Effects of Different Arbuscular Mycorrhizal Fungi on Physiology of Viola prionantha under Salt Stress

Arbuscular mycorrhizal(AM)fungi distribute widely in natural habits and play a variety of ecological functions.In order to test the physiological response to salt stress mediated by different AM fungi,Viola prionantha was selected as the host,the dominant AM fungus in the rhizosphere of V.philippica growing in Songnen saline-alkali grassland,Rhizophagus irregularis,and their mixtures were used as inoculants,and NaCl stress was applied after the roots were colonized.The results showed that V.philippica could be colonized by AM fungi in the field and the colonization rate ranged from 73.33%to 96.67%,and Claroideoglomus etunicatum was identified as the dominant AM fungi species in the rhizosphere of V.philippica by morphology combined with sequencing for AM fungal AML1/AML2 target.Inoculation with both the species resulted in the formation of mycorrhizal symbiosis(the colonization rate was more than 70%)and AM fungi significantly enhanced plants’tolerance to salt stress of varying magnitude.Higher activity of antioxidant enzymes and augmented levels of proline and other osmoregulators were observed in AM plants.The content of MDA in CK was higher than that in the inoculations with the stress of 100,200,and 250 mM.All indices except soluble protein content and MDA content were significantly correlated with AM fungal colonization indices.The analysis for different AM fungal effects showed that the mixtures and R.irregularis worked even better than C.etunicatum.These results will provide theoretical support for the exploration and screening of salt-tolerant AM fungi species and also for the application of AM-ornamental plants in saline-alkali urban greening.

Physiological Responses of Clam(Ruditapes philippinarum)to Transport Modes with Different Temperatures

Given the increased circulation time after fishing,a series of changes take place in live clams,leading to a deterioration in quality even after death.Thus,in this study,we aimed to explore the optimal mode of transportation of clams.The container for holding clams was reformed,and a water circulation temperature control system was established.The physiological responses of clams during anhydrous and watery transportation at two temperatures(4 and 15℃)were investigated based on the aforementioned system.When comparing the transportation patterns after 3 d of transport,a higher survival rate was observed at 4℃(97%)than at 15℃(63%)in the anhydrous transportation groups and a lower survival rate was observed at 4℃(93%)than at 15℃(99%)in the watery transportation groups.In addition,the glycogen content,condition index(CI),and adenylate energy charge(A.E.C)value were higher at4℃((40.87±0.99)mg g^(-1),13.71%±0.50%and 57.45%±1.60%)than at 15℃((30.54±0.81)mg g^(-1),9.09%±0.30%and 43.12%±1.65%)in the anhydrous transportation groups.In the watery transportation groups,a lower glycogen content,CI,and A.E.C.value were observed at 4℃((33.78±0.84)mg g^(-1),9.78%±0.50%and 64.65%±1.25%)than at 15℃((41.53±0.93)mg g^(-1),12.72%±0.83%and 71.58%±1.27%).Results from this study show that anhydrous transportation(4℃)is the optimal transport condition for clams to maintain a high quality and good physiological conditions.Thus,this study will be particularly useful for establishing shellfish transportation systems.

Salt stress responses in foxtail millet:Physiological and molecular regulation

Foxtail millet(Setaria italica L.),a member of the Paniceae family,is a temperate and tropical grass species that is widely cultivated on the Eurasian continent.It is Chinese in origin and possesses a small genome,short growth cycle,and strong natural abiotic stress resistance.Elucidating the mechanism of millet tolerance to salt stress is becoming increasingly important with increasing soil salinization limiting crop productivity.The responses and mechanisms of tolerance to salt stress from other model plants such as Arabidopsis and rice,were compared with those from foxtail millet to summarize current research on responses to salt stress.Numerous processes are involved in these processes,including physiological reactions,sensing,signaling,and control at the transcriptional,post-transcriptional,and epigenetic levels.To increase crop productivity and agricultural sustainability,a variety of technologies can be used to investigate how salt tolerance is mediated by physiological and molecular processes in foxtail millet.

