Different responses of two Mosla species to potassium limitation in relation to acid rain deposition

Different responses of two Mosla species to potassium limitation in relation to acid rain deposition 1 first-author 1 1 1 1 2 1 corresp ‡Corresponding Author ‡Corresponding Author †E-mail:jchang@zju.edu.cn †E-mail:jchang@zju.edu.cn jchang@zju.edu.cn College of Life Sciences, Zhejiang University, Hangzhou 310058, China College of Life Sciences, Zhejiang University, Hangzhou 310058, China Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2E3, Canada The increasingly serious problem of acid rain is leading to increased potassium (K) loss from soils, and in our field investigation, we found that even congenerically relative Mosla species show different tolerance to K-deficiency. A hydroponic study was conducted on the growth of two Mosla species and their morphological, physiological and stoichiometric traits in response to limited (0.35 mmol K/L), normal (3.25 mmol K/L) and excessive (6.50 mmol K/L) K concentrations. Mosla hangchowensis is an endangered plant, whereas Mosla dianthera a widespread weed. In the case of M. hangchowensis , in comparison with normal K concentration, K-limitation induced a significant reduction in net photosynthetic rate ( P n ), soluble protein content, and superoxide dismutase (SOD) activity, but an increase in malondialdehyde (MDA) concentration. However, leaf mass ratio (LMR) and root mass ratio (RMR) were changed little by K-limitation. In contrast, for M. dianthera , K-limitation had little effect on P n , soluble protein content, SOD activity, and MDA concentration, but increased LMR and RMR. Critical values of N (nitrogen):K and K:P (phosphorus) ratios in the shoots indicated that limitation in acquiring K occurred under K-limited conditions for M. hangchowensis but not for M. dianthera . We found that low K content in natural habitats was a restrictive factor in the growth and distribution of M. hangchowensis , and soil K-deficiency caused by acid rain worsened the situation of M. hangchowensis , while M. dianthera could well acclimate to the increasing K-deficiency. We suggest that controlling the acid rain and applying K fertilizers may be an effective way to rescue the endangered M. hangchowensis . Ecophysiological response Endangered species Morphological plasticity Mosla species Weed INTRODUCTION 1 The increasingly serious problem of acid rain due to industrialization and anthropogenic activities has resulted in ecological concerns worldwide, especially in China during the past decades (Fig. 1 1 ) (Zhang et al., 2007 2007 ). The negatively charged nitrate and sulphate ions in acid rain may act as “counter-ions,” which allow cations such as potassium (K + ), sodium (Na + ), calcium (Ca 2+ ) and magnesium (Mg 2+ ) to be leached from the soil and become unavailable to plants (Ivring, 1983 1983 ). This will probably lead to nutrient deficiency. Potassium (K) is one of the most important metal elements influencing plant metabolism, growth and development (Marschner, 1995 1995 ; Jia et al., 2008 2008 ). Although the relationship between K supply and growth or physiological traits has been studied extensively in cultivated plants (Marschner, 1995 1995 ; Basile et al., 2003 2003 ), the relationship between K supply and growth, physiological or morphological traits in wild plants has received less attention (Chapin, 1980 1980 ; Marschner, 1995 1995 ). This is especially so for comparisons between endangered species and their weedy congeners. Mosla hangchowensis Matsuda (Lamiaceae), an endangered annual in China, has only five small (each is less than 4 m 2 ) local populations in the Yangtze River Delta region, where the acid rain problems are increasingly serious. Its habitats are limited to the top of rocky hills and/or roadsides beside gravel in higher mountainous regions (Chang et al., 1999 1999 ; Ge and Chang, 2001 2001 ). Its congeneric species, Mosla dianthera (Buch.-Ham.) Maxim, is widely distributed from northeast to southeast of Asia and in the center regions in China, and it is often a dominant species in the communities. Its habitats range from arid hills to the edge of wetlands and its distribution overlaps with that of M. hangchowensis (Fang et al., 1989 1989 ). In our previous analysis of 16 essential elements, we found that all but K concentrations in plant tissues of M. hangchowensis were within the normal ranges reported for most herbaceous species (Ge et al., 1997 1997 ). We also found that soil-available K content (0~20 cm deep soil) under M. hangchowensis communities was higher than that in similar habitats without M. hangchowensis , (101.3±5.3) and (60.1±13.8) mg K/kg soil, respectively ( P < 0.05), with the soil-available K measured by Flame Atomic Absorption Spectrometry with the extraction solution of NH 4 OAc according to Bao ( 2005 2005 ). However, the widespread M. dianthera that was distributed in similar habitat to that of M. hangchowensis had normal K concentrations in plant tissues. M. hangchowensis is more restricted to comparatively higher K habitats than M. dianthera , one presumption of which is that this species has low capacity to assimilate soil K, regardless of soil K content in the habitats. According to Tilman ( 1980 1980 ), the abilities of species in acquiring and using limiting nutrients determine their competitive success in the community. The reduced success of species with lower ability is especially obvious when the element content is low in their habitats. Therefore, it seems possible that M. hangchowensis is out-competed in habitats where the K content is low. The increasingly serious problem of acid rain in the Yangtze River Delta where the two Mosla species co-occur has a remarkable effect in reducing K content of habitats (Wang et al., 2003 2003 ; Mou and Zhu, 2005 2005 ), and thus has an ongoing influence on Mosla species. Here, we report a comparative study on the growth of M. hangchowensis and M. dianthera and their morphological, physiological and stoichiometrical responses to three levels of K supply representing limited, normal and excessive K availabilities. The particular objectives were (1) to compare the performance of the two species under the different K concentrations, (2) to establish whether M. hangchowensis has a lower ability to acquire K than M. dianthera , and (3) to predict the future population fates of the two congeneric species in face of soil K changes resulting from the increasingly serious problem of acid rain. MATERIALS AND METHODS 1 Plant materials 2 Seedlings of the two species were collected in April 2003 from two co-occurring natural populations on Wuchao Mountain (120°00′ E, 30°12′ N), which is located in Hangzhou, southeastern China. The seedlings were grown at Hangzhou Botanical Garden (120°16′ E, 30°15′ N) under natural conditions until seeds could be harvested, and were then air-dried and stored in a refrigerator (4 °C) (SC-329GA, Haier Group, China) in November 2003. Seeds were germinated in early May 2004 in trays of peat (Sunshine Mix 6, Sun Gro Horticulture Canada Ltd.) and maintained in growth chambers with a 16-h photoperiod, day/night temperatures of 25/15 °C, relative humidity of 70%~80%, and irradiance ( λ =400~700 nm) of approximately 250 μmol photon/(m 2 ·s). When the height of plants reached about 4 cm, the seedlings were transplanted to plastic containers (39 cm×29 cm×12 cm), which were filled with different concentrations of Knop’s solution and continuously aerated by air pumps (Farr, 1925 1925 ). Plants were grown for 10 weeks in a greenhouse in the College of Life Science, Zhejiang University, Hangzhou (120°05′ E, 30°18′ N) with 70% full ambient irradiance. The average daily temperature ranged from 20 to 36 °C during the experiment, which lasted from early May to mid July 2004. Experimental design 2 The experiment used a 2×3×6 randomized complete block design (RCBD) with a total of 432 plants (432=2 species×3 K concentrations×6 blocks× 12 plants per box within each block). Twelve seedlings of each species were randomly selected and planted (supported by a foam plug) in each container, with one seedling in each grid cell. The foam plug provided room for stem expansion as the plant grew. Evaporation of water from the container was prevented by airproofing the foam plug with lanolin. The three K concentrations were: (1) control, referred to as the K3 treatment, continuously received normal Knop’s nutrient solution containing 3.25 mmol K/L, representing K concentrations in the soil solution under normal field conditions; (2) the K-limiting treatment, referred to as the K0 treatment, continuously received normal Knop’s nutrient solution containing 0.35 mmol K/L, representing K concentrations under field conditions for soils with low K availability (Nisbet and Shaw, 1996 1996 ; Reisenauer, 1966 1966 ); and (3) the excess K treatment, referred to as the K6 treatment, received the nutrient solution containing 6.50 mmol K/L, reflecting K concentrations in soils with high K availability due to dry K deposition (Luo et al., 2006 2006 ). A combination of KCl, NaH 2 PO 4 , and NaNO 3 was utilized to maintain equal K + , Na + and NO 3 − concentrations. The solutions were renewed once a week. Measurements and calculation 2 Measurements were conducted in mid July when the species were growing vigorously. Crown dimension (defined as the product of crown width measured in two perpendicular directions) and above ground height of the plants were measured. Six out of the 12 plants in each container were selected randomly. The rate of net photosynthesis rate ( P n ) was measured between 09:00 and 11:00 a.m. using a portable gas exchange system (Model LCA-4, ADC Ltd., Hoddesdon, UK), and the CO 2 concentration and temperature in the leaf chamber were maintained at 360 μmol CO 2 /mol and 25 °C, respectively. The extraction of soluble protein was carried out according to Jordan et al.