while plants exposed to high R:FR showed reduced stem length and reduced hyponasty. The performance of all four herbivore species was significantly increased after exposure to low R:FR, although the strength of this effect varied between phloem feeding and tissue feeding herbivores. Increasing the R:FR only reduced the performance of the caterpillars and did not significantly affect the other herbivore species. These results indicate that herbivore species with different feeding strategies respond differently to changes in light quality. These findings have implications for the use of LEDs in greenhouse horticulture.

    Thermo-gas dynamics affect the leaf canopy shape and moisture content of aquaponic lettuce in a modified partially diffused microclimatic chamber

    Cuello, JoelDuarte, BernardoConcepcion, Ronnie, IIDadios, Elmer...
    12页
    查看更多>>摘要:Precise and timely monitoring of leaf water content and growth is necessary for precision agriculture. In this study, the impact of temperature and gas concentration variations was synthesized with leaf canopy shape and moisture content of aquaponic lettuce in a customized partially diffused microclimatic chamber equipped with an RGB camera. Using the acquired thermo-gas sensor data during the light-dependent photosynthetic reaction and dark-period aerobic respiration, it was analyzed with the extracted spectro-morphological leaf canopy signatures. Applying spectro-morphological leaf canopy data as input to the recurrent neural network it was possible to sensitively predict full moisture content (FMT) and equivalent water thickness (EWT) with 92.34% and 85.96% accuracy, respectively. A decrease in red green blue vegetation index (RGBVI) and an increase in excess of green (ExG) optical vegetation stress index corresponds to an increase in FMT. According to our data, it was possible to observe that the water content balance during the third week after sowing, follows the same trend observed for the oxygen production increase during the light period. Additionally, it was also possible to observe that uneven leaf broadening (canopy shape index > 1), low EWT, high photosynthetic quotient (PQ), and photothermal unit (PTU), and minimal temperature and humidity stretch resulted in higher oxygen production rates. A growing degree day of 23.46 +/- 0.30 degrees C day is ideal for aquaponic lettuce. Plants with six (6) weeks exhibited the highest thermal sensitivity (Q1) of 0.205. Overall, the developed model and observations allow concluding that the combined temperature-O2-CO2 dynamics monitoring must be considered to achieve maximum production rates. Moreover, in the framework of the new approaches developed within precision agriculture schemes, the collected optical data allied to the recurrent neural network are suitable tools for this continuous monitoring in an automated way.

    Exogenous application of indole-3-acetic acid to ameliorate salt induced harmful effects on four eggplants (Solanum melongena L.) varieties

    Li, Zhong-HuShahzad, KhurramSiddiqi, Ejaz HussainAhmad, Shakeel...
    11页
    查看更多>>摘要:Salinity is one of the significant widespread environmental stress that can limit the growth and development of plants. An experiment was conducted to find how the indole-3-acetic acid (IAA) ameliorates the effect of salinity (NaCl) on biomass production, physiological, biochemical, and yield attributes Brinjal (Solanum melongena L.). Four eggplant varieties (Signath 666, Cluster King, Black Round, and Desi) were treated with two levels of treatment with salt (Control, 80 mM NaCl) and foliar-applied indole-3-acetic acid (IAA) (Control, 2 mM IAA). The experiment was designed based on three replications and an utterly random structure. Physiological, biochemical, vegetative, and yield attributes were measured during the experiment. The results revealed that salinity at 80 mM affected the physiological and biochemical parameters that inhibited growth rate and resulted in yield reduction of brinjal plants. The foliar application of IAA overcame this reduction. However, some biochemical attributes, e.g., leaf proline, leaf glycine betaine analysis, and antioxidant enzyme activities, increased under salt stress. Overall, our results demonstrated that the salt-induced harmful effect was overcome by the exogenously applied IAA and increased biomass production, physiological, biochemical, and yield attributes in brinjal varieties.