Seed Dormancy and Seedlings Physiological Response to Topramezone in Green Foxtail(Setaria viridis)

Green foxtail(Setaria viridis)is a notorious weed in corn fields in Heilongjiang Province.To investigate the best method to break the seed dormancy of green foxtail and its physiological response to topramezone,this study selected newly harvested and one-year stored green foxtail seeds as research subjects.The seeds were treated with HCl,Na OH,gibberellic acid(GA),different water temperatures and polyethylene glycol(PEG)to study the seed dormancy and drought resistance of green foxtail.The results showed that newly harvested seeds exhibited dormancy,and treatments with HCl,NaOH and different water temperatures were unable to break the dormancy.Soaking the seeds in GA could overcome dormancy,but the seeds failed to germinate when exposed to 25%PEG concentration.When topramezone was applied at rates of 22.5 and 45.0 g a.i.·hm^(-2)at the 3-leaf and 5-leaf stages,respectively,the chlorophyll content reached the lowest value at 28 days after treatment(DAT).At the 7-leaf stage,the chlorophyll content reached the lowest value at 7 DAT.The activity of 4-hydroxyphenylpy-ruvate dioxygenase(HPPD)enzyme after topramezone application reached the maximum value at 7 DAT for different leaf ages,and the higher the leaf age,the higher the HPPD activity,which was an important factor contributing to the resistance of green foxtail to topramezone.

Seed Storability in Rice: Physiological Foundations, Molecular Mechanisms, and Applications in Breeding

Long-term storage of crop seeds is critical for the conservation of germplasm resources, ensuring food supply, and supporting sustainable production. Rice, as a major food staple, has a substantial stock for consumption and production worldwide. However, its food value and seed viability tend to decline during storage. Understanding the physiological responses and molecular mechanisms of aging tolerance forms the basis for enhancing seed storability in rice. This review outlines the latest progress in influential factors, evaluation methods, and identification indices of seed storability. It also discusses the physiological consequences, molecular mechanisms, and strategies for breeding aging-tolerant rice in detail. Finally, it highlights challenges in seed storability research that require future attention. This review offers a theoretical foundation and research direction for uncovering the mechanisms behind seed storability and breeding aging-tolerant rice.

Salt tolerance in rice:Physiological responses and molecular mechanisms

Crop yield loss due to soil salinization is an increasing threat to agriculture worldwide.Salt stress drastically affects the growth,development,and grain productivity of rice(Oryza sativa L.),and the improvement of rice tolerance to salt stress is a desirable approach for meeting increasing food demand.The main contributors to salt toxicity at a global scale are Na^(+)and Cl^(-)ions,which affect up to 50%of irrigated soils.Plant responses to salt stress occur at the organismic,cellular,and molecular levels and are pleiotropic,involving(1)maintenance of ionic homeostasis,(2)osmotic adjustment,(3)ROS scavenging,and(4)nutritional balance.In this review,we discuss recent research progress on these four aspects of plant physiological response,with particular attention to hormonal and gene expression regulation and salt tolerance signaling pathways in rice.The information summarized here will be useful for accelerating the breeding of salt-tolerant rice.

Growth and physiological responses of Agriophyllum squarrosum to sand burial stress

Agriophyllum squarrosum is an annual desert plant widely distributed on mobile and semi-mobile dunes in all the sandy deserts of China. We studied the growth and physiological properties of A. squarrosum seedlings under different sand burial depths in 2010 and 2011 at Horqin Sandy Land, Inner Mongolia to understand the ability and mechanism that A. squarrosum withstands sand burial. The results showed that A. squarrosum had a strong ability to withstand sand burial. Its survival rate, plant height and biomass increased significantly at a burial depth 25% of seedling height and decreased significantly only when the burial depth exceeded the height of the seedlings; some plants still survived even if the burial depth reached 266% of a seedling height. The malondialdehyde （MDA） content and membrane permeability of the plant did not change significantly as long as the burial depth was not greater than the seedling height; lipid peroxidation increased and cell membranes were damaged if the burial depth was increased further. When subjected to sand burial stress, superoxide dismutase （SOD） and peroxidase （POD） activities and free proline content increased in the seedlings, while the catalase （CAT） activity and soluble sugar content decreased. Sand burial did not lead to water stress. Reductions in photosynthetic area and cell membrane damage caused by sand burial may be the major mechanisms increasing mortality and inhibiting growth of the seedling. But the increases in SOD and POD activities and proline content must play a certain role in reducing sand burial damage.

