Effects of rotted corn straw on soil environment, yield, and quality of cucumber.

Aiming at solving the problems of soil environment deterioration and the decline of both yield and quality caused by excessive application of chemical fertilizer, we investigated the effects of rotted corn straw on the soil environment of root zone, yield and quality of cucumber with 'Jinyou 35' cucumber as the experimental material. There were three treatments, namely, combined application of rotted corn straw and chemical fertilizer (T1, the total nitrogen fertilizer application were 450 kg N·hm-2, of which 9000 kg·hm-2 rotted corn straw was used as the subsoil fertilizer, and the rest was supplemented with chemical fertilizer), pure chemical fertilizer (T2, the total nitrogen fertilizer application was the same as T1) and no fertilization (control). The results showed that the content of soil organic matter in root zone soil in T1 treatment was much higher, but no difference between T2 treatment and the control, after two continuous plantings in one year. The concentrations of soil alkaline nitrogen, available phosphorus, available potassium of T1 and T2 in cucumber root zone were higher than that in the control. T1 treatment had lower bulk density, but markedly higher porosity and respiratory rate than T2 treatment and the control in root zone soil. The electric conductivity of T1 treatment was higher than that of the control, but significantly lower than T2 treatment. There was no significant difference in pH among the three treatments. The quantity of bacteria and actinomycetes in cucumber rhizosphere soil were the highest in T1, and the lowest in the control. However, the highest quantity of fungi was found in T2. The enzyme activities of rhizosphere soil in T1 treatment were markedly higher than those of the control, whereas those of T2 treatment were significantly lower or had no significant difference relative to the control. The cucumber root dry weight and root activity of T1 were significantly higher than that of the control. The yield of T1 treatment increased by 10.1%, and fruit quality improved obviously. The root activity of T2 treatment was also significantly higher than that in the control. There was no significant difference in root dry weight and yield between T2 treatment and the control. Furthermore, T2 treatment revealed a decrease in fruit quality relative to T1 treatment. These results suggested that the combined application of rotted corn straw and chemical fertilizer could improve soil environment, promote root growth, enhance root activity and improve yield and quality of cucumber in solar-greenhouse, which could be popularized and applied in protected cucumber production.

Comparative transcriptome analysis of grafting to improve chilling tolerance of cucumber.

Grafting with pumpkin as rootstock could improve chilling tolerance of cucumber; however, the underlying mechanism of grafting-induced chilling tolerance remains unclear. Here, we analyzed the difference of physiological and transcriptional level between own-rooted (Cs/Cs) and hetero-grafted (Cs/Cm) cucumber seedlings under chilling stress. The results showed that grafting with pumpkin significantly alleviated the chilling injury as evidenced by slightly symptoms, lower contents of electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2-) and higher relative water content in Cs/Cm seedlings compared with Cs/Cs seedlings under chilling stress. RNA-seq data showed that grafting induced more DGEs at 8 °C/5 °C compared with 25 °C/18 °C. In accordance with the increase of the activities of antioxidant enzymes (SOD, POD, CAT, APX), grafting upregulated the expression of the regulated redox-related genes such as GST, SOD, and APX. Moreover, grafting increased the expression of genes participated in central carbon metabolism to promote the conversion and decomposition of sugar, which provided more energy for the growth of Cs/Cm seedlings under chilling stress. In addition, grafting regulated the genes involved in the intracellular signal transduction pathways such as calcium signal (CAML, CML, and CDPK) and inositol phospholipid signal (PLC), as well as changed the gene expression of plant hormone signal transduction pathways (ARF, GAI, ABF, and PYR/PYL). These results provide a physiological and transcriptional basis for the molecular mechanism of grafting-induced chilling tolerance of cucumber seedlings.

[Alleviating effect of exogenous melatonin and calcium on the peroxidation damages of cucumber under high temperature stress]. / å¤–æºè¤ªé»‘ç´ ä¸Žé’™ç¦»å­äº’ä½œå¯¹é«˜æ¸©èƒè¿«ä¸‹é»„ç“œå¹¼è‹—è¿‡æ°§åŒ–ä¼¤å®³çš„ç¼“è§£æ•ˆåº”.

