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    园艺-栽培生理/资源品质合辑Horticulture — Physiology · Biochemistry · Cultivation

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    Potassium deficiency inhibits steviol glycosides synthesis by limiting leaf sugar metabolism in stevia (Stevia rebaudiana Bertoni) plants
    SUN Yu-ming, HUANG Xiao-lei, ZHANG Ting, YANG Yong-heng, CHENG Xiao-fang, XU Xiao-yang, YUAN Hai-yan
    2021, 20 (11): 2932-2943.   DOI: 10.1016/S2095-3119(20)63472-4
    Abstract86)      PDF in ScienceDirect      
    The steviol glycosides (SGs) in stevia (Stevia rebaudiana Bertoni) leaves are becoming increasingly valuable due to its high sweetness but low calorific value, which is driving the development of stevia commercial cultivation.  Optimizing fertilization management can effectively increase SGs productivity, but knowledge on the relationship between potassium (K) fertilization and SGs production is still lacking.  In this study, pot experiments were conducted in order to investigate the effect of K deficiency on SGs synthesis in stevia leaves, as well as the underlying mechanisms.  Our results showed that when compared with standard K fertilization, K deficiency treatment has no significant effect on the biomass of stevia plant grown in a given soil with high K contents.  However, K deficiency critically decreased leaf SGs contents as well as the expression of SGs synthesis-related genes.  The contents of different sugar components decreased and the activities of sugar metabolism-related enzymes were inhibited under the K deficiency condition.  Moreover, spraying sucrose on the leaves of stevia seedlings diminished the inhibitory effect caused by K deficiency.  Our results also revealed the significant positive correlations between sucrose, glucose and SGs contents.  Overall, our results suggest that K deficiency would suppress the synthesis of SGs in stevia leaves, and this effect may be mediated by the leaf sugar metabolism.  Our findings provide new insights into the improvement of SGs production potential. 
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    Optimization of rhizosphere cooling airflow for microclimate regulation and its effects on lettuce growth in plant factory
    LI Kun, FANG Hui, ZOU Zhi-rong, CHENG Rui-feng
    2021, 20 (10): 2680-2695.   DOI: 10.1016/S2095-3119(20)63382-2
    Abstract63)      PDF in ScienceDirect      
    In plant factories, the plant microclimate is affected by the control system, plant physiological activities and aerodynamic characteristics of leaves, which often leads to poor ventilation uniformity, suboptimal environmental conditions and inefficient air conditioning.  In this study, interlayer cool airflow (ILCA) was used to introduce room air into plants’ internal canopy through vent holes in cultivation boards and air layer between cultivation boards and nutrient solution surface (interlayer).  By using optimal operating parameters at a room temperature of 28°C, the ILCA system achieved similar cooling effects in the absence of a conventional air conditioning system and achieved an energy saving of 50.8% while bringing about positive microclimate change in the interlayer and nutrient solution.  This resulted in significantly reduced root growth by 41.7% without a negative influence on lettuce crop yield.  Future development in this precise microclimate control method is predicted to replace the conventional cooling (air conditioning) systems for crop production in plant factories.
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    The mitigation effects of exogenous dopamine on low nitrogen stress in Malus hupehensis
    LIU Xiao-min, GAO Teng-teng, ZHANG Zhi-jun, TAN ke-xin, JIN Yi-bo, ZHAO Yong-juan, MA Feng-wang, LI Chao
    2020, 19 (11): 2709-2724.   DOI: 10.1016/S2095-3119(20)63344-5
    Abstract71)      PDF in ScienceDirect      
    Dopamine plays numerous physiological roles in plants.  We explored its role in the regulation of growth, nutrient absorption, and response to nitrogen (N) deficiency in Malus hupehensis Rehd.  Under low N condition, plant growth slowed, and the net photosynthetic rates, chlorophyll contents, and maximal quantum yield of PSII (Fv/Fm) decreased significantly.  However, the application of 100 μmol L−1 exogenous dopamine significantly reduced the inhibition of low N stress on plant growth.  In addition to modifying root system architecture under low N supply, exogenous dopamine also changed the uptake, transport, and distribution of N, P, and K.  Furthermore, exogenous dopamine enhances the tolerance to low nitrogen stress by increasing the activity of enzymes (nitrate reductase, nitrite reductase, glutamic acid synthase and glutamine synthetase) involved in N metabolism.  We also found that exogenous dopamine promoted the expression of ethylene signaling genes (ERF1, ERF2, EIL1, ERS2, ETR1, and EIN4) under low N stress.  Therefore, we hypothesized that ethylene might be involved in dopamine response to low N stress in M. hupehensis.  Our results suggest that exogenous dopamine can mitigate low N stress by regulating the absorption of mineral nutrients, possibly through the regulation of the ethylene signaling pathway.