Physiological response of flag leaf and yield formation of winter wheat under different spring restrictive irrigation regimes in the Haihe Plain,China

In order to identify the optimum period of spring water-restrictive irrigation for winter wheat(Triticum aestivum L.)in the Haihe Plain,China and elucidate its effects on flag leaf senescence and yield formation,field experiments were conducted at the Xinji Experimental Station of Hebei Agricultural University from 2016 to 2019 by using different irrigation regimes in spring,including the conventional regime involving two irrigation periods(control(CK),the 3-leaf unfolding stage and the anthesis stage)and a series of single,restrictive irrigation regimes(SRI)comprising irrigation at the 3-leaf unfolding stage(3 LI),4 LI,5 LI,and 6 LI.There are five major findings:(1)The senescence(determined by the green leaf area,GLA)in the 4 LI treatment occurred moderately earlier than that in CK,showed no significant difference with that in 5 LI and 6 LI,and occurred significantly later than that in 3 LI.(2)Compared with other SRI treatments,the GLA value and photosynthetic rate in 4 LI were 14.82 and 20.1%higher,respectively.Microstructural analysis of flag leaf also revealed that the mesophyll cells and chloroplasts were irregularly arranged under drought stress in 3 LI and 6 LI;however,drought stress had minimal negative effects on the microstructure in 4 LI and 5 LI.(3)Postponed irrigation in spring could significantly increase superoxide dismutase(SOD)and catalase(CAT)activities in the early stage of grain filling;however,these activities would subsequently decrease.Among the four SRI treatments,the overall enzyme activities were the highest in 4 LI,and the combined malondialdehyde(MDA)content in flag leaves in 4 LI and 5 LI was 14.5%lower on average than that in 3 LI and 6 LI.(4)The soluble sugar(SS)and proline(Pro)contents in 4 LI were the highest among the four SRI treatments;however,they were lower than those in CK.The abscisic acid(ABA)hormone content in 4 LI and 5 LI was lower than that in 3 LI and 6 LI,respectively,suggesting a smaller drought stress effect in 4 LI and 5 LI.(5)In two growing seasons,there was a larger number of spikes per unit area in 4 LI(i.e.,13.4%higher than that in 5 LI and 6 LI)and the 1000-grain weight in 4 LI was the highest among the four SRI treatments(i.e.,6.0%higher than that in the other three SRI treatments).Therefore,a single restrictive irrigation regime at the 4-leaf unfolding stage is recommended to be effective in slowing down the senescence process of flag leaves and achieving high yield.

The Physiological and Molecular Responses of Arabidopsis thaliana to the Stress of Oxalic Acid

Many fungal phytopathogens can secrete oxalic acid （OA）, which is the crucial pathogenic determinant and plays important roles in pathogenicity and virulence of pathogen during infection process. However, how plants respond to OA stress still needs further characterization. In this study, we observed the physiological and molecular responses of Arabidopsis thaliana to OA stress. The leaves of 6-wk-old A. thaliana were sprayed with OA and distilled water respectively, and 0, 2, 4, 8, 12, and 24 h later, the leaves were collected and the contents of MDA, H2O2, and GSH, and the activities of CAT, SOD, and POD were determined and the expressions of PR1 and PDF1.2 were also studied. Under the stress of 30 mmol L-1 OA, SOD activity was first enhanced to reduce the accumulation of O2.-. But immediately, POD, CAT, and GSH all decreased extremely resulting in the accumulation of H2O2, and the MDA content increased 24 h later. GSH activity was enhanced significantly at 24 h after OA used. However, H2O2 wasn＇t eliminated at the same time, suggesting that the activity inhibitions of POD and CAT might be the reasons that caused Arabidopsis cells＇ impairment under OA stress. RT-PCR results indicated that PDF1.2, a marker gene of the JA/ET signaling was significantly induced; PR1, an indicator gene in SA signaling, was slighlty induced from 8 to 12 h after OA stress. In conclusion, Arabidopsis may recruit metabolism of reactive oxygen, both JA/ET and SA signaling pathways to respond to OA stress. These results will facilitate our further understanding the mechanisms of plant response to OA and OA-dependent fungal infection.

