Effects of Soaking Cultivated Rice Seeds with Fulvic Acid on Physiological and Ecological Properties of Weedy Rice

[Objective] This study aimed to investigate the effects of soaking cultivated rice seeds with fulvic acid （FA） on physiological and ecological properties of weedy rice in the direct seeding cultivated rice field. [Method] Weedy rice JS-Y1 and culti-vated rice Nanjing 44 were used as experimental materials for field plot trials to an-alyze the effects of soaking cultivated rice seeds with 0 （water as control）, 4, 6, 8 g/L FA on til ering dynamics, plant height, chlorophyl content, photosynthetic perfor-mance, gas exchange parameters and yield components of weedy rice at different growth stages. [Result] Among the 4 plants/m2 weedy rice plots, with the increase of FA concentration, til er number, plant height, chlorophyl content, net photosynthetic rate （Pn）, stomatal conductance （Gs） and transpiration rate （Tr） of weedy rice were reduced. Under the 4-6 g/L FA concentration, til er numbers of weedy rice at differ-ent growth stages were reduced by 13.84%-35.71% compared with control at the same density and the most significant reduction was on the 22nd d after weedy rice germination; chlorophyl contents of weedy rice at the jointing stage were significant-ly reduced by 7.90%-8.88%. Furthermore, in the plots with 4 g/L FA, weedy rice plant heights at the heading stage and grain fil ing stage were significantly reduced by 6.37%-9.10%; Pn, Gs and Tr of weedy rice at the jointing stage and grain fil ing stage were significantly reduced by 10.19%-16.05%, 12.57%-23.33% and 10.28%-19.76%, respectively; 1 000-grain weight, effective panicle number per plant and panicles weight per plant of weedy rice at the maturity stage were significantly re-duced by 3.19%, 21.21% and 27.27%, correspondingly. [Conclusion] In 4 plants/m2 weedy rice plots, because soaking cultivated rice seeds with 4 g/L FA could regu-late the growth and development of cultivated rice, the soaking with FA could change the ecological relationship between cultivated rice and weedy rice, affect weedy rice physiological and ecological properties and al eviate the competitive inhi-bition of weedy rice on cultivated rice.

Remote Sensing Study of Gold Biogeochemical Effects in the Western Guangdong-Hainan Region——A Case Study of the Hetai Gold Deposit

The vegetation has been poisoned by gold in the western Guangdong-Hainan region. The gold content ofthe leaves there is as high as 10-1961 times the abundance, the chlorophyll content is 10%-30% lower thanthat of the vegetation in metamorphic terrains and 10%-20% higher than that in granite terrains, and thecarotenoid content is 10%-44% lower than the background value. The water content of leaves is 10% to 20%lower than the background value. The cells of leaves are deformed and broken. The leaf surface shows colourspots and becomes yellow or dark green. The spectral reflectance of the leaf surface is 5%-30% higher than thebackground value: the spectral shape has shifted 5-15 nm to the short wavelength. The gray scales of eanopyon images of Landsat TM and airborne imaging scanner (AIS) are 10%-100% higher than the backgroundvalues. On Landsat TM and AIS false colour images, plants poisoned by gold display a yellow color, whichdisinguishes them from background plants. According to the spectral and image features of goldbiogeochemical effects, the author has constructed a gold information system and expert prediction system,and thus two gold target areas and two gold prospect areas have been identified rapidly, economically andaccurately in the western Guangdong-Hainan region which is extensively covered by vegetation.

Sex-specific strategies of resource utilization and determining mechanisms of Hippophae rhamnoides in response to community succession

The dioecious plant,Hippophae rhamnoides,is a pioneer species in community succession on the Qinghai-Tibet Plateau(QTP),plays great roles in various ecosystem services.However,the males and females of the species differ both in their morphology and physiology,resulting in a change in the ratio of male to female plants depending on the environment.To further explore the functional traits critical to this sex-based distinctive response in the alpine grassland,we have surveyed the sex ratios,measured their photosynthetic parameters,height,leaf area and biomass allocation.The results showed that(i)The males had higher Pn,light saturation point,apparent quantum efficiency,A_(max) and lower water-use efficiency(WUE),which exhibited higher utilization efficiency or tolerance to strong light,while the females indicated higher utilization efficiency for low light and water.And it showed sex-specific biomass allocation patterns.(ii)H.rhamnoides populations across the successional stages all showed a male-biased sexual allocation,which was closely related to sex-specific WUE,Pn,root biomass/total biomass and root-crown ratio.(iii)The leaf traits of H.rhamnoides changed from higher N_(area),P_(area) and leaf mass per area in the early and late to lower in the middle,which meant they moved their growth strategy from resource rapid acquisition to conservation as the succession progressed.(iv)The increasing soil total phosphorus mostly contributed to regulating the sex bias of populations and variations of traits during the succession.The results are vital for the management of grassland degradation and restoration due to shrub encroachment on the QTP.