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    A new species of Malus in China, Malus shizongensis Liu sp. nov
    LIU Zhen-zhong, LI Zhong-xing, GAO Hua, BAO Cha-na
    2020, 19 (10): 2451-2457.   DOI: 10.1016/S2095-3119(20)63282-8
    Abstract95)      PDF in ScienceDirect      
    Based on morphological, molecular biological, and molecular systematic studies, we describe here a new species of Malus from Yunnan, China.  We compared the morphology of this new species, Malus shizongensis Liu sp. nov, with three Malus species, including M. hupehensis, M. baccata, and M. micromalus.  Although the appearance of M. shizongensis was similar to these three species, it differed in height, branch color, branch hair, and flower color.  To better identify the taxonomy of this new species, genome of M. shizongensis and that of seven Malus species, including M. prunifolia, M. sylvestris, M. sieversii, M. hupehensis, M. baccata, M. robusta, and M. micromalus were analyzed.  A phylogenetic tree based on genome analysis indicated that M. shizongensis was close to M. hupehensis.  Furthermore, M. shizongensis had its species-specific SNPs, and the number of species-specific SNPs was similar to that of three close species (M. hupehensis, M. baccata, and M. micromalus).  Based on the above information, we named this new species as M. shizongensis Liu sp. nov.
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    Efficiency of potassium-solubilizing Paenibacillus mucilaginosus for the growth of apple seedling
    CHEN Yan-hui, YANG Xiao-zhu, LI Zhuang, AN Xiu-hong, MA Ren-peng, LI Yan-qing, CHENG Cun-gang
    2020, 19 (10): 2458-2469.   DOI: 10.1016/S2095-3119(20)63303-2
    Abstract99)      PDF in ScienceDirect      
    Chemical potassium (K) fertilizer is commonly used in apple (Malus domestica L. Borkh) production but K is easily fixed by soil, resulting in reduced K fertilizer utilization and wasted resources.  K-solubilizing bacteria (KSB) can cost-effectively increase the soluble K content in rhizosphere soil.  Therefore, the objectives were to select high-efficiency KSB from apple orchards under various soil management models and evaluate their effects on apple seedling growth.  Maize (Zea mays L.) straw mulching (MSM) increased the total carbon (TC), total nitrogen (TN) and available potassium (AK) in the rhizosphere and improved fruit quality.  The number of KSB in the rhizosphere soil of MSM was 9.5×104 CFU g–1 soil, which was considerably higher than that in the other mulching models.  Fourteen KSB strains were isolated with relative K solubilizing ability ranging from 17 to 30%, and five strains increased the dry weight per apple seedling.  The most efficient strain was identified as Paenibacillus mucilaginosus through morphological observation and sequence analysis of 16S rDNA, named JGK.  After inoculation, the colonization of JGK in soil decreased from 4.0 to 1.5×109 CFU g–1 soil within 28 d.  The growth of the apple seedlings and the K accumulation in apple plants were promoted by irrigation with 50 mL JGK bacterial solution (1×109 CFU mL–1), but there was no significant increase in the AK content of rhizosphere soil.  High-performance liquid phase analysis (HPLC) data showed that the JGK metabolites contained phytohormones and organic acids.  Hence, the JGK strain promoted the growth of two-month-old apple seedlings by stimulating function of the produced phytohormones and enhanced K solubility by acidification for apple seedling uptake.  This study enriches the understanding of KSB and provides an effective means to increase the K utilization efficiency of apple production.