Effects of oxygen concentration and flow rate on cognitive ability and physiological responses in the elderly

The supply of highly concentrated oxygen positively affects cognitive processing in normal young adults. However, there have been few reports on changes in cognitive ability in elderly subjects following highly concentrated oxygen administration. This study investigated changes in cognitive ability, blood oxygen saturation （%）, and heart rate （beats/min） in normal elderly subjects at three different levels of oxygen [21% （1 L/min）, 93% （1 L/min）, and 93% （5 L/min）] administered during a 1-back task. Eight elderly male （75.3 ＋ 4.3 years old） and 10 female （71.1 ＋ 3.9 years old） subjects, who were normal in cognitive ability as shown by a score of more than 24 points in the Mini-Mental State Examination-Korea, participated in the experiment. The experiment consisted of an adaptation phase after the start of oxygen administration （3 minutes）, a control phase to obtain stable baseline measurements of heart rate and blood oxygen saturation before the task （2 minutes） and a task phase during which the 1-back task was performed （2 minutes）. Three levels of oxygen were administered throughout the three phases （7 minutes）. Blood oxygen saturation and heart rate were measured during each phase. Our results show that blood oxygen saturation increased, heart rate decreased, and response time in the 1-back task decreased as the concentration and amount of administered oxygen increased. This shows that administration of sufficient oxygen for optimal cognitive functioning increases blood oxygen saturation and decreases heart rate.

Size-and leaf age-dependent effects on the photosynthetic and physiological responses of Artemisia ordosica to drought stress

Drought is one of the most significant natural disasters in the arid and semi-arid areas of China.Populations or plant organs often differ in their responses to drought and other adversities at different growth stages.At present,little is known about the size-and leaf age-dependent differences in the mechanisms of shrub-related drought resistance in the deserts of China.Here,we evaluated the photosynthetic and physiological responses of Artemisia ordosica Krasch.to drought stress using a field experiment in Mu Us Sandy Land,Ningxia Hui Autonomous Region,China in 2018.Rainfall was manipulated by installing outdoor shelters,with four rainfall treatments applied to 12 plots(5 m×5 m).There were four rainfall levels,including a control and rainfall reductions of 30%,50%and 70%,each with three replications.Taking individual crown size as the dividing basis,we measured the responses of A.ordosica photosynthetic and physiological responses to drought at different growth stages,i.e.,large-sized(>0.5 m^(2))and small-sized(≤0.5 m^(2))plants.The leaves of A.ordosica were divided into old leaves and young leaves for separate measurement.Results showed that:(1)under drought stress,the transfer efficiency of light energy captured by antenna pigments to the photosystem II(PSII)reaction center decreased,and the heat dissipation capacity increased simultaneously.To resist the photosynthetic system damage caused by drought,A.ordosica enhanced its free radical scavenging capacity by activating its antioxidant enzyme system;and(2)growth stage and leaf age had effects on the reaction of the photosynthetic system to drought.Small A.ordosica plants could not withstand severe drought stress(70%rainfall reduction),whereas large A.ordosica individuals could absorb deep soil water to ensure their survival in severe drought stressed condition.Under 30%and 50%rainfall reduction conditions,young leaves had a greater ability to resist drought than old leaves,whereas the latter were more resistant to severe drought stress.The response of A.ordosica photosynthetic system reflected the trade-off at different growth stages and leaf ages of photosynthetic production under different degrees of drought.This study provides a more comprehensive and systematic perspective for understanding the drought resistance mechanisms of desert plants.

Physiological and Molecular Analyses of Low-Salinity Stress Response in the Cuttlefish(Sepia pharaonis)Juveniles

As a stenohaline species,the survival of Sepia pharaonis can be affected by salinity significantly.This study aimed to explore the function of decreasing salinity on the survival of Sepia pharaonis,which can provide an advanced production guide on the culture of S.pharaonis in the rainy season.Salinity was gradually decreased from 29 to 22 within 48 h to acclimate S.pharaonis to a low-salinity environment.After ten days of breeding under low-salinity of 22,the death rate was high.In this process,changes in tissue and cell structures in the larval liver,biochemical indicators,and osmoregulation-related gene expression were examined.In-terestingly,hepatocytes in the low-salinity group were irregular,had dissolved tissue inclusions,and contained vacuolized cells.There-fore,low salinity caused severe damages at a cellular level that can elevate the mortality rate.A gradual decline in salinity limited the full adaptation of S.pharaonis.Biochemical indicators and osmoregulation-related gene expression changed similarly.For instance,the trend of malondialdehyde(MAD)as a product of lipid peroxidation reflected the degree of damage to the body by free radicals.The antioxidant system of S.pharaonis could cope with oxidative stress caused by the change in salinity to a certain extent.Osmo-regulation-related genes’expression also showed an optimistic result,that is,S.pharaonis responded positively to the change in sali-nity by adjusting the expression of osmoregulation-related genes.Conversely,the increase in mortality at day 10 also proved the weak adaptation capability of S.pharaonis.This study indicated that S.pharaonis can adapt to a low-salinity environment with a li-mited extent.