To explore whether there is an interaction between melatonin (MT) and calcium (Ca2+) in regulating heat tolerance of plants, we analyzed the response of endogenous MT and Ca2+ to heat stress, and examined the effect of MT and Ca2+ on the reactive oxygen (ROS) accumulation, antioxidant system, and transcripts of heat shock factor (HSF) and heat shock proteins (HSPs) of cucumber seedlings under high temperature stress. Seedlings were foliar sprayed with 100 µmol·L-1 MT, 10 mmol·L-1 CaCl2, 3 mmol·L-1 ethylene glycol tetraacetic acid (EGTA, Ca2+ chelating agent) +100 µmol·L-1 MT, 0.05 mmol·L-1 chlorpromazine (calmodulin antagonist, CPZ) +100 µmol·L-1 MT, 100 µmol·L-1 p-chlorophenylalanine (p-CPA, inhibitor of MT) +10 mmol·L-1 CaCl2 or deionized water (H2O), respectively. The results showed that both endogenous MT and Ca2+ in cucumber seedlings were induced by high temperature stress. The seedlings treated with exogenous MT showed significant increases in the mRNA expression of calmodulin (CaM), calcium-dependent protein kinase (CDPK5), calcineurin B-like protein (CBL3) and CBL interacting protein kinase (CIPK2) compared with the control at normal temperature. The mRNA levels of tryptophane decarboxylase (TDC), 5-hydroxytryptamine-N-acetyltransferase (SNAT) and N-acetyl-5-hydroxytryptamine methyltransferase (ASMT), key genes of MT biosynthesis and endogenous MT content were also induced by Ca2+ in cucumber seedlings. Exogenous MT and CaCl2 alleviated the heat-induced oxidative damage through increasing antioxidant ability, reducing the accumulation of reactive oxygen species (ROS), and upregulating the mRNA abundances of HSF7, HSP70.1 and HSP70.11, as evidenced by mild thermal damage symptoms, lower heat injury index and electrolyte leakage under heat stress. The positive effect of MT-induced antioxidant capacity and mRNA expression of HSPs was removed by adding EGTA and CPZ in stressed seedlings. Similarly, the mitigating role of Ca2+ in the peroxidation damage to high temperature stress was reversed by p-CPA. These results suggested that both MT and Ca2+ could induce heat tolerance of cucumber seedlings, which had crosstalk in the process of heat stress signal transduction.

[Effects of fulvic acid on photosynthetic characteristics, yield and quality of cucumber under drought stress]. / é»„è é ¸å¯¹å¹²æ—±èƒè¿«ä¸‹é»„ç“œå ‰åˆç‰¹æ€§åŠäº§é‡å’Œå“è´¨çš„å½±å“.

Fulvic acid (FA) participates in the regulation of drought stress tolerance in plants, but the underlying mechanisms remain unclear. We carried out an experiment with cucumber cultivar 'Jinyou 35' as the test material and the polyethylene glycol (PEG-6000) being used to simulate drought stress. The concentration effect of FA on drought alleviation of cucumber as well as the effect of FA on photosynthetic enzymes activities, chloroplast ultrastructure, fluorescence parameters, water use efficiency, yield and quality of cucumber plants were studied through spraying FA with different concentrations (0, 100, 300, 500, 700 and 900 mg·L-1). The results showed that FA with different concentrations significantly promoted the relative water content and leaf area and decreased drought injure index as well as the electrolyte leakage and malondialdehyde (MDA) content, compared with the control (0 mg·L-1) under drought stress. The mitigative effect of FA increased first and then decreased with the increases of FA concentration, with 700 mg·L-1 FA showing the best effect. FA significantly enhanced the chlorophyll content, Rubiasco and Rubisco activase (RCA) activities and gene expression, net photosynthesis (Pn), maximal photochemical efficiency of PSⅡin darkness, actual photochemical efficiency, absorbed light energy per unit area, captured light energy per unit area, quantum yield of electron transport and PSⅠ activity, decreased the increase of K point and maintained chloroplast ultrastructure. The experiment in solar-greenhouse showed that FA obviously increased water use efficiency, promoted dry matter accumulation as well as the contents of Vc, soluble sugar, soluble protein and free amino acid, and decreased tannin content. Our results suggested that FA could improve the yield and quality of cucumber in solar greenhouse under drought stress.

Salicylic Acid Is Involved in Rootstock-Scion Communication in Improving the Chilling Tolerance of Grafted Cucumber.