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    The effect of artificial solar spectrum on growth of cucumber and lettuce under controlled environment
    ZOU Jie, ZHOU Cheng-bo, XU Hong, CHENG Rui-feng, YANG Qi-chang, LI Tao
    2020, 19 (8): 2027-2034.   DOI: 10.1016/S2095-3119(20)63209-9
    Abstract68)      PDF in ScienceDirect      
    Light-emitting diodes (LEDs) have been widely applied in the controlled environment agriculture, which are characterized by relatively narrow-band spectra and energetical efficiency.  Most recently, the spectrum of Sunlike LEDs has been engineered and it closely resembles solar spectrum in the range of photosynthetic active radiation (PAR, 400–700 nm).  To investigate how plant growth responses to the spectrum of Sunlike LEDs, cucumber and lettuce plants were cultivated and their responses were compared with the conventional white LEDs as well as composite of red and blue LEDs (RB, R/B ratio was 9:1).  We observed that although Sunlike LEDs resulted in a longer stem in cucumber, dry weight and leaf area were similar as those under RB LEDs, and significantly higher than those under white LEDs.  Moreover, cucumber leaves grown under Sunlike and white LEDs showed higher photosynthetic capacity than those grown under RB LEDs.  For lettuce, plants grown under Sunlike LEDs showed larger leaf area and higher dry weight than the other two treatments.  However, the leaf photosynthetic capacity of lettuce grown under Sunlike LEDs was the lowest.  In this context, the spectrum induced plant functions are species-dependent.  Furthermore, the three types of LEDs show distinct light spectra and they are different in many aspects.  Therefore, it is difficult to attribute the different plant responses to certain specific light spectra.  We conclude that plants grown under Sunlike LEDs exhibit larger leaf area, which may be due to some specific spectrum distributions (such as more far-red radiation), and consequently are favorable for light interception and therefore result in greater production.
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    The effects of rootstocks on performances of three late-ripening navel orange varieties
    ZHU Shi-ping, HUANG Tao-jiang, YU Xin, HONG Qi-bin, XIANG Jin-song, ZENG An-zhong, GONG Gui-zhi, ZHAO Xiao-chun
    2020, 19 (7): 1802-1812.   DOI: 10.1016/S2095-3119(20)63212-9
    Abstract107)      PDF in ScienceDirect      
    Selection of rootstock is very important for citrus production.  Besides its major role on resistance, the rootstock also can affect fruit production and quality.  Currently, the main concerns on selection of rootstock for citrus production are compatibility and resistance, due to less information on the impacts of rootstock to the performance of scion varieties.  This study aims to provide information on performances of navel orange varieties on different rootstocks.  Three late-ripening navel orange varieties (Citrus sinensis var. Powell, Chislett and Banfield) grafted on seven rootstocks (Swingle citrumelo (C. paradisi×P. trifoliata), Carrizo citrange (C. sinensis×P. trifoliata), X639 (C. reticulata×P. trifoliata), MXT (C. sinensis×P. trifoliata), Hongju (C. reticulata), Ziyang Xiangcheng (C. junos) and trifoliate orange (P. trifoliata)) were used as plant materials for comprehensive comparison of the performances on tree growth, fruit yield and quality in 21 scion–stock combinations.  Investigation was carried out in these combinations in field nine years after planting.  Vigorous growth of all the three late-ripening navel orange varieties was observed on Carrizo citrange with the largest canopy volume at 33.34 m3 and the highest yield at 29.43 kg per tree, but a low yield efficiency at 2.87 kg m–3.  On the contrary, those on trifoliate orange had the smallest canopy volume at 10.79 m3 and the lowest fruit yield at 12.51 kg per tree, but the highest yield efficiency at 3.95 kg m–3. Rootstocks did not show significant effects on fruit size, fruit shape index, peel thickness and the edible rate of the fruits, but fruit quality was significantly affected by the rootstocks.  Fruits from the trees grafted on trifoliate orange presented the best quality with significantly higher total soluble solids (TSS) content than those on Ziyang Xiangcheng and Hongju, and also the highest ratio of TSS/titratable acidity (TA).  The TA content was observed from the fruits on X639 at 0.59 g 100 mL–1.  Vitamin C (Vc) content of fruits on Hongju was the highest at 49.25 mg 100 mL–1.  Growth vigor of the trees was positively correlated with fruit yield at an extremely significant level.  The canopy volume was negatively correlated with yield efficiency, but positively correlated with compatibility index.  Results of this study indicated that the rootstock has great impacts on the growth vigor of the tree, yield efficiency and quality of the fruit.  In order to achieve good quality and yield efficiency for navel orange production, less growth vigor rootstock such as trifoliate orange is highly recommended. 
