Helium, previously described as "biologically inert", displays great medicinal potential in a number of respiratory ailments via influencing redox signaling. However, whether or how this gas functions in plant biology is still elusive. Here, hydroponic and pot experiments showed that mimicking the responses achieved by nitric oxide (NO)-releasing compound, exogenous helium supply with helium-enriched solution or its fumigation significantly prevented NaCl-induced growth inhibition of alfalfa seedlings. Lower level of Na+/K+ ratio in both root and shoot parts caused by lower efflux of net K+ and higher efflux of net Na+, as well as higher abundances of ion transport genes (SOS1, SOS2, SOS3, NHX1, HKT1, and AKT1) were simultaneously observed. Consistently, reactive oxygen species (ROS) accumulation and oxidative injury were abolished by helium. These were further supported by stimulating antioxidant machinery and reprogramming gene expression related to antioxidant defence and related transcriptional factors (MYB4, WRKY33, ERF8, and ERF11) against salinity toxicity. Further experiments showed that helium supplementation strengthened endogenous NO production by up-regulating the expression of nitrate reductase (NR2) and its enzymatic activity, and NO-based S-nitrosylation was further influenced. Above responses were remarkably impaired by the removal of endogenous NO when its scavenger was added. Overall, these results revealed that helium control of salinity tolerance is partially mediated by a NO signaling cascade governing redox and ion homeostasis reestablishment, two important defense strategies against salinity stress.

Although hydrogen gas (H2)-treated soil improves crop biomass, this approach appears difficult for field application due to the flammability of H2 gas. In this report, we investigated whether and how H2 applied in hydrogen nanobubble water (HNW) improves the yield and quality of cherry tomato (Lycopersicon esculentum var. cerasiforme) with and without fertilizers. Two-year-long field trials showed that compared to corresponding controls, HNW without and with fertilizers improved the cherry tomato yield per plant by 39.7% and 26.5% in 2021 (Shanghai), respectively, and by 39.4% and 28.2% in 2023 (Nanjing), respectively. Compared to surface water (SW), HNW increased the soil available nitrogen (N), phosphorus (P), and potassium (K) consumption regardless of fertilizer application, which may be attributed to the increased NPK transport-related genes in roots (LeAMT2, LePT2, LePT5, and SlHKT1,1). Furthermore, HNW-irrigated cherry tomatoes displayed a higher sugar–acid ratio (8.6%) and lycopene content (22.3%) than SW-irrigated plants without fertilizers. Importantly, the beneficial effects of HNW without fertilizers on the yield per plant (9.1%), sugar–acid ratio (31.1%), and volatiles (20.0%) and lycopene contents (54.3%) were stronger than those achieved using fertilizers alone. In short, this study clearly indicated that HNW-supplied H2 not only exhibited a fertilization effect on enhancing the tomato yield, but also improved the fruit’s quality with a lower carbon footprint.

Hydrogen sulfide (H2S) plays prominent multifunctional roles in the mediation of various physiological processes and stress responses to plants. In this study, hydroponic experiments were carried out to explore the effects of NaHS pretreatment on the growth of wheat (Triticum aestivum L.) under 50 μM cadmium (Cd). Compared with Cd treatment alone, 50 μM NaHS pretreatment increased the plant height, soluble sugar content of shoots and roots, and dry weight of shoots and roots under Cd stress, while the Cd concentration of shoots and roots was significantly reduced by 18.1% and 25.9%, respectively. Meanwhile, NaHS pretreatment protected the photosynthetic apparatus by increasing the net photosynthetic rate and PSII electron transportation rate of wheat leaves under Cd stress. NaHS pretreatment significantly increased the soluble sugar content to maintain the osmotic pressure balance of the leaf cells. The gene expression results associated with photosynthetic carbon assimilation and sucrose synthesis in wheat leaves suggested that the NaHS pretreatment significantly up-regulated the expression of TaRBCL, TaRBCS, and TaPRK, while it down-regulated the expression of TaFBA, TaSuSy, TaSAInv, and TaA/NInv. In summary, NaHS pretreatment improved the resistance of wheat seedlings under Cd stress by increasing the rate of photosynthesis and regulating the expression of genes related to sugar metabolism.