Salicylic acid (SA) has been proven to be a multifunctional signaling molecule that participates in the response of plants to abiotic stresses. In this study, we used cold-sensitive cucumber and cold-tolerant pumpkin as experimental materials to examine the roles of SA in root-shoot communication responses to aerial or/and root-zone chilling stress in own-root and hetero-root grafted cucumber and pumpkin plants. The results showed that pumpkin (Cm) rootstock enhanced the chilling tolerance of grafted cucumber, as evidenced by the observed lower levels of electrolyte leakage (EL), malondialdehyde (MDA), and higher photosynthetic rate (Pn) and gene expression of Rubisco activase (RCA). However, cucumber (Cs) rootstock decreased the chilling tolerance of grafted pumpkins. Cs/Cm plants showed an increase in the mRNA expression of C-repeat-binding factor (CBF1), an inducer of CBF expression (ICE1), and cold-responsive (COR47) genes and CBF1 protein levels in leaves under 5/25 and 5/5°C stresses, or in roots under 25/5 and 5/5°C stresses, respectively, compared with the Cs/Cs. Chilling stress increased the endogenous SA content and the activity of phenylalanine ammonia-lyase (PAL), and the increase in SA content and activity of PAL in Cs/Cm plants was much higher than in Cs/Cs plants. Transcription profiling analysis revealed the key genes of SA biosynthesis, PAL, ICS, and SABP2 were upregulated, while SAMT, the key gene of SA degradation, was downregulated in Cs/Cm leaves, compared with Cs/Cs leaves under chilling stress. The accumulation of SA in the Cs/Cm leaves was mainly attributed to an increase in SA biosynthesis in leaves and that in transport from roots under aerial and root-zone chilling stress, respectively. In addition, exogenous SA significantly upregulated the expression level of cold-responsive (COR) genes, enhanced actual photochemical efficiency (Φ PSII), maximum photochemical efficiency (F v/F m), and Pn, while decreased EL, MDA, and CI in grafted cucumber. These results suggest that SA is involved in rootstock-scion communication and grafting-induced chilling tolerance by upregulating the expression of COR genes in cucumber plants under chilling stress.

[Hydrogen sulfide acted as a downstream signal was involved in the regulation of salicylic acid on photosynthesis of cucumber seedlings under low temperature and low light intensity]. / H2S作为下游信号参与SAå¯¹ä½Žæ¸©å¼±å ‰ä¸‹é»„ç“œå¹¼è‹—å ‰åˆä½œç”¨çš„è°ƒæŽ§.

Both salicylic acid (SA) and hydrogen sulfide (H2S) play an important role in regulating plant growth and development and physiological metabolism under abiotic stresses. As signal molecules, the interaction between them in regulating cucumber photosynthesis under low temperature and low light is still unclear. Here, we examined the regulation and interaction of SA and H2S on photosynthesis in cucumber seedlings under low temperature (8 ℃/5 ℃, day/night) and low light (100 µmol·m-2·s-1). Seedlings were foliar-sprayed with SA, sodium sulfide (NaHS, H2S donor), and their scavenger or biosynthesis inhibitors, respectively. Seedlings treated with deionized water at suitable temperature and light condition were used as the control. The results showed that SA increased the L-/D-cysteine desulfhydrase (LCD, DCD) activities and relative mRNA expression, and consequently promoted the endogenous H2S production. However, NaHS did not affect the activities and gene expressions of phenylalnine ammonialyase and isochorismate and endogenous SA level. Compared with the H2O-treated seedlings under low temperature and low light, SA- and NaHS-treated seedlings showed an increase in the photosynthetic rate, stomatal conductance and transpiration rate, while a decrease in intercellular CO2 concentration. SA and NaHS increased the CO2 assimilation, which mainly attributed to the increases in the activities of the ribulose-1, 5-bisphosphate carboxylase, rubisco activase, sedoheptulose-1, 7-bisphosphatase and fructose-1, 6-bisphosphatase, as well as their mRNA expression. Meanwhile, SA and NaHS improved the actual photochemical efficiency and maximal photochemical efficiency of PSII, and therefore alleviated the damage in photosynthetic apparatus and negative effect on growth from low temperature and low light stress. The SA-induced higher photosynthesis and growth in stressed seedlings were suppressed by addition of H2S scavenger hypotaurine. However, the H2S-induced tolerance of photosynthetic apparatus to low temperature and low light was not affected by SA biosynthesis inhibitor paclobutrazol and 2-aminoindan-2-phosphonic acid. Our results suggested that H2S, as a downstream signal of SA, was involved in regulating photosynthesis in cucumber seedlings under low temperature and low light.

Hydrogen sulfide is required for salicylic acid-induced chilling tolerance of cucumber seedlings.