Effects of sand burial on survival and growth of Artemisia halodendron and its physiological response

There is a great deal of literature on the effects of sand burial upon the survival and growth of desert plants, but the physiological adaption mechanisms of desert plants to sand burial have as yet rarely been studied. Artemisia halodendron is widely distributed in the semi-arid deserts of China and is a dominant species in semi-moving dune vegetation. The growth and physiological properties ofA. halodendron seedlings under different sand burial depths were studied in 2010 and 2011 in the Horqin Sand Land, Inner Mongolia, to better understand the ability and physiological mechanism by which desert plants withstand sand burial. The results showed that A. halodendron as a prammophyte species had a stronger ability to withstand sand burial compared to non-prammophytes, with some plants still surviving even if buried to a depth reaching 225% of seedling height. Although seedling growth was inhibited significantly once the depth of sand burial reached 50% of the seedling height, seedling survival did not decrease significantly until the burial depth exceeded 100% of the seedling height. Sand burial did not result in significant water stress or MDA （Malondialdehyde） accumulation in the seedlings, but membrane permeability increased significantly when the burial depth exceeded 100% of the seedling height. After being subjected to sand burial stress, POD （Peroxidase） activity and proline content increased significantly, but SOD （Superoxide Dismutase） and POD activities and soluble sugar content did not. The primary mechanism resulting in in- creased mortality and growth inhibition were that cell membranes were damaged and photosynthetic area decreased when subjected to the severe stress of sand burial, while proline and POD played key roles in osmotic adjustment and protecting cell membranes from damage, respectively.

Physiological responses of seedlings of two oak species to flooding stress

The physiological responses of 2-year-old seedlings of Nuttall＇s oak （Quercus nuttallii） and Southern red oak （Q.falcata） with two treatments i.e., deep-drowning and shallow-drowning, were studied. Taxodium distichum was selected as a control. The survival rates of seedlings were calculated, the photosynthetic indices were detected by Licor-6400 photosynthetic system instrument, and the root activities of seedlings were tested by the method of triphenyltetrazolium chloride （TTC）. Results showed that： 1） By experiencing flooding for 76 d and recovering for 60 d after water was drained off, all seedlings survived under the shallow-drowning treatment. None of Q. falcata seedlings died in the deep-drowning treatment until the 49th day. The survival rate of Q. falcata in the deep-drowning treatment was 30%. 2） Within 61 d of waterlogging treatments, the net photosynthetic rate （Pn）, stomatal conductance （gs） and transpiration rate （Tr） showed a tendency of declining, but intercellular concentration of CO2 （Ci） increased. With the prolongation of flooding stress, the extents of variation for all indices under deep-drowning treatment were larger than those under the shallow-drowning treatment. The variation of Q. falcata in flooding stress was larger than that of Q. nuttallii. 3） The root vigor and alcohol dehydrogenase （ADH） activities were detected at the 61st day in flooding stress. Waterlogging obviously inhibited root activities. Shallow-drowning made root vigor of Q. nuttallii decreased by 11.7%, and for Q. falcata, by 51.88%. Shallow-drowning treatment had no remarkable effects on ADH activities of seedlings, but deep-drowning increased those of Q. nuttallii seedlings by 227.24%, and decreased those of Q. falcata seedlings by 59.22% in the meantime. We conclude that Q. nuttallii had a stronger waterlogging resistance than Q. falcata, but weaker than T. distichum.

