A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings...A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings and the allelopathy between the two tree species. Four concentrations （100 g. kg i, 50 g. kg^-1, 25 g. kg^-1 and 12.5 g. kg^-1） were prepared for each kind of extracts. Result showed that the water extracts with low and moderate concentrations accelerated the growth of collar diameter and increased biomass and root/shoot ratio of walnut seedlings. The water extracts from branches and barks with low and moderate concentrations accelerated the height growth of the seedlings, while those from leaves and roots slightly decreased the height growth of seedlings. The fact that application of water extracts of larch improved the growth of Manchurian walnut attributes possibly to the allelopathy between the two tree species.展开更多
A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk den...A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation management. Water deficit stress (Dstress) was quantified by the number of days when the water content in the surface 0.3 m deviated from the water content range determined by the Least Limiting Water Range (LLWR). Root and shoot samples were collected at the V6, V12, and R1 growth stages. There was no significant correlation between Dstress and shoot or root biomass at the V6 growth stage. At the V12 and R1 growth stages, there were negative, linear correlations among Dstress and both root biomass and shoot biomass. The proportional decrease of shoot biomass was greater than the proportional decrease in root biomass, leading to an increase in the root:shoot ratio as water deficit stress increased at all growth stages. Determining restrictive soil conditions using the LLWR may be useful for evaluating improvement or degradation of the soil physical environment caused by soil management.展开更多
[Objective] This study was to investigate the effect of atrazine stress on the growth of Pennisetum hydridum. [Method] Pot experiments were conducted to study the effects of atrazine stress （20, 50, 100, 200, 500 mg...[Objective] This study was to investigate the effect of atrazine stress on the growth of Pennisetum hydridum. [Method] Pot experiments were conducted to study the effects of atrazine stress （20, 50, 100, 200, 500 mg/kg） on plant height, biomass, root-shoot ratio and chlorophyll content of P. hydridum. [Results] Low level of atrazine stress （20 and 50 mg/kg） showed no significant effects on plant height and biomass of P. hydridum. Moderate level of atrazine stress （100 and 200 mg/kg） did not show significant effect on plant height, but did on the biomass of P. hydridum. Biomass of P. hydridum stressed by 100 and 200 mg/kg of atrazine was decreased by 34.1% and 36.4% compared with control, respectively. High level of atrazine stress （500 mg/kg） brought significant decrease in plant height（by 40.6%） and biomass（20.0%） of P. hydridum. All levels of atrazine stress showed no significant effects on root-shoot ratio and chlorophyll content of P. hydridum. [Conclusion] Pennisetum hydridum has strong tolerance to atrazine stress.展开更多
Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of gene...Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of general patterns in species allocation is still very limited.This is because each study was done in different condi-tions using different methodology,making generalization dif-ficult.We investigate intraspecific above-versus below-ground biomass allocation among individuals across a spectrum of dry-grassland plant species at two different developmental stages and ask whether allocation is age-and species specific,and whether differences among species can be explained by their life-history traits and phylogeny.Methods We collected data on above-and below-ground biomass of seedlings and adult plants of 20 species from a common garden experiment.We analysed data on shoot-root biomass allocation allometrically and studied the relationship between the allometric exponents(slopes on log-log scale),species life-history traits and phylogenetic distances.Important Findings We found isometric as well as allometric patterns of biomass alloca-tion in the studied species.Seedlings and adult individuals of more than half of the species differed in their above-versus below-ground biomass allometric exponents.Seedlings and adult individuals of the remaining species differed in their allometric coefficients(inter-cepts).Annual species generally allocated proportionally more to above-than below-ground biomass as seedlings than as adults,whereas perennial species showed the opposite pattern.Plant life-history traits,such as plant life span,age of first flowering,month in which the species begin flowering and specific leaf area were much more important in explaining differences in shoot-root allometry among species than were phylogenetic relationships.This suggests that allocation patterns vary greatly among closely related species but can be predicted based on species life-history traits.展开更多