Salicylic acid (SA) and hydrogen sulfide (H2S) have been proved to be multifunctional signal molecules to participate in the response of plants to abiotic stresses. However, it is still unclear whether there is interaction between SA and H2S in response to chilling intensity of cucumber seedlings. Here, we found SA was sensitive to chilling intensity. Under normal condition, NaHS (H2S donor) or removing endogenous H2S with hypotaurine (HT, a specific scavenger of H2S) and DL-propargylglycine (PAG, a specific inhibitor of H2S) has no effect on endogenous SA level; however, SA induced endogenous H2S content and activated the activities and mRNA level of L-/D-cysteine desulfhydrase (L-/D-CD), and inhibiting endogenous SA with paclobutrazol (PAC) or 2-aminoindan-2-phosphonic acid (AIP) blocked this effect, implying H2S may play a role after SA signal. Further studies showed that both SA and NaHS notably alleviated chilling injury, which was evidenced by lower electrolyte leakage (EL), MDA content, and ROS accumulation, compared with H2O treatment. Of note, SA and H2S improved the activities and mRNA level of antioxidant enzymes (SOD, POD, CAT, APX, and GR) as well as the contents of AsA and GSH. Additionally, the chilling-response genes (ICE, CBF1, and COR) were obviously upregulated by exogenous SA and NaHS. However, the positive effect of SA on chilling tolerance was inhibited by HT, whereas PAC or AIP did not affect NaHS-induced chilling tolerance. Taken together, the data reveals that H2S acts as a downstream signal of SA-induced chilling tolerance of cucumber via modulating antioxidant system and chilling-response genes.

Auxin acts as a downstream signaling molecule involved in hydrogen sulfide-induced chilling tolerance in cucumber.

MAIN CONCLUSION: This report proves a cross talk between H2S and IAA in cold stress response, which has presented strong evidence that IAA acts as a downstream signal mediating the H2S-induced stress tolerance in cucumber seedlings. We evaluated changes in endogenous hydrogen sulfide (H2S) and indole-3-acetic acid (IAA) emission systems, and the interactive effect of exogenous H2S and IAA on chilling tolerance in cucumber seedlings. The results showed that chilling stress increased the activity and relative mRNA expression of L-/D-cysteine desulfhydrase (L-/D-CD), which in turn induced the accumulation of endogenous H2S. Similarly, the endogenous IAA system was triggered by chilling stress. We found that 1.0 mM sodium hydrosulfide (NaHS, an H2S donor) significantly enhanced the activity of flavin monooxygenase (FMO) and relative expression of FMO-like proteins (YUCCA2), which in turn elevated endogenous IAA levels in cucumber seedlings. However, IAA had little effects on activities of L-/D-CD and endogenous H2S levels. H2S-induced IAA production accompanied by increase in chilling tolerance, as shown by the decrease in stress-induced electrolyte leakage (EL) and reactive oxygen species (ROS) accumulation, and increase in gene expressions and enzyme activities of photosynthesis. 1-naphthylphthalamic acid (NPA, an IAA polar transport inhibitor) declined H2S-induced chilling tolerance and defense genes' expression. However, scavenging of H2S had a little effect on IAA-induced chilling tolerance. These results suggest that IAA acting as a downstream signaling molecule is involved in the H2S-induced chilling tolerance in cucumber seedlings.

[Effects of light quality on carbon-nitrogen metabolism, growth, and quality of Chinese chives]. / å ‰è´¨å¯¹éŸ­èœç¢³æ°®ä»£è°¢ã€ç”Ÿé•¿å’Œå“è´¨çš„å½±å“.

We examined the effect of white + red (WR), white + blue (WB), white + green (WG), white + purple (WP) on the carbon-nitrogen metabolism, growth and quality of Chinese chives, with ‘Pingjiu 2’ as the material and white light (W) as the control. The results showed that photosynthetic rate (Pn) in WR treatment was significantly higher than that in the control (CK) and that there was no difference among WB, WG, WP and CK. The activity of RuBPCase in all the four treatments was higher than that in CK. Compared with other treatments, WR showed the highest total sugar content, then WP, with WB and WG showing the lowest. Compared with CK, sucrose phosphate synthase (SPS) activity in WR was higher, and lower in the other three treatments, especially the lowest in WB. WB showed the highest activity of sucrose synthetase (SS) and amylase (AMS), WR displayed the lowest as well as the similar or lower in WG or WP compared with CK. These results implied that the increases of the proportion of red and purple light could improve carbon assimilation and transformation and thus accelerate sugar accumulation of Chinese chives. The content of total nitrogen, protein nitrogen, the activities of NR, GS and GOGAT of WB were the highest among all the treatments. The GDH activity of WB was the lowest and notably lower compared with CK. WR showed the lower contents of total nitrogen, protein nitrogen, the activities of NR and GS, and higher activities of GOGAT and GDH than those in CK, while the GDH activity of WR was the highest. WG showed lower total nitrogen, no-protein nitrogen content, and GDH activity, but higher protein nitrogen, NR and GOGAT activities than those in CK. Compared with the control, WP showed the similar results as WG, besides the higher GS activity, with most of these parameters in WP being better than in WG. These results indicated that blue, purple and green light could promote nitrogen metabolism, while red light might inhibit protein synthesis in Chinese chives. The growth of Chinese chives was much better under red and purple light, but worse under blue light, which led to thinner leaves and lower growth mass. Chinese chives of WP with the lowest crude fiber content showed the optimal comprehensive quality. Therefore, purple light exhibited the best effect on the growth of Chinese chives.

