Regulation of the growth of sprouting roots of black locust seedlings using root barrier panels

How can we regulate an invasive alien species of high commercial value?Black locust(Robinia pseudoacacia L.)has a unique capacity for seed dispersal and high germination.Field surveys indicate that black locust increases its growing area with sprouting roots and the elongation of horizontal roots at a soil depth of 10 cm.Therefore,a method to regulate the development of horizontal roots could be eff ective in slowing the invasiveness of black locust.In this study,root barrier panels were tested to inhibit the growth of horizontal roots.Since it is labor intensive to observe the growth of roots in the fi eld,it was investigated in a nursery setting.The decrease in secondary fl ush,an increase in yellowed leafl ets,and the height in the seedlings were measured.Installing root barrier panels to a depth of 30 cm eff ectively inhibit the growth of horizontal roots of young black locust.

Testing phaeophytinization as an index of ozone stress in trees

Ground-level ozone pollution is a menace for vegetation in the northern hemisphere,limiting photosynthetic pigments and suppressing photosynthesis in trees and other types of plants.Phaeophytinization is the process of converting chlorophylls into phaeophytins,for example by acidifi cation.Ozone is a highly oxidizing molecule and well known to degrade chlorophylls;however,the eff ect of ozone on phaeophytinization in leaves of higher plants is largely unknown.To reveal ozone eff ect on phaeophytinization and evaluate the potential of phaeophytinization as an index of ozone stress in trees,the absorbance at the optical density of 665 nm was measured before(OD_(665))and after(OD_(665a))acidifi cation in three independent experiments with nearly 30 conditions of ozone exposure.Both current ambient and elevated ozone widely aff ected phaeophytinization,as indicated by decreases or increases in the phaeophytinization quotient OD_(665)/OD_(665a).These eff ects were commonly moderate to large in magnitude and practically signifi cant,and occurred even in ozone-asymptomatic leaves.It emerges that the ozone eff ect on phaeophytinization is bimodal,likely depending on the intensity of ozone stress.These results indicate a promising feature of OD_(665)/OD_(665a)as a thorough index of ozone stress in the future,but further studies are needed to reveal the underlying biochemical mechanisms of the bimodal eff ect on phaeophytinization.

Single and combined eff ects of fertilization,ectomycorrhizal inoculation,and drought on container-grown Japanese larch seedlings

Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status.Therefore,it is important to enhance the tolerance to drought and thus health,vigor,and success of transplantation seedlings used in the forestry by modifying fertilization and promoting mycorrhization.Here,we sowed seeds of Japanese larch(Larix kaempferi)in 0.2-L containers with 0.5 g(low fertilization;LF)or 2 g(high fertilization;HF)of slow-release fertilizer early in the growing season.One month later,we irrigated seedlings with non-sterilized ectomycorrhizal inoculum(ECM)or sterilized solution(non-ECM),and after about 2 months,plants were either kept well watered(WW;500 mL water/plant/week)or subjected to drought(DR;50 mL water per plant/week)until the end of the growing season.HF largely stimulated plant growth and above-and belowground biomass production,eff ects that are of practical signifi cance,but caused a small decrease in stomatal conductance(Gs 390)and transpiration rate(E 390),which in practice is insignifi cant.ECM treatment resulted in moderate inhibition of seedling growth and biomass and largely canceled out the enhancement of biomass and foliar K content by HF.DR caused a large decrease in CO 2 assimilation,and enhanced stomatal closure and induced senescence.DR also largely depleted foliar Mg and enriched foliar K.Although DR caused a large decrease in foliar P content in LF,it moderately increased P in HF.Likewise,DR increased foliar K in HF but not in LF,and decreased foliar P in ECM plants but not in non-ECM plants.Conversely,ECM plants exhibited a large enrichment in foliar P under WW and had a lower water potential under DR when grown in LF.These results indicate that the drought tolerance and health and vigor of Japanese larch seedlings can be modifi ed by soil fertility and soil microorganisms.This study provides a basis for new multifactorial research programs aimed at producing seedlings of superior quality for forestation under climate change.

Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective

Root/shoot(R/S)ratio is an important index for assessing plant health,and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents.The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession,where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients.We present evidence showing the R/S ratio follows a biphasic dose–response relationship under stress,typical of hormesis.The R/S ratio in response to stress has been widely compared among species and ecological succession classes.It is constrained by a variety of factors such as ontogeny.Furthermore,the current literature lacks dose-response studies incorporating the full dose–response continuum,hence limiting scientific understanding and possible valuable application.The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations.Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions.

Ozone disrupts the communication between plants and insects in urban and suburban areas:an updated insight on plant volatiles

Plant-insect interactions are basic components of biodiversity conservation.To attain the international Sustainable Development Goals(SDGs),the interactions in urban and in suburban systems should be better understood to maintain the health of green infrastructure.The role of ground-level ozone(0_(3)) as an environmental stress disrupting interaction webs is presented.Ozone mixing ratios in suburbs are usually higher than in the center of cities and may reduce photosynthetic productivity at a relatively higher degree.Consequently,carbon-based defense capacities of plants may be suppressed by elevated 0_(3) more in the suburbs.However,contrary to this expectation,grazing damages by leaf beetles have been severe in some urban centers in comparison with the suburbs.To explain differences in grazing damages between urban areas and suburbs,the disruption of atmospheric communication signals by elevated 0_(3) via changes in plant-regulated biogenic volatile organic compounds and long-chain fatty acids are considered.The ecological roles of plant volatiles and the effects of 0_(3) from both a chemical and a biological perspective are presented.Ozone-disrupted plant volatiles should be considered to explain herbivory phenomena in urban and suburban systems.

Ethylenediurea(EDU)effects on hybrid larch saplings exposed to ambient or elevated ozone over three growing seasons

Ground-level ozone(O_(3))pollution is a persistent environmental issue that can lead to adverse effects on trees and wood production,thus indicating a need for forestry interventions to mediate O_(3) effects.We treated hybrid larch(Larix gmelinii var.japonica×L.kaempferi)saplings grown in nutrient-poor soils with 0 or 400 mg L^(-1) water solutions of the antiozonant ethylenediurea(EDU0,EDU400)and exposed them to ambient O_(3)(AOZ;08:00-18:00≈30 nmol mol^(-1)) or elevated O_(3)(EOZ;08:00-18:00≈60 nmol mol^(-1))over three growing seasons.We found that EDU400 protected saplings against most effects of EOZ,which included extensive visible foliar injury,premature senescence,decreased photosynthetic pigment contents and altered balance between pigments,suppressed gas exchange and biomass production,and impaired leaf litter decay.While EOZ had limited effects on plant growth(suppressed stem diameter),it decreased the total number of buds per plant,an effect that was not observed in the first growing season.These results indicate that responses to EOZ might have implications to plant competitiveness,in the long term,as a result of decreased potential for vegetative growth.However,when buds were standardized per unit of branches biomass,EOZ significantly increased the number of buds per unit of biomass,suggesting a potentially increased investment to bud development,in an effort to enhance growth potential and competitiveness in the next growing season.EDU400 minimized most of these effects of EOZ,significantly enhancing plant health under O_(3)-induced stress.The effect of EDU was attributed mainly to a biochemical mode of action.Therefore,hybrid larch,which is superior to its parents,can be significantly improved by EDU under long-term elevated O_(3) exposure,providing a perspective for enhancing afforestation practices.

thylenediurea(EDU)effects on Japanese larch:an one growing season experiment with simulated regenerating communities and a four growing season application to individual saplings