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    Pearprocess: A new phenotypic tool  for stone cell trait evaluation in pear fruit
    XUE Yong-song, XU Shao-zhuo, XUE Cheng, WANG Run-ze, ZHANG Ming-yue, LI Jia-ming, ZHANG Shao-ling, WU Jun
    2020, 19 (6): 1625-1634.   DOI: 10.1016/S2095-3119(20)63193-8
    Abstract79)      PDF in ScienceDirect      
    The content of stone cells is an important factor for pear breeding as a high content indicates severely reduced fruit quality in terms of fruit taste.  Although the frozen-HCl method is currently a common method used to evaluate stone cell content in pears, it is limited in incomplete separation of stone cell and pulp and is time consuming and complicated.  Computer-aided research is a promising strategy in modern scientific research for phenotypic data collection and is increasingly used in studying crops.  Thus far, we lack a quantitative tool that can effectively determine stone cell content in pear fruit.  We developed a program, Pearprocess, based on an imaging protocol using computer vision and image processing algorithms applied to digital images.  Using photos of hand-cut sections of pear fruit stained with phloroglucin-HCl (Wiesner’s reagent), Pearprocess can extract and analyze image-based data to quantify the stone cell-related traits measured in this study: number, size, area and density of stone cell.  We quantified these traits for 395 pear accessions by Pearprocess and revealed large variation in different pear varieties and species.  The number of stone cells varied greatly from value of 138 to 2 866, the density of stone cells ranged from 0.0019 to 0.0632 cm2 cm–2, the distribution of stone cell area ranged from 0.06 to 2.02 cm2, and the stone cell size was between 2e-4 and 1e-3 cm2.  Moreover, trait data were correlated with fruit taste data.  We found that stone cell density is likely the most important factor affecting the taste of pear fruit.  In summary, Pearprocess is a new cost-effective web-application for semi-automated quantification of two-dimensional phenotypic traits from digital imagery using an easy imaging protocol.  This simpler, feasible and accurate method to evaluate stone cell traits of fruit is a promising new tool for use in evaluating future germplasms for crop breeding programs.
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    Response of axillary bud development in garlic (Allium sativum L.) to seed cloves soaked in gibberellic acid (GA3) solution
    LIU Hong-jiu, HUANG Cai-ping, TONG Pei-jiang, YANG Xue, CUI Ming-ming, CHENG Zhi-hui
    2020, 19 (4): 1044-1054.   DOI: 10.1016/S2095-3119(20)63156-2
    Abstract87)      PDF in ScienceDirect      
    Gibberellins (GAs) are important phytohormones that regulate many developmental processes in plants.  Clove, as the reproductive organ of garlic, dramatically affected garlic bulb development.  Considering the potential of gibberellins in plant development and our previous studies, we investigated the effect of soaking two types of seed cloves (seed clove-I: without root/shoot sprouting; seed clove-II: with root/shoot sprouting) in GA3 solution on axillary bud development and examined the effect of soaking seed cloves in GA3 solution on bulb development, phytohormone level and sugar content in this study.Results indicated seed clove types, soaking liquids and their interaction significantly affected the number of cloves per bulb and the rate of single-clove bulb.  Moreover, soaking seed cloves in 1 mmol L–1 GA3 solution for 24 h not only promoted axillary bud formation and secondary plant growth (equal to tillering or branching), but also slightly increased the number of cloves per bulb and changed bulb structure with a low yield and marketable quality.  On the 40th day after GA3 treatment (at axillary bud outgrowth stage), zeatin riboside (ZR) and soluble protein in stem were sharply increased with the increase of GA3, sucrose, fructose and soluble protein in leaf.  However, GA3, indole-3-acetic acid (IAA), soluble sugar and sucrose in stem (3.52 ng g–1 fresh weight (FW), 19.88 ng g–1 FW, 237.3 mg g–1 FW, and 8.24 mg g–1 FW, respectively) were significantly decreased on the 40th day after GA3 treatment, compared to the control of water treatment (5.56 ng g–1 FW, 32.96 ng g–1 FW, 263.6 mg g–1 FW, and 10.37 mg g–1 FW, respectively).  To our knowledge, these novel results indicate seed cloves soaked in GA3 solution promotes axillary bud formation and outgrowth that caused the changes in plant architecture and bulb structure.  Meanwhile, our findings suggest that the level of endogenous plant hormone (GA3, IAA and ZR) cooperates with the content of sugar (sucrose and fructose) in leaf and stem to regulate axillary bud outgrowth in garlic.