[Objectives]The purpose of this study was to investigate the regulation and mechanism of hydrogen-rich water（HRW）on the growth and photosynthesis of strawberry（Fragaria×ananassa Duch.）. This would benefit agriculture by the application of HRW. [Methods]HRW was used to irrigate strawberries, and parameters such as leaf growth, photosynthetic gas exchange and photosynthetic efficiency were determined. Surface water irrigation was as the control. [Results]After the treatment, the leaf area of strawberries increased, the dry weight and fresh weight of leaves increased by 57.7% and 60.4%,respectively, and the relative growth rate and net assimilation rate increased by 50.0% and 59.9%,respectively, indicating that HRW had a significant effect in promoting strawberry growth. After HRW treatment, the chlorophyll a content increased by 14.4%,the chlorophyll b content did not change significantly, and the net photosynthetic rate of leaves increased by 22.3%,the contents of soluble sugar, glucose and sucrose in leaves significantly increased. After HRW treatment, the electron transport rate of PSⅡ increased but was not significant, while the significant decrease of quantum yield of photosystems Ⅱ nonregulatory energy dissipation Y（NO）indicated that the protection and regulation ability of the PSⅡ of strawberry leaves was improved. While the electron transport rate of PSⅠand effective photochemical quantum yield Y（I）significantly increased, suggesting that the cyclic electron flow of PSⅠwas improved. Further analysis showed that the transmembrane proton gradient（ΔpH）was significantly higher than that of the control, accounting for the main part of proton motive force, and the ATP content increased by 43.9% compared with the control, confirming the cyclic electron flow results. [Conclusions]Hydrogen-rich water can promote growth and photosynthesis of strawberry leaf by enhancing cyclic photosynthesis electron flow.

Although hydrogen gas (H2) treated soil improves crop biomass, this approach appears difficult for the field application due to the flammability of H2 gas. In this report, we investigated whether and how H2 applied in hydrogen nanobubble water (HNW) improves the yield and quality of cherry tomato (Lycopersicon esculentum var. cerasiforme) with/without fertilizers. Two-year field trials showed that compared to corresponding controls, HNW without/with fertilizers improved cherry tomato yield per plant by 39.7% and 26.5% in 2021 (Shanghai), and 39.4% and 28.2% in 2023 (Nanjing). Compared to surface water (SW), HNW increased soil available nitrogen (N), phosphorus (P), and potassium (K) consumption regardless of fertilizer application, which may be attributed to the increased NPK transport related genes in roots (LeAMT2, LePT2, LePT5, and SlHKT1,1). Also, HNW-irrigated cherry tomato displayed higher sugar-acid ratio (8.6%) and lycopene content (22.3%) than SW-irrigated plants without fertilizers. Importantly, the beneficial effects of HNW without fertilizers on yield per plant (9.1%), sugar-acid ratio (31.1%), volatiles (20.0%) and lycopene contents (54.3%) were stronger than those achieved by fertilizers alone. In short, this study clearly indicated that HNW-supplied H2 not only exhibited fertilization effect on enhancing tomato yield, but also improved fruit quality with a lower carbon footprint.