[Effects of light quality ratio on photosynthetic characteristics and quality of purple lettuce]. / ä¸åŒå ‰è´¨é æ¯”å¯¹ç´«å¶ç”Ÿèœå ‰åˆç‰¹æ€§å’Œå“è´¨çš„å½±å“.

To explore the effects of different light quality ratios on the growth and development of purple lettuce, we used LED intelligent light control console as light source to study the effects of adding different proportions of red and blue light (1:1, 2:1, 4:1 and 1:2) to the white light on photosynthetic characteristics and commercial quality of purple lettuce (Lactuca sativa L. cv 'Zhongshu Purple Lettuce'). The results showed that when the ratio of red to blue light was 4:1, the chlorophyll content, RuBP carboxylase activity, electron transport efficiency of photosynthesis, net photosynthetic rate and growth were all significantly higher than that in control and other treatments, whereas the nitrate content was the lowest. When the ratio of red to blue light was 1:2, the contents of soluble protein, vitamin C, secondary metabolites such as anthocyanins, flavonoids, total phenolic compounds, and the contents of antioxidant capacity were significantly higher than those in the control and other treatments. We concluded that adding appropriate ratios of red to blue light to the white light could increase photosynthesis and improve commercial quality of purple lettuce.

[Response and adaptation of photosynthesis of cucumber seedlings to high temperature stress]. / é»„ç“œå¹¼è‹—å ‰åˆä½œç”¨å¯¹é«˜æ¸©èƒè¿«çš„å“åº”ä¸Žé€‚åº”.

Cucumber seedlings (Cucumis sativus Jinyou 35) were used to study the effects of high temperature (HT: 42 ℃/32 ℃) and sub-high temperature (SHT: 35 ℃/25 ℃) on its photosynthesis and growth. The results showed that the growth of cucumber seedlings was dramatically inhibited by the high and sub-high temperature stresses. The photosynthetic rate (Pn) was gradually reduced, while intercellular CO2 concentration (Ci) was increased as heat stress lasted. Under heat stress, stomatal conductance (gs), transpiration rate (Tr), photorespiration rate (Pr) and dark respiration rate (Dr) showed a trend from rise to decline in cucumber seedlings, which implied that heat-induced decline of photosynthesis was mainly due to non-stomatal limitation. Maximal photochemical efficiency of PS2 in darkness (Fv/Fm), actual photochemical efficiency (χPS2), photochemical quenching (qP) and electron transport rate (ETR) were severely hampered, while initial fluorescence (Fo) and non-chemical quenching (NPQ) were increased as a result of high and sub-high temperature stresses. Under extended high temperature stress, the activities of RuBP carboxylase (RuBPCase) and Rubisco activase (RCA) as well as the mRNA abundance of Rubisco and RCA were in the trend of decrease, while they were reduced 3 days following the sub-high temperature treatment. The activities and mRNA expressions of sedoheptulose-1,7-bisphosphatase (SBPase) and fructose 1,6-bisphosphate aldolase (FBA) increased initially, but decreased afterwards under heat stress. Taken together, our data suggested that short-term sub-high temperature did not cause photoinhibition under optimal light conditions, however, high temperature led to severe damage to PS2 reaction center in cucumber seedlings. The photosynthetic enzymes were induced by high temperature stress and the induction was affected by temperature and stress duration.

[Effect of water-nitrogen coupling on photosynthesis and ultrastructure of cucumber leaves under CO2 enrichment]. / CO2åŠ å¯Œä¸‹æ°´æ°®è€¦åˆå¯¹é»„ç“œå¶ç‰‡å ‰åˆä½œç”¨å’Œè¶ å¾®ç»“æž„çš„å½±å“.