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    Physiological evaluation of nitrogen use efficiency of different apple cultivars under various nitrogen and water supply conditions
    WANG Qian, LIU Chang-hai, HUANG Dong, DONG Qing-long, LI Peng-min, Steve van NOCKER, MA Feng-wang
    2020, 19 (3): 709-720.   DOI: 10.1016/S2095-3119(19)62848-0
    Abstract100)      PDF in ScienceDirect      
    Nitrogen (N) deficiency is a common problem for apple (Malus×domestica) production in arid regions of China.  However, N utilization efficiency (NUE) of different apple cultivars grown under low N conditions in arid regions has not been evaluated. In this study, NUE was assessed for one-year-old seedlings of six apple cultivars, Golden Delicious, Qinguan, Jonagold, Honeycrisp, Fuji and Pink Lady, grafted onto Malus hupehensis Rehd. rootstocks.  Four treatments were used, including control water with control N (CWCN), limited water with control N (LWCN), control water with low N (CWLN) and limited water with low N (LWLN).  Our results showed that growth indices such as biomass, plant height and stem diameter, and photosynthetic rate of all cultivars decreased in the order CWCN>CWLN>LWCN>LWLN.  When subjected to LWLN treatment, Qinguan showed better growth and photosynthetic characters than other tested cultivars.  Additionally, Qinguan and Pink Lady had higher NUE, while Honeycrisp and Jonagold had lower NUE, based on the determination of biomass, photosynthetic parameters, chlorophyll content, the maximal photochemical efficiency of PSII (Fv/Fm), 15N and N contents.
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    Growth simulation and yield prediction for perennial jujube fruit tree by integrating age into the WOFOST model
    BAI Tie-cheng, WANG Tao, ZHANG Nan-nan, CHEN You-qi, Benoit MERCATORIS
    2020, 19 (3): 721-734.   DOI: 10.1016/S2095-3119(19)62753-X
    Abstract78)      PDF in ScienceDirect      
    Mathematical models have been widely employed for the simulation of growth dynamics of annual crops, thereby performing yield prediction, but not for fruit tree species such as jujube tree (Zizyphus jujuba).  The objectives of this study were to investigate the potential use of a modified WOFOST model for predicting jujube yield by introducing tree age as a key parameter.  The model was established using data collected from dedicated field experiments performed in 2016–2018.  Simulated growth dynamics of dry weights of leaves, stems, fruits, total biomass and leaf area index (LAI) agreed well with measured values, showing root mean square error (RMSE) values of 0.143, 0.333, 0.366, 0.624 t ha–1 and 0.19, and R2 values of 0.947, 0.976, 0.985, 0.986 and 0.95, respectively.  Simulated phenological development stages for emergence, anthesis and maturity were 2, 3 and 3 days earlier than the observed values, respectively.  In addition, in order to predict the yields of trees with different ages, the weight of new organs (initial buds and roots) in each growing season was introduced as the initial total dry weight (TDWI), which was calculated as averaged, fitted and optimized values of trees with the same age.  The results showed the evolution of the simulated LAI and yields profiled in response to the changes in TDWI.  The modelling performance was significantly improved when it considered TDWI integrated with tree age, showing good global (R2≥0.856, RMSE≤0.68 t ha–1) and local accuracies (mean R2≥0.43, RMSE≤0.70 t ha–1).  Furthermore, the optimized TDWI exhibited the highest precision, with globally validated R2 of 0.891 and RMSE of 0.591 t ha–1, and local mean R2 of 0.57 and RMSE of 0.66 t ha–1, respectively.  The proposed model was not only verified with the confidence to accurately predict yields of jujube, but it can also provide a fundamental strategy for simulating the growth of other fruit trees.
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    Allelochemical p-hydroxybenzoic acid inhibits root growth via regulating ROS accumulation in cucumber (Cucumis sativus L.)
    HUANG Cheng-zhen, XU Lei, Sun Jin-jing, ZHANG Zhong-hua, FU Mei-lan, TENG Hui-ying, YI Ke-ke
    2020, 19 (2): 518-527.   DOI: 10.1016/S2095-3119(19)62781-4
    Abstract61)      PDF in ScienceDirect      
    Allelopathy is prevalent in agricultural ecosystems and mediated by plant-derived secondary metabolites (allelochemicals).  Allelochemicals are released by donor plants and affect the root growth and development of receptor plants.  Allelopathy is responsible for the continuous cropping obstacles in cucumber (Cucumis sativus L.).  p-Hydroxybenzoic acid (pHBA), an autotoxin from root exudates of cucumber, has been proposed to be an important allelopathic chemical.  However, the molecular mechanism by which pHBA affect root growth and development in cucumber is unknown.  Here, we found that pHBA treatment suppressed root growth of cucumber by reducing the meristem activity and cell length.  This root growth defect is caused by reduced reactive oxygen species (ROS) accumulation in root tips.  After pHBA treatment, the expression levels of several ROS-scavenging-related genes were increased, including peroxidase (POD), catalase (CAT) and metallothionein (MT).  Moreover, exogenously application of salicylhydroxamate (SHAM), a peroxidase inhibitor, can partially restore the pHBA treatment induced root growth inhibition.  Furthermore, we found that there is natural variation for the inhibitory effect of pHBA on root growth.  We also showed that pHBA treatment could maintain higher level of ROS accumulated in the pHBA less sensitive cucumber than that in the pHBA-sensitive cucumber.  These results suggest that pHBA inhibits root growth by reducing root tip ROS level in cucumber.