The two cultivation patterns,no-tillage and ridge cultivation,are widely used in maize planting in Northeast China.However,the seed bounce in the falling process and drought seriously at the seedling stage often occur...The two cultivation patterns,no-tillage and ridge cultivation,are widely used in maize planting in Northeast China.However,the seed bounce in the falling process and drought seriously at the seedling stage often occur to affect the sowing quality,mean emergence time,percentage of emergence,root biomass,aboveground biomass and root shoot ratio of maize,and eventually reduces the grain yield.To solve the problems,a seed furrow liquid spraying device was designed and thereby the effects of spraying water volumes[0 L/m(V0),0.6 L/m(V1),1.2 L/m(V2)and 1.8 L/m(V3)]and nozzle types[conical nozzle(N1)and sectorial nozzle(N2)]on the sowing quality and seedling growth of maize were studied.The water volume and nozzle type had significant effects on the sowing quality(QR,CV,LD),not seedling growth(MET,PE,RB,AB,RSR)(p<0.05).Spraying water into seed furrow further humidified the soils around the maize seeds,effectively suppressing the bounce and rolling of seed and significantly promoting the growth and development of seeds.The sowing quality in the N2 treatment was significantly better than that in the N1 treatment.The qualified rate of seed spacing was increased with the increase of the water volume(V3>V2>V1>V0).However,the variability coefficient of seed spacing and lateral deviation of seed position were the opposite.The larger spraying water volume led to shorter mean emergence time(V0>V1>V2>V3)and higher percentage of emergence(V3>V2>V1>V0).The root biomass and aboveground biomass increased significantly with the enlargement of spraying water volume.Under different water volumes,the root shoot ratio differed significantly.The plants in the V1,V2 and V3 treatments had lower root shoot ratios compared with the V0 treatment.The increase of spraying water volume significantly reduced the root shoot ratio.The seed furrow liquid spraying device provides a reference for improving sowing quality and promoting seedling growth.展开更多
Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern US...Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern USA.Methods:One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content(RWC)and low cell sap osmotic potential(OP).Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies.These genotypes were also screened with 30%PEG8000.Root and shoot characteristics were studied in 10 genotypes.Results:The genotypes differed for RWC(33.7%–97.3%,mean:79.7%)and had an almost fivefold difference in OP(−0.5 to−2.4 MPa,mean:−1.2 MPa).Significant variation(p<0.001)for the main effects of environment and genotypes was found for RWC and OP.Apart from the greenhouse trial,no correlation was found between RWC and OP,indicating that differences in RWC might have been due to factors other than osmotic adjustment.Genotypes with either long roots or high root weights,and high root/shoot ratios demonstrated high RWC and low OP.Conclusions:Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.展开更多
Aims In the Core Cape Subregion(CCR),a Mediterranean-climate ecosystem with infertile soils,the legume species Podalyria calyptrata and P.burchellii are in a separate clade to P.leipoldtii and P.myrtillifolia.The clos...Aims In the Core Cape Subregion(CCR),a Mediterranean-climate ecosystem with infertile soils,the legume species Podalyria calyptrata and P.burchellii are in a separate clade to P.leipoldtii and P.myrtillifolia.The closely related species are allopatric,and with the west-east climate gradient and variation in soil nutrient availability in the CCR,it was hypothesized that the two closely related allopatric species would differ in their ecological niche and root:shoot ratio,specific root length(SRL)and organic acid exudation responses to phosphorus(P)supply.Methods With increasing P supply in the glasshouse,we measured plant biomass,leaf nitrogen([N]),[P],root morphology and release of organic acids.We determined species soil and leaf[N]and[P]and climate in field sites.Important FindingsAt low P supply,P.calyptrata roots exuded more organic acids than P.burchellii which instead produced roots with a greater SRL,and P.myrtillifolia allocated more biomass to roots than P.leipoldtii.In the field,leaf[P]and climate suggested that P.leipoldtii occupied the most oligotrophic niche followed by P.burchellii and then P.calyptrata and P.myrtillifolia.Closely related allopatric species differed in their mechanisms for P-acquisition and ecological niche,indicating that the environment overrides phylogeny in determining P-acquisition traits for these species,and suggesting that climate regulates nutrient availability,driving distribution and speciation.展开更多
Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shal...Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.展开更多
Precise estimation of vegetable nitrogen(N)status is critical in optimizing N fertilization management.However,nondestructive and accurate N diagnostic methods for vegetables are relatively scarce.In our two-year fiel...Precise estimation of vegetable nitrogen(N)status is critical in optimizing N fertilization management.However,nondestructive and accurate N diagnostic methods for vegetables are relatively scarce.In our two-year field experiment,we evaluated whether an active canopy sensor(GreenSeeker)could be used to nondestructively predict N status of bok choy(Brassica rapa subsp.chinensis)compared with a chlorophyll meter.Results showed that the normalized difference vegetation index(NDVI)and ratio vegetation index(RVI)generated by the active canopy sensor were well correlated with the aboveground biomass(AGB)(r=0.698–0.967),plant N uptake(PNU)(r=0.642–0.951),and root to shoot ratio(RTS)(r=-0.426 to-0.845).Compared with the chlorophyll meter,the active canopy sensor displayed much higher accuracy(5.0%–177.4%higher)in predicting AGB and PNU and equal or slightly worse(0.54–1.82 times that of the chlorophyll meter)for RTS.The sensor-based NDVI model performed equally well in estimating AGB(R2=0.63)and PNU(R2=0.61),but the meter-based model predicted RTS better(R2=0.50).Inclusion of the days after transplanting(DAT)significantly improved the accuracy of sensor-based AGB(19.0%–56.7%higher)and PNU(24.6%–84.6%higher)estimation models.These findings suggest that the active canopy sensor has a great potential for nondestructively estimating N status of bok choy accurately and thus for better N recommendations,especially with inclusion of DAT,and could be applied to more vegetables with some verification.展开更多
Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture wh...Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture when the possible effects of elevated CO2 concentration on trees are assessed. In this study, we grew Cinnamomum camphora seedlings under two CO2 concentrations （350 μmol/mol and 500μmnol/mol） and three soil moisture levels [80%, 60% and 40% FWC （field water capacity）] to focus on the effects of exposure of trees to elevated CO2 on underground and aboveground plant growth, and its dependence on soil moisture. The results indicated that high CO2 concentration has no significant effects on shoot height but significantly impacts shoot weight and ratio of shoot weight to height under three soil moisture levels. The response of root growth to CO2 enrichment is just reversed, there are obvious effects on root length growth, but no effects on root weight growth and ratio of root weight to length. The CO2 enrichment decreased 20.42%, 32.78%, 20.59% of weight ratio of root to shoot under 40%, 60% and 80% FWC soil water conditions, respectively. And elevated CO2 concentration significantly increased the water content in aboveground and underground parts. Then we concluded that high CO2 concentration favours more tree aboveground biomass growth than underground biomass growth under favorable soil water conditions. And CO2 enrichment enhanced lateral growth of shoot and vertical growth of root. The responses of plants to elevated CO2 depend on soil water availability, and plants may benefit more from CO2 enrichment with sufficient water supply.展开更多
基金This paper was supported by National Natural Science Foundation of China （No. 30400341） and Heilongjiang Provincial Science Foundation （No. C0320）Acknowledgement I thank Dr. YAN Xiu-feng for his help and guidance.
文摘A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings and the allelopathy between the two tree species. Four concentrations （100 g. kg i, 50 g. kg^-1, 25 g. kg^-1 and 12.5 g. kg^-1） were prepared for each kind of extracts. Result showed that the water extracts with low and moderate concentrations accelerated the growth of collar diameter and increased biomass and root/shoot ratio of walnut seedlings. The water extracts from branches and barks with low and moderate concentrations accelerated the height growth of the seedlings, while those from leaves and roots slightly decreased the height growth of seedlings. The fact that application of water extracts of larch improved the growth of Manchurian walnut attributes possibly to the allelopathy between the two tree species.
文摘A study was conducted at Akron, CO, USA, on a Weld silt loam in 2004 to quantify the effects of water deficit stress on corn (Zea mays, L.) root and shoot biomass. Corn plants were grown under a range of soil bulk density and water conditions caused by previous tillage, crop rotation, and irrigation management. Water deficit stress (Dstress) was quantified by the number of days when the water content in the surface 0.3 m deviated from the water content range determined by the Least Limiting Water Range (LLWR). Root and shoot samples were collected at the V6, V12, and R1 growth stages. There was no significant correlation between Dstress and shoot or root biomass at the V6 growth stage. At the V12 and R1 growth stages, there were negative, linear correlations among Dstress and both root biomass and shoot biomass. The proportional decrease of shoot biomass was greater than the proportional decrease in root biomass, leading to an increase in the root:shoot ratio as water deficit stress increased at all growth stages. Determining restrictive soil conditions using the LLWR may be useful for evaluating improvement or degradation of the soil physical environment caused by soil management.
基金Supported by Natural Science Foundation of Yunnan Province(2010CD058)~~
文摘[Objective] This study was to investigate the effect of atrazine stress on the growth of Pennisetum hydridum. [Method] Pot experiments were conducted to study the effects of atrazine stress （20, 50, 100, 200, 500 mg/kg） on plant height, biomass, root-shoot ratio and chlorophyll content of P. hydridum. [Results] Low level of atrazine stress （20 and 50 mg/kg） showed no significant effects on plant height and biomass of P. hydridum. Moderate level of atrazine stress （100 and 200 mg/kg） did not show significant effect on plant height, but did on the biomass of P. hydridum. Biomass of P. hydridum stressed by 100 and 200 mg/kg of atrazine was decreased by 34.1% and 36.4% compared with control, respectively. High level of atrazine stress （500 mg/kg） brought significant decrease in plant height（by 40.6%） and biomass（20.0%） of P. hydridum. All levels of atrazine stress showed no significant effects on root-shoot ratio and chlorophyll content of P. hydridum. [Conclusion] Pennisetum hydridum has strong tolerance to atrazine stress.