Using split plot and then-split plot design, effects of water-nitrogen coupling on photosynthesis and ultrastructure of cucumber (Cucumis sativus) (Jinyou No.35) under CO2 enrichment were investigated. The main plot had two CO2 concentrations: ambient CO2 concentration (400 µmol·mol-1, A) and doubled CO2 concentration (800±20 µmol·mol-1, E). The split plot had two treatments: no drought stress (95% of field capacity, W) and drought stress (75% of field capacity, D). The then-split plot contained low nitrogen treatment (450 kg·hm-2, N1) and high nitrogen treatment (900 kg·hm-2, N2). The results showed that under the condition of drought and high nitrogen, increasing CO2 enhanced the cucumber plant height, and no matter what kinds of water treatment, CO2 enrichment increased the leaf area significantly under high nitrogen. Under the condition of normal irrigation, the photosynthetic rate, stomatal conductance and transpiration rate of high nitrogen treatment were higher than low nitrogen treatment, while it was under the drought condition. Elevated CO2 enhanced the water use efficiency of cucumber leaf which increased with increasing nitrogen application rate. Under drought stress, cucumber adaxial surface porosity density was increased, and the CO2 enrichment and high nitrogen significantly reduced the stomatal density. Increasing nitrogen application improved the number of chloroplast, and reduced that of starch grains. Drought stress decreased the number of chloroplast, but tended to promote the number of starch grains. Drought stress increased the chloroplast length and width, and the size of the starch grains, while high nitrogen reduced the length and width of the chloroplast and starch grains. CO2 enrichment and high nitrogen increased grana thickness and layers (except ADN2), and the slice layer of EDN2 was significantly higher than that of ADN2. In conclusion, CO2 enrichment and suitable water and nitrogen could promote the development of chloroplast thylakoid membrane system, significantly increase the thickness of grana and the number of grana lamella, and effectively improve the chloroplast structure of cucumber, which would benefit the photosynthesis of cucumber plants and ability to utilize CO2 and water and nitrogen.

Ultraviolet-B Radiation (UV-B) Relieves Chilling-Light-Induced PSI Photoinhibition And Accelerates The Recovery Of CO2 Assimilation In Cucumber (Cucumis sativus L.) Leaves.

Ultraviolet-B radiation (UV-B) is generally considered to negatively impact the photosynthetic apparatus and plant growth. UV-B damages PSII but does not directly influence PSI. However, PSI and PSII successively drive photosynthetic electron transfer, therefore, the interaction between these systems is unavoidable. So we speculated that UV-B could indirectly affect PSI under chilling-light conditions. To test this hypothesis, the cucumber leaves were illuminated by UV-B prior or during the chilling-light treatment, and the leaves were then transferred to 25 °C and low-light conditions for recovery. The results showed that UV-B decreased the electron transfer to PSI by inactivating the oxygen-evolving complex (OEC), thereby protecting PSI from chilling-light-induced photoinhibition. This effect advantages the recoveries of PSI and CO2 assimilation after chilling-light stress, therefore should minimize the yield loss caused by chilling-light stress. Because sunlight consists of both UV-B and visible light, we suggest that UV-B-induced OEC inactivation is critical for chilling-light-induced PSI photoinhibition in field. Moreover, additional UV-B irradiation is an effective strategy to relieve PSI photoinhibition and yield loss in protected cultivation during winter. This study also demonstrates that minimizing the photoinhibition of PSI rather than that of PSII is essential for the chilling-light tolerance of the plant photosynthetic apparatus.

[Effect of grafting on rhizosphere soil environment and its relationship with disease resistance and yield of pepper.] / å«æŽ¥å¯¹è¾£æ¤’æ ¹é™ åœŸå£¤çŽ¯å¢ƒçš„å½±å“åŠå ¶ä¸ŽæŠ—ç— æ€§å’Œäº§é‡çš„å ³ç³».

We investigated the effect of grafting on the root rhizosphere soil microorganisms, physical properties, nutrient content, soil-borne disease and yield of pepper, using 'Weishi' (WS) and 'Buyeding' (BYD) as rootstocks, the cultivar pepper 'Xinfeng 2' (XF) as scion, and the own-root (XF/XF) pepper as the control. The results indicated that XF/WS and XF/BYD significantly increased the populations of fungi and actinomycetes and the percentage of actinomycetes. 60 days after transplanting, the activities of catalase (CAT) and peroxidase (POD) were much higher in root rhizosphere soil of grafted pepper. 90 days after transplanting, the activities of phosphatase, invertase, urease, and nitrate reductase (NR) were much higher in root rhizosphere soil of XF/WS. In addition, The XF/WS and XF/BYD also highly increased hydrocarbon compounds in soil extraction, slightly increased electric conductivity (EC) but lowered nitrogen, phosphorus and potassium contents in root rhizosphere soil. Higher pH in root rhizosphere soil was found in XF/WS but not in XF/BYD. These data indicated that grafting could optimize the rhizosphere soil environment of pepper and enhance the resistance of soil-borne diseases. The yields of XF/WS and XF/BYD were increased by 40.8% and 28.7%, respectively.