    Informative title: Development of lighting intensity approach for shoot proliferation in Phalaenopsis amabilis through combination with silver nanoparticles

    Farrokhzad, YusufBabaei, AlirezaYadollahi, AbbasKashkooli, Arman Beyraghdar...
    9页
    查看更多>>摘要:This experiment was designed to improve shoot proliferation by optimizing light intensity and reducing the potential effects of ethylene such as explant yellowing, unexpanded leaf and narrow shoots. For this purpose, shoot tips as explants were cultured in to the Murashige and Skoog medium with major salts at half-strength supplemented with silver nanoparticles concentrations (0, 5, 10, 20, 40 mu M AgNPs) which were then exposed to three different light intensities (40, 80, 160 mu mol m(-2) s(-1)) for a period of three months. Morphological (leaf number, dry and fresh weight of regenerants), biochemical and oxidant/antioxidant responses of regenerants were quantified. According to the results, low light intensity (40 mu mol m(-2) s(-1)) stimulated the shoot proliferation of Phalaenopsis and the effects of 5 mu M AgNPs on shoot number while showing the maximum fresh and dry weight. It was also observed that chlorophyll, carbohydrate and protein content, enzymatic activity (superoxide dismutase and catalase), H2O2 generation, medium browning and phenolics content improve with higher light intensities (80 and 100 mu molm(-2) s(-1)). Higher AgNP concentrations reduced shoot proliferation, dry weight, and soluble proteins. The most effective combinatorial treatment for the shoot proliferation stage of Phalaenopsis was determined to be 5 mu M AgNPs and 40 mu mol m(-2) s(-1).

    Early apple fruit development under photoselective nets

    Boini, AlexandraCasadio, NicoloBresilla, KushtrimPerulli, Giulio Demetrio...
    10页
    查看更多>>摘要:The objective of this 2-year study (2017, 2019) was to evaluate the influence of photoselective nets on apple fruit growth, focusing on the initial fruit growth stages of "Pink Lady". Trees were subjected to four photoselective nets (Blue, Red, White and Yellow) and a standard black one (serving as Control), resulting in 5 light environments (LE), all shading at 20%. From 20 to 90 DAFB, 32 fruit and extension shoots, for each LE, were measured for a total of 11 times during the season. For each LE, fruit gauges were also installed to monitor fruit daily growth parameters, from 50 to 90 DAFB. At harvest, all fruit from each light environment were weighed and quality parameters were measured on 40 fruit per treatment. For each year, correlations were made to test the influence of LEs on final fruit weight and quality, and the impact that extension shoot growth had on fruit growth. In both years, white and control nets led to the production of fruits with higher weight compared to the other treatments (blue, red and yellow nets). In 2019, LEs did not appear to influence the relationship between shoot and fruit growth, probably due to the higher crop load and the massive pruning carried out the previous year. The higher vegetative outburst in this year might have unbalanced resources towards the shoots, than towards the fruit. Results show how weather and orchard management heavily influenced the trees responses. Yet, the consistent findings of final fruit weight, for both years, indicate that different wavelengths influence fruit and shoot behavior, even at early phenological stages. Hence, growers searching for bigger fruit should refer to white and black nets. Further studies approaching this technology can help improve apple production management and knowledge of the use of photoselective nets.

    Effects of elevated CO2 and nitrogen supply on leaf gas exchange, plant water relations and nutrient uptake of tomato plants exposed to progressive soil drying

    Yang, XinLiu, JieHu, XiaotaoLiu, Fulai...
    12页
    查看更多>>摘要:The effects of nitrogen (N) supply on the response of leaf gas exchange, leaf water relations and plant nutrient uptake of tomato plants exposed to progressive soil drying under elevated CO2 (e[CO2], 800 ppm) were inves-tigated. Two tomato genotypes differing in their endogenous abscisic acid (ABA) level, i.e. Ailsa Craig and its ABA-deficient mutant (flacca) were grown in pots in greenhouse cells with either ambient CO2 (a[CO2], 400 ppm) or e[CO2]. Two N levels, i.e., N1, 0.5 g pot(-1) and N2, 1.0 g pot(-1) were used and the N fertilizer (NH4NO3) was applied with the irrigation water before transplanting. The results showed that e[CO2] and N-2 increased photosynthesis and water use efficiency (WUE) of tomato plants. N2 improved plant water relations by sensi-tizing the decline of transpiration rate during soil drying. The plant N acquisition and major ionic concentrations in xylem sap were lowered under e[CO2], such negative effect was compensated by increasing N supply. For WT, the ABA concentrations in leaf ([ABA]leaf) and xylem sap ([ABA]xylem) were increased with the decrease of the fraction of transpirable soil water, whereas, for flacca this was only observed in [ABA]leaf. Compared to WT, flacca had lower xylem sap ionic concentrations and WUE. Collectively, the responses of tomato plants to e[CO2] and N supply under progressive soil drying were genotypic-dependent, and endogenous ABA level could play an important role in modulating the responses.