Japanese larch(Larix kaempferi(Lamb.)Carr.)and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere.Ground-level ozone(O_(3))concentrations have increased since the preindustrial era,and research projects showed that Japanese larch is susceptible to elevated O_(3)exposures.Therefore,methodologies are needed to(1)protect Japanese larch against O_(3)damage and(2)conduct biomonitoring of O_(3)in Japanese larch forests and,thus,monitor O_(3)risks to Japanese larch.For the first time,this study evaluates whether the synthetic chemical ethylenediurea(EDU)can protect Japanese larch against O_(3)damage,in two independent experiments.In the first experiment,seedling communities,simulating natural regeneration,were treated with EDU(0,100,200,and 400 mg L^(-1))and exposed to either ambient or elevated O_(3)in a growing season.In the second experiment,individually-grown saplings were treated with EDU(0,200 and 400 mg L-1)and exposed to ambient O_(3)in two growing seasons and to elevated O_(3)in the succeeding two growing seasons.The two experiments revealed that EDU concentrations of 200-400 mg L^(-1)could protect Japanese larch seedling communities and individual saplings against O_(3)-induced inhibition of growth and productivity.However,EDU concentrations≤200 mg L^(-1)did offer only partial protection when seedling communities were coping with higher level of O_(3)-induced stress,and only 400 mg EDU L^(-1)fully protected communities under higher stress.Therefore,we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O_(3)-induced stress is that of 400 mg EDU L^(-1).The results of this study can provide a valuable resource of information for applied forestry in an O_(3)-polluted world.

Ethylenediurea(EDU)spray effects on willows(Salix sachalinensis F.Schmid)grown in ambient or ozone-enriched air:implications for renewable biomass production

Ground-level ozone(O_(3)) is a widespread air pollutant causing extensive injuries in plants.However,its effects on perennial energy crops remain poorly under-stood due to technical difficulties in cultivating fast-growing shrubs for biomass production under O_(3) treatment on the field.Here we present the results of a two-year evaluation in the framework of which willow(Salix sachalinensis F.Schmid)shrubs were exposed to ambient(AOZ)or elevated(EOZ)O_(3) in two successive growing seasons(2014,2015)and treated with 0(EDU0)or 400 mg L^(−1)(EDU400)eth-ylenediurea spray in the second growing season.In 2014,EOZ altered the chemical composition of both top young and fallen leaves,and a novel mechanism of decreasing Mg in fallen leaves while highly enriching it in young top leaves was revealed in shrubs exposed to EOZ.In 2015,EDU400 alleviated EOZ-induced decreases in leaf fresh mass to dry mass ratio(FM/DM)and leaf mass per area(LMA).While EDU400 protected against EOZ-induced suppression of the maximum rate at which leaves can fix carbon(A_(max))in O_(3)-asymptomatic leaves,it did not alle-viate EOZ-induced suppression of the maximum rates of carboxylation(VCmax)and electron transport(J_(max))and chlorophylls a,b,and a+b in the same type of leaves.In O_(3)-symptomatic leaves,however,EDU400 alleviated EOZ-induced suppression of chlorophylls a and a+b,indicating different mode of action of EDU between O_(3)-asymptomatic and O_(3)-symptomatic leaves.Extensive herbivory occurred only in AOZ-exposed plants,leading to suppressed biomass production,while EOZ also led to a similar suppression of biomass production(EDU0×EOZ vs.EDU400×EOZ).In 2016,carry-over effects were also evaluated following cropping and transplantation into new ambient plots.Effects of EOZ in the preceding growing seasons extended to the third growing season in the form of suppressed ratoon biomass production,indicating carry-over effect of EOZ.Although EDU400 protected against EOZ-induced suppression of biomass production when applied in 2015,there was no carry-over effect of EDU in the absence of EDU treatment in 2016.The results of this study provide novel mechanistic understandings of O_(3)and EDU modes of action and can enlighten cultivation of willow as energy crop.