( 1992 1992 ) and determined with Folin-Ciocalteu reagent according to Lowry et al.( 1951 1951 ). The activity of superoxide dismutase (SOD) was assayed by measuring its ability to inhibit the photochemical reduction of nitro blue tetrazolium (NBT) (Beauchamp and Fridovich, 1971 1971 ). Malondialdehyde (MDA) concentration was measured by the thiobarbituric acid reaction (Stewart and Bewley, 1980 1980 ). After these measurements the plants were harvested and separated into leaves, stems and roots. All samples were then dried in an oven at 80 °C for at least 48 h to constant weight. Height ratio (HR, height per unit biomass), leaf mass ratio (LMR, leaf mass/total mass) and root mass ratio (RMR, root mass/total mass) were calculated according to Hunt ( 1978 1978 ) and Sakai ( 1995 1995 ). Stem mass ratio (SMR, stem mass/total mass) was not examined, since only two of the three allocation traits (LMR, SMR and RMR) were independent variables. The plant samples were then ground and analyzed for N concentration using Nessler’s reagent (Yuen and Pollard, 1952 1952 ) after the samples were digested with H 2 SO 4 /H 2 O 2 (Bao, 2005 2005 ). The analyses of K and P concentrations in the digests were conducted using a Thermo Electron Corp. IRIS Intrepid II Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) (Waltham, MA, USA). Nutrient concentrations are reported for the dry weights of leaf, shoot (leaves plus stems), and whole plant bases. Statistical analysis 2 Statistical analysis was conducted using SPSS 15.0 for Windows (SPSS Inc., Chicago, Illinois, USA). Normality of the dataset was tested by the Shapiro-Wilks test and the result showed that data transformations were not required. The Levene’s test conducted using the general linear model (GLM) procedure showed that the data had homogeneous variances. Since there was no significant species×K treatment interaction, the treatment effects on biomass production, crown dimension, height, and HR and the differences between species were tested using a two-way analysis of variance (ANOVA) followed by least significant difference (LSD) test to compare the main effect in GLM univariate procedure. The effects of species, K treatments and their interaction on LMR, RMR, P n , soluble protein concentration, MDA concentration, SOD activity, and tissue K, N and P concentrations were tested by general linear mixed model in SPSS, with species and K treatments as fixed factors. All data are presented as mean±standard error (SE), and statistical significance was determined at P < 0.05. RESULTS 1 Growth and morphological response to different K treatments 2 There were no significant differences between K3 and K6 in the four traits of either species ( P > 0.05, Fig. 2 2 ; ANOVA data are shown in Table 1 1 , same below). Biomass production and crown dimension were significantly higher, while HR was lower across the K treatments for M. hangchowensis than for M. dianthera ( P < 0.05). Across the two species, biomass production, crown dimension and height were significantly lower under K0 than under K3 ( P < 0.05). Error bars are standard errors. Different letters in each graph indicate significant differences ( P < 0.05) between species or among K treatments HR: height ratio; LMR: leaf biomass ratio; RMR: root biomass ratio; P n : net photosynthesis ratio; MDA: malondialdehyde; SOD: superoxide dismutase. The P values less than 0.05 are highlighted 2 2 Parameters 2 Species 2 K treatment 2 Species×K F value P value F value P value F value P value 2 Biomass production 16.71 0.001 4.28 0.037 1.84 0.198 2 Crown dimension 10.34 0.007 6.54 0.011 0.60 0.564 2 Height 2.99 0.108 6.39 0.012 2.52 0.119 2 HR 7.39 0.018 0.48 0.630 0.95 0.412 2 LMR 26.35 <0.001 31.82 <0.001 8.56 0.004 2 RMR 0.11 0.750 8.86 0.004 41.17 <0.001 2 P n 1.49 0.232 25.25 <0.001 5.74 0.008 2 Soluble protein concentration 200.16 <0.001 4.48 0.026 39.56 <0.001 2 MDA concentration 4.76 0.037 4.04 0.028 1.24 0.030 2 SOD activity 37.19 <0.001 3.44 0.046 11.48 <0.001 K concentration Leaf 1.73 0.236 1747.79 <0.001 106.70 <0.001 Shoot 9.20 0.023 139.57 <0.001 6.94 0.028 Plant 28.02 0.002 375.26 <0.001 14.99 0.005 N concentration Leaf 9.54 0.021 17.61 