    Intercropping Wolfberry with Gramineae plants improves productivity and soil quality

    Zhu, LizhenHe, JunTian, YingLi, Xiaoying...
    13页
    查看更多>>摘要:The intercropping of shrubs with Gramineae species has been used widely to increase productivity and sustainability in modern agriculture. However, there have been few studies of intercropping of Wolfberry shrubs (Lycium barbarum) and it is cultivated mostly by clean tillage. In this study, we measured land productivity, crop yield and quality, and soil properties when L. barbarum was intercropped with Gramineae plants compared to when grown in a monoculture with clean tillage. The results showed that Wolfberry/ Gramineae intercropping improved productivity and fruit quality as evidenced by a significant increase in the Land Equivalent Ratio (LER) and the content in the fruit of carotenoid, flavonoid, total sugar and ascorbic acid. The nutrient content and enzyme activity of rhizosphere soils were higher under intercropping. The physical properties of the soil also improved with increased soil moisture, available potassium, available phosphorus and total nitrogen. The effect of intercropping on bacterial diversity was greater than that on fungal diversity, especially alpha diversity as shown by the Shannon Index, although both groups were markedly altered by intercropping. Binding spatial ordination analysis demonstrated that potassium and nitrogen were the nutrients that most affected the bacterial community, and all soil enzymes corelated with bacterial community composition. Collectively, these results suggest that intercropping of L. barbarum with Gramineae plants alters the soil bacterial community composition which reflects changes in soil properties and enzyme activities. Our findings show how to improve Wolfberry productivity and they provide insights into the mechanisms underlying healthy, biodiverse soils in agroecosystems.

    The Macadamia bloom - What are the hydrological implications?

    Shabalala, MlungisiToucher, MicheleClulow, Alistair
    8页
    查看更多>>摘要:Growing macadamia nut trees continues to gain popularity due to the delicacy and nutritional value associated with the nuts. These evergreen trees are grown in areas where rainfall quantity and distribution is often inadequate to sustain optimum yields. As a result, irrigation is often required to meet demands and achieve maximum profits. However, there is little detail on the minimum volume of water required during different growth stages to obtain optimal yields. This paper reviews existing studies on the plant-water relations of macadamia nut trees from the perspective of understanding their impacts on water resources. Macadamia trees have been found to use an average 75 L tree-1 day-1 in Australia, while values range between 4 and 71 L tree-1 day-1 for trees grown in South Africa. Macadamia trees are characterised by strict stomatal control, enabling them to maintain a favourable water status for prolonged periods under water stressed conditions. However, stress during the premature nut drop and oil accumulation stages decreases yield and quality. On the other hand, imposing stress at floral initiation increases yield. Therefore, stress manipulation may be a useful management tool for improved water use efficiency in commercial orchards. This requires accurate measurements of the thresholds for the maximum stress and minimum water required at these critical stages. Yield response to irrigation has been difficult to determine with confidence. Due to the cyclical nature of macadamia yields, it has been recommended that a minimum of five years is required to establish a relationship between water use and yield. There has been a limited amount of work done on the impacts of macadamia production on water resources and financial constraints are likely to limit this in the future. However, based on the rapid development of commercial macadamia orchards, future water-related research needs to consider macadamia production beyond tree and orchard scales, viewing macadamia as part of a socioecological system where orchard water use may impact on the availability and quality of water for other users, including the environment.