[Effects of light quality on growth, secondary metabolites, and oxidative stress tolerance of Gynura bicolor.] / å ‰è´¨å¯¹ç´«èƒŒå¤©è‘µç”Ÿé•¿ã€æ¬¡ç”Ÿä»£è°¢å’ŒæŠ—æ°§åŒ–èƒè¿«çš„å½±å“.

The effects of white light, red light, blue light, yellow light, red+blue light and red+blue+yellow light on the growth and quality of Gynura bicolor were investigated under the same light intensity (350±5 µmol·m-2·s-1) by using light-emitting-diodes (LEDs) which could accurately regulate light quality and light intensity. The results indicated that compared with white light, red light could significantly promote the growth of G. bicolor and induce the accumulation of dry substance and soluble sugar content, but blue light inhibited the plant growth. The content of chlorophyll significantly decreased under the colored LEDs. Although the combination of red, blue and yellow light did not increase the dry substance accumulation, it resulted in significant elevation of total phenols, flavonoids and anthocyanins. The accumulation of these reduced substances could increase the tolerance to oxidative stress and the nutrient value in G. bicolor. This study provided a theoretical basis for G. bicolor diverse production regulated by light quality.

[Influence of over expression of CsRCA on photosynthesis of cucumber seedlings under high temperature stress.] / CsRCAè¶ è¡¨è¾¾å¯¹é«˜æ¸©èƒè¿«ä¸‹é»„ç“œå¹¼è‹—å ‰åˆä½œç”¨çš„å½±å“.

In the present work, transgenic cucumber seedlings over expressing CsRCA and wild-type cucumber seedlings '08-1'at three-leaf stage exposed to high temperature (40 ℃, PFD 600 µmol· m-2 · s-1) were used to study the regulatory mechanism of photosynthesis by CsRCA. The results showed that the mRNA abundance of rbcL and rbcS as well as the activities of ribulose bisphosphate carboxylic enzyme (Rubisco) and Rubisco activase (RCA) were significantly higher in CsRCA over-expressing cucumber seedlings than in wild type (WT). Following 2-h exposure to high temperature, a notable decrease was observed in photosynthetic rate (Pn), photochemical perfor-mance index based on the absorption of light energy (PIABS), activities of Rubisco and RCA as well as the relative expression of rbcL, rbcS and CsRCA in both wild-type cucumber seedlings and transgenic cucumber seedlings. It was found that high temperature stress led to higher Wk, a parameter of chlorophyll (Chl) a fluorescence OJIP curve. Furthermore, high temperature greatly reduced the efficiency of electron transfer along the electron transport chain beyond QA(ψ0) and the quantum yield for electron transport (φE0), indicating that PSII oxygen complexes (OEC) and electron transport chain downstream QA were inhibited by high temperature. However, the inhibition could be alleviated by over expressing CsRCA in cucumber seedlings. Taken together, our data suggested that over expressing CsRCA improves photosynthesis in cucumber seedlings under high temperature stress by enhancing activities of the Rubisco and RCA, and maintaining the number of active reaction centers.

[Effects of low magnesium on photosynthesis characteristics and antioxidant system in cucumber seedlings under low temperature].

The effects of low magnesium (30% Mg) stress on photosynthesis characteristics and antioxidant system in 'Jinyou 3' cucumber ( Cucumis sativa) seedlings under low temperature (day/ night temperature was 12 °C/8 °C) were investigated, with Hoagland nutrient solution treatment as the control. The results showed that the 30% Mg treatment showed a significantly lower Mg content in leaves, compared with the control. However, no marked difference in roots between the 30% Mg treatment and the control was found. Low temperature significantly decreased the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (g(s)), and carboxylation efficiency (CE), while increased the intercelluar CO2 concentration (Ci). The 30% Mg treatment showed significantly lower chlorophyll content, Pn, g(s) and CE, compared with the control. No marked change was found in Ci between the 30% Mg treatment and the control. Low magnesium stress resulted in a more serious damage in chloroplast membrane under low temperature, and showed lower chloroplasts, grains and lamellas, while more and larger starch grains in cucumber seedlings. Low magnesium stress also led to an increase in MDA content, while a decrease in activities of superoxide dismutase (SOD) , peroxidase (POD) , catalase ( CAT) , ascorbate peroxidase (APX) and glutathione reductase (GR). These data suggested that magnesium deficiency caused by its hindered transportation under low temperature was the main reason for the chlorosis of cucumber leaves. The decrease in Pn was mainly caused by the non-stomatal limitation. Low magnesium stress increased the influence of low temperature on Pn, and the resulting decline in Pn was caused by the stomatal limitation.

Water Status Related Root-to-Shoot Communication Regulates the Chilling Tolerance of Shoot in Cucumber (Cucumis sativus L.) Plants.