Cadmium (Cd)-contaminated soil has been receiving increasing attention worldwide due to the great harm it causes via food-chain enrichment through crops such as wheat. However, there is little research regarding the effects of mannose (MAN) on plants in response to Cd stress. Hence, hydroponic and potted soil experiments were conducted to investigate the mitigation effects of MAN on wheat under Cd stress and the possible mechanism. Compared with Cd treatment alone, foliar spraying of 160 μM MAN significantly reduced the Cd accumulation in shoots and increased the Cd retention in roots. The content of hemicellulose was increased by MAN treatment, and the proportion of Cd retained by hemicellulose in the cell wall of roots was increased. Furthermore, 160 μM MAN significantly reduced the water-extracted and ethanol-extracted Cd in roots, which are easily transported to shoots. In potted soil experiments using Cd-contaminated soil, MAN reduced the Cd content in wheat grain by 26.3%, compared with the control. These findings indicate that foliar spraying of 160 μM MAN resulted in less Cd being transported from roots to shoots by increasing the Cd retention in the cell wall and changing the Cd chemical forms in roots, which promoted wheat growth and reduced the Cd concentration in wheat grain.

[目的]本文旨在阐述喷施甘露糖缓解小麦镉(Cd)胁迫和抑制Cd转运的分子机制.[方法]测定小麦生长、生理、生化指标和分析根系蛋白组学差异,经过KEGG和GO注释方法分析差异蛋白所涉途径的相关信息,进一步用Real-time PCR验证差异表达蛋白.[结果]甘露糖处理15 d后,小麦根长和根干重分别增加54.8％和29.5％;地上部Cd总含量减少33.6％,而地下部增加58.1％.Cd转运系数减小47.7％,小麦Cd转运被抑制.叶片和根中谷胱甘肽(GSH)含量分别增加11.1％和42.8％,氧化型谷胱甘肽(GSSG)含量分别减少43.2％和49.3％.叶片和根活性氧分子的积累减少,表明小麦所受氧化胁迫减轻.甘露糖处理后,谷胱甘肽还原酶(GR)活性明显升高,过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性没有明显变化.处理后根中共有222个蛋白质发生显著变化,分别属于谷胱甘肽代谢、氮代谢、磷酸戊糖途径(PPP)、糖酵解/糖异生、氰氨基酸代谢、次生代谢产物和苯丙烷生物合成等途径.其中,谷胱甘肽代谢途径中有5个谷胱甘肽-S-转移酶(GST)差异丰度蛋白(DAP),选择其中差异变化最大的GSTU6用于Real-time PCR验证,其表达量显著增加,合成GSH前体物的GLN1-2以及Prx135的表达量也显著增加.[结论]甘露糖能增强谷胱甘肽清除活性氧能力,缓解小麦Cd胁迫,减少Cd转运.

To explore the beneficial effect of hydrogen sulfide (H2S) on the growth of wheat seedlings under Cd2+ stress, a wheat cultivar Sukemai 1 was used as the experimental material in this study.The effects of H2S (different concentrations of NaHS were served as H2S donor) on the growth and physiological changes of wheat seedlings under Cd2+ stress (CdCl2 concentration of 50 μmol·L-1) were studied through hydroponic method.The results showed that exogenous H2S significantly improved the plant height, shoot biomass, non-protein thiol content, photosynthetic pigment contents, net photosynthetic rate, chlorophyll fluorescence parameters including photosynthetic performance index of PS II, the absorption of light energy, trapped energy fluxes for reducing QA, the electron transport in PS II cross-section and non-photochemical quenching of wheat leaves under Cd2+ stress.Cd concentration in roots were also increased.While the content of antioxidants, such as malonaldehyde, hydrogen peroxide and superoxide anion in wheat leaves, Cd concentration in shoots, and Cd transport factor were significantly reduced by pretreatment of H2S on wheat seedlings under Cd2+ stress.In summary, the harmful effects of Cd2+ on wheat seedlings were mitigated by exogenous H2S through scavenging reactive oxygen free radicals in the leaves to decrease the destruction of photosynthetic pigments, to reduce the damage from peroxidation of membrane lipid, to protect the photosynthetic electron transfer system, to increase the heat dissipation, as well as to improve the photosynthetic capacity, and to alleviate the growth inhibition caused by Cd2+, and the optimal NaHS concentration was 50 μmol·L-1.