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    Comparative transcriptome analysis of the effect of different heat shock periods on the unfertilized ovule in watermelon (Citrullus lanatus)
    ZHU Ying-chun, SUN De-xi, DENG Yun, AN Guo-lin, LI Wei-hua, SI Wen-jing, LIU Jun-pu, SUN Xiao-wu
    2020, 19 (2): 528-540.   DOI: 10.1016/S2095-3119(19)62777-2
    Abstract81)      PDF in ScienceDirect      

    In vitro gynogenesis is an important tool used in haploid or homozygous double-haploid plant breeding.  However, because of low repeatability, embryoid induction rate and quality, the molecular mechanisms remain poorly understood.  Heat shock treatment can promote the transformation of the gametophytic pathway into the sporophyte pathway, which induces the occurrence of haploid.  In this study, unfertilized ovaries were heat shocked for 0 h (A0) before flowering and for 0 h (A1), 4 h (A3), 8 h (A5), 12 h (A7), and 24 h (A8), respectively, at 37°C at the first day of the flowering stage.  The ovule enlargement rate was increased from 0% at 25°C to 96.8% at 37°C (24 h treatment).  Thus, we aimed to investigate the gene expression patterns in unfertilized ovules of watermelon after different periods of heat shock by using RNA-Seq technology.  The results showed that compared with A3, A5, A7, and A8, the biosynthesis of amino acid, glycine, serine and threonine metabolic pathways in A1 has changed significantly.  This indicated that heat shock treatment affected the synthesis and transformation of amino acids during ovule expansion.  The transcriptome data suggested gene expressions of ovule growth were significantly changed by heat-specific influences.  The results provide new information on the complex relationship between in vitro gynogenesis and temperature.  This provides a basis for further study of the mechanism of heat shock affecting the expansion of watermelon ovule. 

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    Selenium distribution and nitrate metabolism in hydroponic lettuce (Lactuca sativa L.): Effects of selenium forms and light spectra
    BIAN Zhong-hua, LEI Bo, CHENG Rui-feng, WANG Yu, LI Tao, YANG Qi-chang
    2020, 19 (1): 133-144.   DOI: 10.1016/S2095-3119(19)62775-9
    Abstract78)      PDF in ScienceDirect      
    A deficiency in selenium (Se) in the human diet is a worldwide problem.  The intake of Se-rich vegetables can be a safe way to combat Se deficiency for humans.  However, most leafy vegetables can accumulate a high content of nitrates, which poses a potential threat to human health.  Light is an important environmental factor that regulates the uptake and distribution of mineral elements and nitrogen metabolism in plants.  However, the effects of Se forms and light conditions, especially light spectra, on the uptake and translocation of Se and on nitrate reduction are poorly understood.  In this study, lettuce (Lactuca sativa L.) was treated with exogenous Se applied as selenate (10 mmol L–1) and selenite (0.5 mmol L–1) and grown under five different light spectra: fluorescent light (FL), monochromatic red LED light (R), monochromatic blue LED light (B), and mixed red and blue LED light with a red to blue light ratio at 4 (R/B=4), 8 (R/B=8), and 12 (R/B=12), respectively.  The effects of light spectra and Se forms on plant growth, photosynthetic performance, Se accumulation and nitrate reduction were investigated.  The results showed that the light spectra and Se forms had significant interactions for plant growth, foliar Se accumulation and nitrate reduction.  The Se concentration and nitrate content in the leaves were negatively correlated with the percentage of red light from the light sources.  Compared to Se applied as selenite, exogenous Se applied as selenate was more effective in reducing nitrate via promoting nitrate reductase and glutamate synthase activities.  The lowest nitrate content and highest plant biomass were observed under R/B=8 for both the selenate and selenite treatments.  The significant effect of the light spectra on the root concentration factor and translocation factor of Se resulted in marked variations in the Se concentrations in the roots and leaves.  Compared with FL, red and blue LED light led to significant decreases in the foliar Se concentration.  The results from this study suggest that the light spectra can contribute to Se distribution and accumulation to produce vegetables with better food quality. 
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