Although root-to-shoot communication has been intensively investigated in plants under drought, few studies have examined root-to-shoot communication under chilling. Here we explored whether root-to-shoot communication contributes to the chilling-light tolerance of cucumber shoots and clarified the key signal involves in this communication. After leaf discs chilling-light treatment, the photoinhibitions of Photosystem I (PSI) and Photosystem II (PSII) were similar in leaf discs of two cucumber varieties (JY-3 and JC-4). When the whole plants, including roots, were chilled under light, the photosynthetic performances in JC-4 leaves decreased more seriously than that in JY-3 leaves. However, when the water status of leaves was maintained by warming roots or floating the attached leaves on water, the PSII activity and amount of PSI in the leaves of the two varieties were similar after chilling-light treatment. In addition, the differences of PSII activities and amount of PSI between the two varieties under whole plant chilling-light treatment were independent of ABA pretreatment. Above results indicate that (1) the better water status in leaves under chilling contributes to the higher chilling tolerance of JY-3; (2) the water status, rather than an ABA signal, dominates root-to-shoot communication under chilling and the chilling tolerance of cucumber shoot.

[Responses of non-structural carbohydrate metabolism of cucumber seedlings to drought stress and doubled CO2 concentration].

The effects of doubled CO2 concentration on non-structural carbohydrate metabolism of cucumber (Cucumis sativus L. cv. 'Jinyou No.1') seedlings under drought stress were investigated. Split plot design was deployed, with two levels of CO2 concentrations (ambient CO2 concentration, 380 µmol . mol-1, and doubled CO2 concentration, 760±20 µmol . mol-1) in the main plots, and three levels of water treatments (control, moderate drought stress, and severe drought stress) simulated by PEG 6000 in the split-plots. The results showed that non-structural carbohydrates of cucumber leaves, including glucose, fructose, sucrose, and stachyose, increased with the doubling of CO2 concentration, which resulted in the decreased osmotic potential, improving the drought stress in cucumber seedlings. During the drought stress, sucrose synthase, soluble acid invertase and al- kaline invertase started with an increase, and followed with a decline in the leaves. In the root system, however, soluble acid invertase and alkaline invertase increased gradually throughout the whole process, whereas sucrose phosphate synthase firstly increased and then decreased. The treatment of doubled CO2 enhanced the activity of sucrose synthase, but decreased the activity of sucrose phosphate synthase. The synergistic action of the two enzymes and invertase accelerated the decomposition of sucrose and inhibited the synthesis of sucrose, leading to the accumulation of hexose, which lowered the cellular osmotic potential and enhanced the water uptake capacity. In conclusion, doubled CO2 concentration could alleviate the adverse effects of drought stress and improve the drought tolerance of cucumber seedlings. Such mitigating effect on cucumber was more significant under severe drought stress.

[Distribution and accumulation characteristics of nutrients in solar greenhouse soil in Ji'nan, Shandong Province of East China].

Taking the solar greenhouses with different cultivating years and vegetables in Ji'nan as test objects, this paper studied the amounts and frequency distribution of soil nutrients and the relationships between cultivating years and soil nutrients accumulation characteristics, and analyzed the factors causing soil salinization and acidification by fitting soil nutrients contents with cultivating years and vegetables. In the greenhouses, the contents of soil alkali-hydrolysable nitrogen, available phosphorus, available potassium, organic matter, and electrical conductivity were significantly higher than those in the open field, with an increment of 135.3%, 475.2%, 290.1%, 97.7%, and 188.7%, respectively, but the soil pH value was 0.31 lower than that of open field. The frequency distribution of soil nutrients presented a normal curve. Differences were observed in the soil nutrients contents in the greenhouses with different cultivating vegetables. The soil alkali-hydrolysable nitrogen content and electrical conductivity were in the order of tomato > cucumber > sweet pepper, soil organic matter content and pH value were cucumber > sweet pepper > tomato, soil available phosphorus content was cucumber > tomato > sweet pepper, and soil available potassium content was tomato > cucumber > sweet pepper. There was a mild tendency of soil acidification in soil alkali-hydrolysable nitrogen and available potassium. The decrease of soil pH was closely related to the accumulation of alkali-hydrolysable nitrogen. The soil nutrients accumulation in the greenhouses had the similar patterns, i. e. , rapid accumulation in the first two cultivating years, slowed down in the third and fourth year, and kept stable later, demonstrating a dynamic balance on the whole. All the nutrients contents were positively accumulated, while soil pH presented negatively. In the greenhouses with different cultivating vegetables, there was a significant correlation between soil nutrients and cultivating years, which could be fitted by conic curve or cubic curve.