The objective of this study was to reveal the physiological and molecular mechanisms of low-nitrogen (N) tolerance in transgenic plant lines containing C4 phosphoenolpyruvate carboxylase (C4-PEPC) gene. The transgenic rice lines only over-expressing the maize C4-PEPC) (PC) and their untransformed wild type, Kitaake (WT), were used in this study. At different N levels, the dry weight, total N content, carbon and N levels, photorespiration-related enzymatic activities, gene expression levels and photorespiration-related product accumulations were measured, as were the transgenic lines' agronomic traits. The PC line, having lower total N and higher soluble sugar contents, was more tolerant to low-N stress than WT, which was consistent with its higher PEPC and lower N-assimilation-related enzyme activity levels. The photosynthetic parameters, enzymatic activity levels, transcripts and products related to photorespiration in PC were also greater than in WT under low-N conditions. This study showed that increased carbon levels in transgenic rice lines overexpressing C4-PEPC could help regulate the photorespiratory pathway under low-N conditions, conferring low-N tolerance and a higher grain yield per plant.

选取厦门地区具有代表性的城市公园绿地21处,调查固氮树种组成、分布并通过观察根系根瘤有无和固氮酶活性测定,对厦门40种园林树木的固氮能力进行了初步筛选,结果表明:刺桐、鸡冠刺桐、紫藤、印度紫檀、流苏相思、翅荚决明、黄花槐、红花洋金凤、常春油麻藤是适于我国南方的高效固氮树木,可配置用于厦门地区的园林绿化.

Ditch-buried straw return(DB-SR)is a novel soil tillage practice which forms a special"straw layer"structure. In order to elabo-rate the role of straw layer on soil nitrogen distribution and microbial community, a field experiment was conducted under DB-SR with three burial depths(20 cm:DB-SR-20;40 cm:DB-SR-40 and CK). NH+4-N, NO-3-N, microbial biomass carbon(MBC)and community level physiological profile(CLPP)were determined in the straw layer and its interface soil layers under different treatments. Results showed that the structure of"straw layer"had positive effect on nitrogen retentions. In DB-SR-20, the straw layer increased MBC at the interface of straw layer, but no significant effect was found for the functional diversity. In DB-SR-40, MBC decreased at first and then increased at the interface of rice straw layer, but the pattern was reversed for wheat straw layer. Microbial diversity index(H)increased for rice straw but decreased at first and then increased for wheat straw layer over time. CLPP suggested that the microorganisms of straw layer could utilize various carbon sources, and their metabolic activity was higher than CK. In DB-SR-20 for wheat straws, NH+4-N and NO-3-N were significantly related to variation of microbial community in the straw-soil interface, but MBC was correlated to the microbial community in the straw layers. In DB-SR-40, NH+4-N、NO-3-N and MBC were significantly correlated to the variation of microbial communities in the straw layers. This study sug-gested that the"straw layer"could effectively increase soil N retention, and increase the functional diversity of soil microbial community.

Based on the actual application in the biological field practice,Nanjing Agricultural University Virtual Simulation Experimental Teaching Center led to construct the virtual simulation training system in Tianmu Mountain biological field practice.This paper discusses the idea of constructing virtual experiment platform,implementation mode and application effect.This system makes full use of modern information technology,organic integrate simulation technology with experimental teaching,and gets the breakthrough of the weak points of traditional filed practice.Through the application of the platform,it can not only expand the capacity of teaching information,improve teaching efficiency,but also promote the reform and innovation of biological field practice teaching mode.