Physiological Response and Transcriptome Analysis of Cotton Leaves under Low Temperature Stress at the Two-leaf Stage

[Objectives]To investigate the effect of low temperature treatment on cotton leaves at the two-leaf stage.[Methods]Two cotton varieties(CN01 and SJB016(low temperature-tolerant))were used as the trial materials.They were treated at 25(CK)and 12℃(low temperature)for 0,3,6,12,24,48 and 72 h,respectively.Then,the changes in the contents of MDA,SS and Pro in the cotton leaves were analyzed.Based on the analysis results,RNA-seq verification was performed.[Results]Two cotton varieties(CN01 and SJB016(low temperature-tolerant))were used as the trial materials.They were treated at 25(CK)and 12℃(low temperature)for 0,3,6,12,24,48 and 72 h,respectively.Then,the changes in the contents of MDA,SS and Pro in the cotton leaves were analyzed.Based on the analysis results,RNA-seq verification was performed.[Conclusions]These genes may play an important role in improving the cold resistance of cotton.

Rice Curled Its Leaves Either Adaxially or Abaxially to Combat Drought Stress

Leaf rolling(LR)is one of the defensive mechanisms that plants have developed against adverse environmental conditions.LR is a typical drought response,promoting drought resistance in various gramineae species,including wheat,maize,and rice.Rice cultivation faces the formidable challenge of water deprivation because of its high water requirements,which leads to drought-related symptoms in rice.LR is an important morphological characteristic that plays a key role in controlling water loss during water insufficiency,thereby regulating leaf area and stature,which are crucial agronomic traits determining yield criteria.Bulliform,sclerenchyma,mesophyll,and vascular bundles are the cells that engage in LR and commonly exhibit adaxial or abaxial types of rolling in rice.The specific genes linked to rolling,either adaxially or abaxially,are discussed here.In addition to the factors influencing LR,here is a short review of the morphological,physiological and molecular responses of this adaptation under drought stress.Moreover,this review highlights how LR combats the consequences of drought stress.The eco-physiological and molecular mechanisms underlying this morphological adaptation in rice should be further explored,as they might be useful in dealing with various degrees of drought tolerance.

Growth,ROS Markers,Antioxidant Enzymes,Osmotic Regulators and Metabolic Changes in Tartary Buckwheat Subjected to Short Drought

Tartary buckwheat(Fagopyrum tataricum)is an important pseudocereal feed crop with medicinal and nutritional value.Drought is one of the main causes of reduced growth and yield in these plants.We investigated the growth,physiological,and metabolic responses of the widely promoted Tartary buckwheat variety Chuan Qiao No.1 to polyethylene glycol(PEG)-mediated drought stress.Drought significantly decreased shoot length,shoot biomass and relative water content.Root length,malondialdehyde content,electrolyte leakage,activities of superoxide dismutase,peroxidase,catalase and amylase,and contents of soluble sugar,soluble protein and proline were increased by PEG-mediated drought.Untargeted metabolomics analysis identified 32 core metabolites in seedlings subjected to PEG-mediated drought,16 of which increased—including quercetin,isovitexin,cyanidin 3-O-beta-D-glucoside,L-arginine,and glycerophosphocholine,while the other 16 decreased—including 3-methoxytyramine,2,6-diaminopimelic acid,citric acid,UDP-alpha-D-glucose,adenosine,keto-D-fructose.The 32 core metabolites were enriched in 29 metabolic pathways,including lysine biosynthesis,citrate(TCA)cycle,anthocyanin biosynthesis,and aminoacyl-tRNA biosynthesis.Among them,taurine and hypotaurine metabolism,flavor and flavor biosynthesis,indole alkaline biosynthesis,and alanine,aspartate and glutamate metabolism were the four main metabolic pathways affected by drought.Our findings provide new insights into the physiological and metabolic response mechanisms of Tartary buckwheat to drought stress.

Light shading improves the yield and quality of seed in oil-seed peony(Paeonia ostii Feng Dan)