基金This study was supported by the Charles University in Prague,project GA UK No.658313.
文摘Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of general patterns in species allocation is still very limited.This is because each study was done in different condi-tions using different methodology,making generalization dif-ficult.We investigate intraspecific above-versus below-ground biomass allocation among individuals across a spectrum of dry-grassland plant species at two different developmental stages and ask whether allocation is age-and species specific,and whether differences among species can be explained by their life-history traits and phylogeny.Methods We collected data on above-and below-ground biomass of seedlings and adult plants of 20 species from a common garden experiment.We analysed data on shoot-root biomass allocation allometrically and studied the relationship between the allometric exponents(slopes on log-log scale),species life-history traits and phylogenetic distances.Important Findings We found isometric as well as allometric patterns of biomass alloca-tion in the studied species.Seedlings and adult individuals of more than half of the species differed in their above-versus below-ground biomass allometric exponents.Seedlings and adult individuals of the remaining species differed in their allometric coefficients(inter-cepts).Annual species generally allocated proportionally more to above-than below-ground biomass as seedlings than as adults,whereas perennial species showed the opposite pattern.Plant life-history traits,such as plant life span,age of first flowering,month in which the species begin flowering and specific leaf area were much more important in explaining differences in shoot-root allometry among species than were phylogenetic relationships.This suggests that allocation patterns vary greatly among closely related species but can be predicted based on species life-history traits.
基金We acknowledge that this work was financially supported by the 13th Five Year National Key R&D Plan Project(Grant No.:2017YFD0700701)the Development Programme of Science and Technology of Jilin Province of China(Grant No.20170312005ZX,20160441004SC).
文摘The two cultivation patterns,no-tillage and ridge cultivation,are widely used in maize planting in Northeast China.However,the seed bounce in the falling process and drought seriously at the seedling stage often occur to affect the sowing quality,mean emergence time,percentage of emergence,root biomass,aboveground biomass and root shoot ratio of maize,and eventually reduces the grain yield.To solve the problems,a seed furrow liquid spraying device was designed and thereby the effects of spraying water volumes[0 L/m(V0),0.6 L/m(V1),1.2 L/m(V2)and 1.8 L/m(V3)]and nozzle types[conical nozzle(N1)and sectorial nozzle(N2)]on the sowing quality and seedling growth of maize were studied.The water volume and nozzle type had significant effects on the sowing quality(QR,CV,LD),not seedling growth(MET,PE,RB,AB,RSR)(p<0.05).Spraying water into seed furrow further humidified the soils around the maize seeds,effectively suppressing the bounce and rolling of seed and significantly promoting the growth and development of seeds.The sowing quality in the N2 treatment was significantly better than that in the N1 treatment.The qualified rate of seed spacing was increased with the increase of the water volume(V3>V2>V1>V0).However,the variability coefficient of seed spacing and lateral deviation of seed position were the opposite.The larger spraying water volume led to shorter mean emergence time(V0>V1>V2>V3)and higher percentage of emergence(V3>V2>V1>V0).The root biomass and aboveground biomass increased significantly with the enlargement of spraying water volume.Under different water volumes,the root shoot ratio differed significantly.The plants in the V1,V2 and V3 treatments had lower root shoot ratios compared with the V0 treatment.The increase of spraying water volume significantly reduced the root shoot ratio.The seed furrow liquid spraying device provides a reference for improving sowing quality and promoting seedling growth.
文摘Background:Tall fescue(Festuca arundinacea Schreb.)is an important coolseason perennial grass.Its persistence and forage yield can be severely affected by drought stresses during the hot,dry summers of the southern USA.Methods:One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content(RWC)and low cell sap osmotic potential(OP).Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies.These genotypes were also screened with 30%PEG8000.Root and shoot characteristics were studied in 10 genotypes.Results:The genotypes differed for RWC(33.7%–97.3%,mean:79.7%)and had an almost fivefold difference in OP(−0.5 to−2.4 MPa,mean:−1.2 MPa).Significant variation(p<0.001)for the main effects of environment and genotypes was found for RWC and OP.Apart from the greenhouse trial,no correlation was found between RWC and OP,indicating that differences in RWC might have been due to factors other than osmotic adjustment.Genotypes with either long roots or high root weights,and high root/shoot ratios demonstrated high RWC and low OP.Conclusions:Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.
基金National Research Foundation(NRF),University of Cape Town and the Oppenheimer Memorial Trust.