C4-phosphoenolpyruvate carboxylase (PEPC) gene (C4-pepc) plays a key role in C4 photosynthesis by catalyzing initial fixation of CO2 in C4 plants. To determine whether adenosine triphosphate (ATP) limits photosynthetic rate of transgenic rice plant with over-expressing maize C4-pepc, the second upper leaves of non-transgenic rice (WT) and transgenic rice with over-expressing maize C4-pepc (PC) were sprayed with 2 mmol·L?1 NaHSO3, 100 μmol·L?1 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) and 10 μmol·L?1 oligomycin at 5?6 leaf blade seedling stage under 20%(m/v) polyethylene glycol 6000 (PEG-6000) treatment. Then the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), PEPC activity, ATP content andΦPS?of PC and WT rice plants measured in the next morning. The results showed that 2 mmol·L?1 NaHSO3 enhanced Pn of the upper leaves of PC and WT rice seedlings without PEG-6000 treatment. However, the 100 μmol·L?1 DCMU and 10 μmol·L?1 oligomycin decreased Pn of the upper leaves of PC and WT rice seedlings without PEG-6000 treatment. Treatment with 2 mmol·L?1 NaHSO3 increased Gs and Ci of WT rice leaves but decreased Gs and Ci of PC rice leaves. While treatment with 100 μmol·L?1 DCMU increased Ci of PC and WT rice leaves, it decreased Gs of PC and WT rice leaves. PEG-6000 treatment decreased Pn of the upper leaves in PC and WT plants under different treatments. However, PEG-6000 treatment combined with 2 mmol·L?1 NaHSO3 solution spray retarded the decrease in Pn. Then PEG-6000 treatment combined with DCMU and oligomycin sprays increased the rate of Pn decline. After 8 hours of 20% PEG-6000 treatment combined with different solutions, Gs of PC rice leaves remained unchanged while Pn of PC rice leaves changed obviously. The results further showed that ATP content, PEPC activity andΦPS? content in rice leaves changed obviously under different treatments. While DCMU treatment accelerated the decrease in ATP content, PEPC activity and ΦPS? of PC and WT leaves, NaHSO3 retarded the rates of decrease in these elements. Although oligomycin decreased ATP content in rice leaves, it had no effect on ΦPSII in rice leaves. It was therefore concluded that PC maintained high levels of PS?activity and Pn stability by inducing more ATP in rice leaves compared with WT plants under drought stress.

Hydrogen sulfide (H2S) is considered to be the third gaseous signaling molecule after NO and CO, and it plays an active role in regulating the physiological processes of plants and animals. In this work, rice cultivar 'IIyou 084' seedlings were treated with NaHS, which is a donor of H2S, for 10 days, and its effects on growth and physiology, including photosynthesis, photorespiration, chlorophyll fluorescence, and stomata, were investigated. The data revealed that 0.01 mM of H2S improved rice biomass and chlorophyll content, while higher concentrations of H2S had an adverse effect on these parameters. Photosynthetic rate, stomatal conductance, and ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) activity also increased under 0.01 mM H2S treatment. However, photosynthetic oxygen evolution rate, photosynthetic electron transfer, and photochemical efficiency of PSII were not affected by H2S treatment. In addition, photosynthesis oxygen sensitivity, CO2 compensation point, and glycolate oxidase (EC 1.1.3.1) activity reduced by H2S treatment, and thus photorespiration was down-regulated. Under light, stomatal aperture and density increased by treatment with 0.01 mM H2S. On the basis of these results, it can be deduced that 0.01 mM of H2S treatment improved photosynthesis in rice by increasing its stomatal aperture and density, which may result from reduced photorespiration.

The objective of this study was to reveal transgenic rice with high expression of maize C 4-PEPC pho-tosynthetic performance under low nitrogen conditions,two rice genotypes including C 4-PEPC transgenic rice (PC) and untransgenic Kitaake rice(WT)in the pot experiments were chosen to measure their photosynthesis characteris-tics,SPAD values,PEPC,Rubisco,NR and GS activities of flag leaves at different flowering stage under different ni-trogen applications(normal nitrogen 300 kg /ha,low nitrogen 65 kg /ha)and their yield component were investigated after harvest.The results showed that the net photosynthetic rate of PC compared with WT were increased by 1 3.1 0% (P <0.05 )and 29.29% (P <0.05 ),respectively in the 1 4,28 d after flowering under low nitrogen treatment.At the same time,under low concentrations of nitrogen,relative to untransformed wild type rice,activity of Rubisco carboxylase of PC were increased by 67.86% and 52.63% (P <0.05)in the 1 4,28 d after flowering re-spectively,while activity of nitrate reductase of PC were increased 79.49% (P <0.05)and 1 7.96%.Meanwhile, activity of glutamine synthetase of PC was increased 28.48% (P <0.05)only in the 28 days after flowering com-paring with WT.But we did not find significant differences in the yield of PC and WT under low nitrogen condi-tions.Therefore,PC maintain high net photosynthetic rate by inducing the activity of carbon and nitrogen key en-zyme improvement under low nitrogen conditions.