Elevated CO2 offsets the alteration of foliar chemicals(n-icosane,geranyl acetate,and elixene)induced by elevated O3 in three taxa of O3-tolerant eucalypts

Eucalypts are important forest resources in southwestern China,and may be tolerant to elevated ground-level ozone(O3)concentrations that can negatively affect plant growth.High CO2 may offset O3-induced effects by providing excess carbon to produce secondary metabolites or by inducing stomatal closure.Here,the effects of elevated CO2 and O3 on leaf secondary metabolites and other defense chemicals were studied by exposing seedlings of Eucalyptus globulus,E.grandis,and E.camaldulensis×E.deglupta to a factorial combination of two levels of O3(<10 nmol mol^(−1)and 60 nmol mol^(−1))and CO2(ambient:370μmol mol^(−1)and 600μmol mol^(−1))in open-top field chambers.GC-profiles of leaf extracts illustrated the effect of elevated O3 and the countering effect of high CO2 on compounds in leaf epicuticular wax and essential oils,i.e.,n-icosane,geranyl acetate and elixene,compounds known as a first-line defense against insect herbivores.n-Icosane may be involved in tolerance mechanisms of E.grandis and the hybrid,while geranyl acetate and elixene in the tolerance of E.globulus.Elevated O3 and CO2,singly or in combination,affected only leaf physiology but not biomass of various organs.Elevated CO2 impacted several leaf traits,including stomatal conductance,leaf mass per area,carbon,lignin,n-icosane,geranyl acetate and elixene.Limited effects of elevated O3 on leaf physiology(nitrogen,n-icosane,geranyl acetate,elixene)were commonly offset by elevated CO2.We conclude that E.globulus,E.grandis and the hybrid were tolerant to these O3 and CO2 treatments,and n-icosane,geranyl acetate and elixene may be major players in tolerance mechanisms of the tested species.

Effects of soil nutrient availability and ozone on container-grown Japanese larch seedlings and role of soil microbes

The interactive eff ects of ozone,soil nutrient availability and root microorganisms on physiological,growth,and productivity traits were studied for the fi rst time for Japanese larch(Larix kaempferi)seedlings grown in containers over a growing season,using a free air ozoneconcentration enrichment exposure system.High nutrient availability altered leaf and root nutrient dynamics and enhanced plant growth;however,it also enhanced seedling susceptibility to damping-off disease compared to low nutrient availability.Negative eff ects of elevated ozone,as compared with ambient ozone,on leaf gas exchange and plant stem form were neither off set nor exacerbated by soil nutrient availability and root colonizers.Such negative eff ects suggest that elevated ozone may have implications for ecological health even when plant vigor is limited by factors other than ozone.Inoculation of roots with ectomycorrhizae had negligible infl uence on the eff ects of either soil nutrient availability or ozone.However,this lack of eff ect may be upon impeded formation of complete mycorrhizal root tips due to factors other than the manipulated variables.B and Na appeared to have an important role in stress responses,so further studies to examine their link with physiological mechanisms as a function of time.This study provides an important perspective for designing forestry practices to enhance seedling health.

Emerging challenges of ozone impacts on asian plants:actions are needed to protect ecosystem health

Context:Ozone concentrations near the land surface are rising in Asia while they are declining or stagnating in Europe and North America.Ozone is the most widespread air pollutant negatively affecting vegetation,and its increased concentrations pose a major threat to food quality and production and other ecosystem services in Asia.Method:In this review,we provide an overview of scientific challenges in the impacts of ozone pollution on Asian vegetation,and synthesize the challenges toward mitigation of the impacts.Result:We argue that new policy initiatives need to seek both reduction of ozone levels and enhancement of plant tolerance to ozone to maintain food quality and ensure food supplies.Conclusion:The scientific advancements must be transferred to actions by two types of institutions:a)environmental agencies for reducing ozone levels and b)agricultural research institutions for enhancing plant tolerance to ozone.In connecting the scientific advancements with the institutional actions,scientists in Asian countries should play the key role taking advantages of interdisciplinary and international collaborations.