文摘Aims In the Core Cape Subregion(CCR),a Mediterranean-climate ecosystem with infertile soils,the legume species Podalyria calyptrata and P.burchellii are in a separate clade to P.leipoldtii and P.myrtillifolia.The closely related species are allopatric,and with the west-east climate gradient and variation in soil nutrient availability in the CCR,it was hypothesized that the two closely related allopatric species would differ in their ecological niche and root:shoot ratio,specific root length(SRL)and organic acid exudation responses to phosphorus(P)supply.Methods With increasing P supply in the glasshouse,we measured plant biomass,leaf nitrogen([N]),[P],root morphology and release of organic acids.We determined species soil and leaf[N]and[P]and climate in field sites.Important FindingsAt low P supply,P.calyptrata roots exuded more organic acids than P.burchellii which instead produced roots with a greater SRL,and P.myrtillifolia allocated more biomass to roots than P.leipoldtii.In the field,leaf[P]and climate suggested that P.leipoldtii occupied the most oligotrophic niche followed by P.burchellii and then P.calyptrata and P.myrtillifolia.Closely related allopatric species differed in their mechanisms for P-acquisition and ecological niche,indicating that the environment overrides phylogeny in determining P-acquisition traits for these species,and suggesting that climate regulates nutrient availability,driving distribution and speciation.
基金sponsored by China Postdoctoral Science Foundation (Grant No.20090461149)the Postdoctoral Science Foundation of Jiangsu Province (Grant No. 0802029C)the Youth Science Foundation of JINAN Univeristy (Grant No. 51208026)
文摘Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.
基金supported by the National Key Research and Development Program of China(No.2016YFD0201001)the National Natural Science Foundation of China(No.31672236)
文摘Precise estimation of vegetable nitrogen(N)status is critical in optimizing N fertilization management.However,nondestructive and accurate N diagnostic methods for vegetables are relatively scarce.In our two-year field experiment,we evaluated whether an active canopy sensor(GreenSeeker)could be used to nondestructively predict N status of bok choy(Brassica rapa subsp.chinensis)compared with a chlorophyll meter.Results showed that the normalized difference vegetation index(NDVI)and ratio vegetation index(RVI)generated by the active canopy sensor were well correlated with the aboveground biomass(AGB)(r=0.698–0.967),plant N uptake(PNU)(r=0.642–0.951),and root to shoot ratio(RTS)(r=-0.426 to-0.845).Compared with the chlorophyll meter,the active canopy sensor displayed much higher accuracy(5.0%–177.4%higher)in predicting AGB and PNU and equal or slightly worse(0.54–1.82 times that of the chlorophyll meter)for RTS.The sensor-based NDVI model performed equally well in estimating AGB(R2=0.63)and PNU(R2=0.61),but the meter-based model predicted RTS better(R2=0.50).Inclusion of the days after transplanting(DAT)significantly improved the accuracy of sensor-based AGB(19.0%–56.7%higher)and PNU(24.6%–84.6%higher)estimation models.These findings suggest that the active canopy sensor has a great potential for nondestructively estimating N status of bok choy accurately and thus for better N recommendations,especially with inclusion of DAT,and could be applied to more vegetables with some verification.
基金Project supported by the National Natural Science Foundation of China (Nos. 30170161 and 90102015) and the Doctoral Disciplines Programs Foundation of Ministry of Education of China (No. 20030335043)
文摘Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture when the possible effects of elevated CO2 concentration on trees are assessed. In this study, we grew Cinnamomum camphora seedlings under two CO2 concentrations （350 μmol/mol and 500μmnol/mol） and three soil moisture levels [80%, 60% and 40% FWC （field water capacity）] to focus on the effects of exposure of trees to elevated CO2 on underground and aboveground plant growth, and its dependence on soil moisture. The results indicated that high CO2 concentration has no significant effects on shoot height but significantly impacts shoot weight and ratio of shoot weight to height under three soil moisture levels. The response of root growth to CO2 enrichment is just reversed, there are obvious effects on root length growth, but no effects on root weight growth and ratio of root weight to length. The CO2 enrichment decreased 20.42%, 32.78%, 20.59% of weight ratio of root to shoot under 40%, 60% and 80% FWC soil water conditions, respectively. And elevated CO2 concentration significantly increased the water content in aboveground and underground parts. Then we concluded that high CO2 concentration favours more tree aboveground biomass growth than underground biomass growth under favorable soil water conditions. And CO2 enrichment enhanced lateral growth of shoot and vertical growth of root. The responses of plants to elevated CO2 depend on soil water availability, and plants may benefit more from CO2 enrichment with sufficient water supply.