细胞外ATP(extracellular ATP,eATP)是目前公认的细胞外信号分子,参与调控多种环境刺激下植物的生长、发育和防御反应.在植物细胞信号转导过程中,eATP具有双重功能,其作用主要取决于细胞外基质中eATP的浓度.eATP含量过高或者过低都会导致细胞死亡,适度水平的eATP则有助于植物的生长和发育.细胞外三磷酸腺苷双磷酸酶(Apyrase)严格控制细胞外基质中eATP的水平,因此有助于调控植物在逆境条件下的生长和防御反应.该文总结了植物中eATP的发现、产生和清除以及受体和信号转导等研究进展,重点论述eATP在逆境条件下的生理功能,并对植物eATP的研究方向作了展望.

We investigated the effects of exogenous spermidine (Spd) on growth, photosynthesis and expression of the Calvin cycle-related genes in cucumber seedlings (Cucumis sativus L.) exposed to NaCl stress. Salt stress reduced net photosynthetic rates (PN), actual photochemical efficiency of PSII (ΦPSII) and inhibited plant growth. Application of exogenous Spd to salinized nutrient solution alleviated salinity-induced the inhibition of plant growth, together with an increase in PN and ΦPSII. Salinity markedly reduced the maximum carboxylase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Vcmax), the maximal velocity of RuBP regeneration (Jmax), triose-phosphate utilization capacity (TPU) and carboxylation efficiency (CE). Spd alleviated the negative effects on CO2 assimilation induced by salt stress. Moreover, Spd significantly increased the activities and contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and fructose-1,6-biphosphate aldolase (ALD; aldolase) in the salt-stressed cucumber leaves. On the other hand, salinity up-regulated the transcriptional levels of ribulose-1,5-bisphosphate (RCA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribrokinase (PRK) and down-regulated the transcriptional levels of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (RbcL), ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RbcS), ALD, triose-3-phosphate isomerase (TPI), fructose-1,6-bisphosphate phosphatase (FBPase) and 3-phosphoglyceric acid kinase (PGK). However, Spd application to salt-stressed plant roots counteracted salinity-induced mRNA expression changes in most of the above-mentioned genes. These results suggest that Spd could improve photosynthetic capacity through regulating gene expression and activity of key enzymes for CO2 fixation, thus confers tolerance to salinity on cucumber plants.

Rice cultivar‘IIyou 084’ is our study material. We determined the rice’s photosynthesis, fast chloro-phyll lfuorescence induction curve (OJIP), the accumulation of O2ˉ· and H2O2 in rice leaf in strong light stress. The data revealed that rice’s photosynthesis and stomatal conductance were reduced; the proportion of the closed PSII reaction centers and the degree reduction of the primary quinone acceptor of PSII acceptor side in the electron transport chain (QA) were increased;the quantum yield of electron transfer and energy in PSII reac-tion center, and the ratio of energy which passed to the downstream electronics chain were declined;the trans-formation of excess energy of PSII to PSI under photoinhibition was declined;the production of free radicals was increased. While treated with exogenous sodium hydrosulifde (NaHS), a donor of hydrogen sulifde (H2S), these changes which have an negative effective on the activity of PS II were alleviated, especially can promote more energy transform from PSII to PSI, thus easing the over-reduction of PSII and improving the activity of PSII. These results illustrate that exogenous H2S can promote the photosynthetic activity of PSII to mitigate the damage caused by photoinhibition.