Physiological responses of four herbaceous plants to aluminum stress in South China

Different plants have physiological responses under Al stress,but there is no systematic study to examine physiological responses of herbaceous plants under Al stress.The aim of this study is to investigate the effect of Al on physiological characteristics of four herbaceous plants,which distributed in red soil area in South China,and to analyze the differences in physiological responses to Al stress between the four herbaceous plants.Four herbaceous plants(Pharbitis nil,Cassia occidentlis,Echinochloa colonum and Aeschynomene indica)were used,and the seed germi-nation percentage,the contents of chlorophyll,proline,and malondialdehyde(MDA),membrane permeability(MP),soluble sugar,and activities of peroxides(POD)and cata-lase(CAT)in leaves under five Al^(3+)treatments(0,80,400,2000,and 10000 mg/L)were assayed with the sand culture method.The results showed remarkable effects of Al^(3+)on physiological characteristics of these four herbaceous plants.The seeds of all the four species could not germinate at 10000 mg/L,and the growth of all plants were retarded under the 2000 mg/L Al^(3+)treatment.Compared with the control,2000 mg/L Al^(3+)significantly(P<0.05)reduced the con-tents of chlorophyll a and chlorophyll a+b,and increased the contents of MDA and MP.The content of proline in-creased very significantly(P<0.01)and activities of POD and CAT were depressed.The contents of MDA and MP in leaves of P.nil and A.indica decreased,and the activities of POD and CAT in leaves of the two plants increased under 80 mg/L and 400 mg/L.However,the changes in C.occidentlis leaves were opposite to those of the above two plants.The changes in leaves of E.colonum were similar to those of P.nil and A.indica at 80 mg/L,but were opposite to those at 400 mg/L Al^(3+).It is suggested that plants with higher ac-tivities of POD and CAT,more contents of chlorophyll and proline,and lower contents of MDA and MP consequently improve the tolerance to Al stress under low and middle Al treatments.

Elemental allelopathy by an arsenic hyperaccumulating fern,Pteris vittata L.

Aims the functional advantages of arsenic(As)hyperaccumulation by plants are poorly understood.One proposed benefit,termed ele-mental allelopathy,occurs when hyperaccumulated As is cycled from the plant back into the top layer of soil,allowing As hyperaccu-mulators to gain an advantage over intolerant species by increasing soil As concentrations([As])underneath their canopy.to date,there are no studies that detail the presence of increased soil[As]associ-ated with As hyperaccumulators.In this study,we documented vari-ation in the soil[As]associated with the Chinese brake fern,Pteris vittata L.and also compared the effects of environmentally relevant soil and solution[As]on competitor plant growth.Methods Four populations of P.vittata were identified in central Florida,USA.P.vittata tissue samples and soil samples were collected at the base of and at 3 m away from ferns in each population(n=36).Five sample locations were randomly selected from each site,and soils from the base and 3 m away from each fern were collected to examine the effects of naturally occurring soil[As]on the germination and growth of a potential competitor plant(Oxalis stricta).Solutions with increasing[As]were also used to examine the threshold for negative effects of[As]on O.stricta growth.[As]were measured using inductively coupled plasma mass spectrometry(ICP-MS).Important Findings Overall,soil[As]from the base of ferns was nearly twice that of soil 3 m away indicating that ferns hyperaccumulate As.However,ferns and their associated soil,contained different[As]depending on their col-lection site,indicating that these populations accumulate and use[As]differently.O.stricta growth decreased and germination was delayed as solution and soil[As]increased.However,the relative distance from the fern that the soil was collected from did not affect growth,which would be expected with elemental allelopathy.Our results show that P.vittata is associated with higher soil[As]and these concentrations are sufficient to inhibit growth of competitors.However,the absence of a strong inhibitory relationship associated with proximity to the fern across all locations suggests that the possible functional advantages of elemental allelopathy may depend on site specific characteristics.

A 60-year journey of mycorrhizal research in China:Past,present and future directions

The significance of mycorrhizas(fungal roots in 90% of land plants) in plant nutrient acquisition and growth,element biogeo-chemical cycling and maintaining of terrestrial ecosystem structures has been globally established for more than 120 years.Great progress in mycorrhizal research in the past 60 years(1950-2009,1981-2009 in particular) has also been made across China,particularly in the mainland,Hong Kong and Taiwan.For instance,a total of 20 new and ~120 records of arbuscular mycorrhizal(AM) fungal species,30 new and ~800 records of ectomycorrhizal(EM) fungal species,a dozen of new and ~100 records of orchid mycorrhizal(OM) fungal species have been isolated by morphological observation and/or molecular identification in China since the 1950s.Great accomplishment has also been made in the following area,including fungal species richness and genetic structure,relationships between species composition and plant taxa,effects of mycorrhizal fungi on plant nutrient uptake and growth,resistances to pathogens and interactions with other soil microorganisms,potential of mycorrhizal fungi in phytoremediation and/or land reclamation,alterations of enzymatic activities in mycorrhizal plants,and elevated CO2 and O3 on root colonization and species diversity.Unfortunately,the international community cannot easily appreciate almost all Chinese mycorrhizal studies since the vast majority of them have been published in Chinese and/or in China-based journals.The aim of this review is to make a comprehensive exposure of the past and present China's major mycorrhizal research to the whole world,and then to suggest potential directions for the enhancement of future mycorrhizal research within and/or between the Chinese and international mycorrhizal community.