Tree peony seed is unique for its super-high content of unsaturated fatty acid and is thus considered as an important source of woody oil. However, photosynthetic production is greatly reduced under high light intensity and air temperature during the seed filling period, which negatively affects seed yield and quality. The objective of this study was to determine if appropriate shading improves yield and quality of seed in oilseed peony. In this study, oilseed peony trees were shaded by different density polyethylene nets from four weeks after flowering to harvest stages to form light, moderate, and severe shadings, equivalent to about 80, 40, and 20% of full solar exposure, respectively. The effects of different shadings on some physiological parameters, yield and yield components, and nutritional composition of seed were examined. Averaged across two years, light shading increased the actual net photosynthetic rate（P_n） by 16.8%, the maximum net photosynthetic rate（P_（max）） by 81.4%, chlorophyll（Chl） content by 52.8%, auxin（IAA） content by 38.1%, and gibberellic acid（GA_3） content in leaves by 6.3%; it decreased the accumulation of H_2O_2 in leaves by 24.8%, malondialdehyde（MDA） by 22%, and endogenous abscisic acid（ABA） by 8.8%, indicating that leaf senescence in late season was considerably delayed. Light shading increased seed yield, and contents of crude fat and unsaturated fatty acids by 9.7, 5.6, and 9.6%, respectively, while moderate or severe shading significantly reduced all the three parameters. Light shading increased seed weight, but moderate or severe shading reduced seed weight or follicle density. The improved seed yield under light shading was mainly due to increased seed weight, while the reduced seed yield under moderate or severe shading was mainly attributed to reduce follicle density and seed weight. The improved seed weight and content of unsaturated fatty acids under light shading was possibly due to the delayed leaf senescence. The overall results indicated that light shading is beneficial to yield and quality parameters of seed in oilseed peony. Cultivating oilseed peony under a light shading environments such as partially closed forests would better increase total output and income per unit land area than that under full solar exposure.

Exogenous application of succinic acid enhances tolerance of Larix olgensis seedling to lead stress

Larix olgensis A. Henry(Changbai larch) is a productive commercial species and good candidate for afforestation in northeast China. It is widely planted in lead-stressed soils which can induce oxidative damage in this plant. Increasing tolerance to lead(Pb) stress is therefore of keen interest. A greenhouse experiment was conducted to identify the biomass, physiological responses and Pb accumulation of L. olgensis seedlings to Pb stress under succinic acid(SA) application and to explore the interaction of exogenous SA applications and stress resistance. L. olgensis seedlings were planted in Pb-stressed or unstressed haplic cambisols in pots. In Pb-contaminated soils the seedlings were treated daily with concentrations of SA solutions at a rate approximately equivalent to 0, 0.04,0.2, 1.0, or 2.0 mmol kg-1of soil for 10, 20, and 30 days,respectively. Pb treatment induced damage in the seedlings and led to the inhibition of biomass accumulation in roots,stems and leaves, and a rise in Pb accumulation in fine roots and leaves. Malondialdehyde(MDA) content and electrolyte leakage in leaves significantly increased while peroxidase(POD) activities, soluble protein and photosynthetic pigment contents in leaves were all reduced.Physiological toxicity was promoted with increasing Pb treatment times. When Pb-stressed seedlings were exposed to SA(especially 10.0 mmol L-1 over 20 days), the physiological responses for Pb-only were reversed and the biomass of roots, stems, and leaves dramatically increased.SA facilitated Pb uptake in fine roots and leaves but more Pb accumulated in fine roots. The results demonstrate that exogenous SA alleviates Pb-induced oxidative injuries and improves the tolerance of L. olgensis seedlings to Pb stress.

Effects of sand burial on dune plants: a review

Burial of different growth stages of plants （e.g., adult plants, seedlings and seeds） is frequent in dune ecosystems. The soil micro-environment, which differs from surface conditions, influences the survival and growth of dune plants. To sum up knowledge about the survival mechanisms of plants under sand burial and to promote practical rehabilitation of dune vegetation, we reviewed relevant published literature and concluded that： （1） Focus in recent years has been on impacts of sand burial on seed germination and seedling emergence. Generally, shallow burial increased seed germination and seedling emergence, but deeper burial was negative. Buried at the same depth, large seeds showed higher germination and seedling emergence rates, attributed to larger energy reserves. （2） Survival, growth and reproduction rates of dune plants show plasticity in response to sand burial. Long-term deep burial is fatal because it creates a physical barrier which overcomes the vertical growth of plants, reduces photosynthetic leaf area, and limits oxygen availability to roots. Modest burial, on the other hand, is advantageous for growth and reproduction of many dune plants, due to protection from excessive temperature and drought. （3） There are few reports concerning effects of sand burial on plant physiology, but a limited number of studies indicate that partial burial increases water use efficiency, chlorophyll content, transpiration rate and net photosynthetic rates. The antioxidant protective enzyme system and osmolyte balance were reported to be involved in the mechanisms of dune plant resistance to burial.