Results from our previous study suggested that haem oxygenase-1/carbon monoxide (HO-1/CO) acts as a downstream signal system in the auxin-induced pathway leading to cucumber (Cucumis sativus) adventitious root formation. The objective of this study was to test whether HO-1 is also involved in hydrogen sulfide (H2S)-induced adventitious root formation. Cucumber explants were treated with HO-1 inducer haemin and H2S donor sodium hydrosulfide (NaHS) in combination with the specific inhibitor of HO-1 zinc protoporphyrin IX (ZnPPIX), and their effects on cucumber adventitious root development in IAA-depleted explants were compared. The results showed that similar to inducible responses of haemin, NaHS brought about the induction of cucumber HO-1 transcripts (CsHO-1) and its protein levels, and thereafter adventitious root formation. A further experiment verified that H2S or HS- rather than other sulfur-containing components derived from NaHS was ascribed to the stimulation response. The inducible effect is specific for CsHO-1 because ZnPPIX significantly suppressed the above responses, and the inhibitory effects were reversed partially when 30% CO-saturated aqueous solution was added. Molecular evidence further suggested that the NaHS-triggered upregulation of target genes responsible for HO-1/CO-induced adventitious root formation, including CsDNAJ-1 and CsCDPK1/5, was inhibited significantly by ZnPPIX. These decreases were reversed obviously by the addition of CO aqueous solution. However, hypotaurine (HT), the H2S scavenger, could not influence the haemin- and CO-induced adventitious rooting in IAA-depleted cucumber explants. Together, the above results suggested that HO-1 was involved in H2S-induced cucumber adventitious root formation.

The effects of DIC levels on the photosynthesis of Ulva prolifera,carbon absorbing capacity at aquatic and aerial state,and pH value improving ability,were studied under laboratory conditions.The results show that the value of Km(DIC) for photosynthesis of U.prolifera is 0.25 mmol/dm3,and photosynthesis of U.prolifera is saturated at 1.2mmol/dm3 of DIC concentration in seawater,which is extremely lower than ambient DIC concentration(2.4 mmol/dm3,DIC) in normal seawater.It indicates that the blades in U.prolifera could keep a vigorous photosynthesis and growth during "green tide" blooming.In seawater,the blades of U.prolifera absorbed the DIC from seawater.Cultured with blade density of 0.5 g/dm3,the rate of carbon fixation of U.prolifera by photosynthesis is 10.92 mg/(g·d)(FW) for one photosynthesis period.Cultured for 5 d,the DIC concentration in 0.5,1.0 and 2.5 g/dm3 blade density groups decreases to 4.85,2.62 and 0.66 mg/dm3 respectively.It indicates that DIC uptaking rate increases with the blade density increase,and the DIC concentration removal rate is 77.78%,88.00% and 96.98% for 0.5,1.0 and 2.5 g/dm3blade density groups,respectively.When blades absorbed the DIC out of seawater,they immediately increased the pH in seawater,and the rate for pH increasing reached to 0.96 /(dm3·g·d) in culture system with 0.5 g/dm3 blade density during one photosynthesis period.Cultured for 5 d,the pH value in 0.5,1.0 and 2.5 g/dm3blade density groups increases to 9.1,9.2 and 9.7 in the first culture day respectively,and keeps at 9.9 in the 5th day.It indicates that the higher the blade density,the higher the pH in culture system.When exposed in air,the blades could absorb the CO2 from air.The rate of photosynthetic carbon fixation of U.prolifera in the air is about 46.14 mg/(g·d) during one photosynthesis period,and it is 4.23 times more than that in water.The photosynthesis carbon fixation efficiency for unit mass would decrease for shading among blades.It indicates that this study will provide the supports for green tide blooming mechanism study and estimating its CO2 emission reduction and ocean acidification prevention.