0.003 23.26 0.001 Shoot 0.12 0.743 1.45 0.307 27.09 0.001 Plant 2.31 0.179 13.68 0.006 141.02 <0.001 P concentration Leaf 0.41 0.544 1.29 0.341 2.92 0.130 Shoot 9.27 0.023 1.22 0.361 2.06 0.209 Plant 2.10 0.198 9.44 0.014 7.19 0.026 For M. hangchowensis , neither K0 nor K6 affected LMR in comparison with K3 ( P > 0.05, Fig. 3 3 ). However, for M. dianthera , LMR was significantly higher under K0 than under K3 ( P < 0.05). Under K3 and K6, LMR of M. hangchowensis was significantly higher than that of M. dianthera ( P < 0.05). RMR did not change with increasing K supply for M. hangchowensis ( P > 0.05, Fig. 3 3 ); while it was higher under K0 than under K3 for M. dianthera ( P < 0.05). Under K0, RMR of M. hangchowensis was significantly lower than that of M. dianthera ( P < 0.05). Error bars are standard errors. Different letters in each graph indicate significant differences ( P < 0.05) among K treatments for the same species; * indicates significant difference ( P < 0.05) between species under the same K treatment Response of physiological parameters to different K treatments 2 There was no significant difference between K3 and K6 in any of the four physiological traits for either species ( P > 0.05, Fig. 4 4 ). For M. hangchowensis , P n , soluble protein content and SOD activity were lower while MDA content was higher under K0 than under K3 ( P < 0.05). However, for M. dianthera , no differences were evident between K0 and K3 for the four traits measured ( P > 0.05). Under K0 and K3, soluble protein content of M. hangchowensis was higher than that of M. dianthera ( P < 0.05). Under the same K treatment, the SOD activity of M. hangchowensis was lower than that of M. dianthera ( P < 0.05). Error bars are standard errors. Different letters in each graph indicate significant differences ( P < 0.05) among K treatments for the same species; * indicates significant difference ( P < 0.05) between species under the same K treatment Response of stoichiometrical traits to different K treatments 2 For M. hangchowensis , K concentrations in the leaf, shoot (leaves plus stem) and whole plant increased with K supply ( P < 0.05, Table 2 2 ), while for M. dianthera , only leaf K concentration was higher under K6 than under K3 ( P < 0.05). K concentrations in the leaf, shoot and whole plant were all lower in M. hangchowensis than in M. dianthera under K0 ( P < 0.05), while leaf K concentration was higher in M. hangchowensis than in M. dianthera under K3 ( P < 0.05). K0: 0.35 mmol K/L; K3: 3.25 mmol K/L; K6: 6.50 mmol K/L. All data are expressed as mean± SE . Different lowercase letters following the values in each column indicate significant differences ( P < 0.05) among K treatments for the same species and no letter means no significant inter-treatment difference. DW=dry weight indicates significant difference ( P < 0.05) between species under the same K treatment 2 3 K concentration (g/kg DW) 3 N concentration (g/kg DW) 3 P concentration (g/kg DW) Leaf Shoot Plant Leaf Shoot Plant Leaf Shoot Plant 10 M. hangchowensis K0 7.35±0.68c 6.07±0.56c 6.60±1.14b 17.05±2.55b 9.70±1.37b 12.36±1.78a 2.17±0.74 1.92±0.66 3.21±0.30a K3 30.66±0.44b 22.94±1.30b 24.02±2.41a 20.96±1.52b 8.53±0.64b 9.25±0.94b 2.23±0.81 1.98±0.44 2.69±0.19ab K6 38.79±3.90a 30.43±2.51a 24.79±3.65a 31.18±2.16a 14.10±0.73a 12.19±1.02a 2.31±0.64 1.95±0.55 2.37±0.27b 10 M. dianthera K0 29.85±2.32a * * 28.70±2.19 * * 26.21±2.96 * * 21.79±2.70b 10.59±1.09b 10.87±1.30b 2.69±0.35 2.50±0.33 3.24±0.41a K3 26.08±2.28b * * 26.13±4.75 22.63±4.83 36.71±0.42a * * 14.60±0.37a * * 13.03±0.43a * * 2.30±0.07 2.02±0.09 1.85±0.09b * * K6 33.12±1.68a 31.39±2.84 27.20±2.85 23.62±2.17b * * 7.85±0.64c * * 6.94±0.67c * * 1.99±1.14 2.36±0.95 2.09±0.96a For M. hangchowensis , N concentrations in the leaf, shoot and whole plant were all higher under K6 than under K3 ( P < 0.05, Table 2 2 ). N concentration in the whole plant was higher under K0 than under K3 ( P < 0.05). For M. dianthera , N concentrations in the leaf, shoot and whole plant were all lower under K0 and K6 than under K3 ( P < 0.05). N concentrations of the leaf, shoot and whole plant were all lower in M. hangchowensis than in M. dianthera under K3, while higher under K6 ( P < 0.05). P concentration in whole plant was unaffected by K0 and K6 in comparison with K3 for M. hangchowensis ( P > 0.05), while it was higher under K0 and K6 than under K3 for M. dianthera ( P < 0.05, Table 2 2 ). Under K3, P concentration in the whole plant of M. hangchowensis was higher than that of M. dianthera ( P < 0.05). DISCUSSION 1 Induced variation in stoichiometrical traits by different tissue K concentrations 2 Critical values for assessing nutrient limitation have been developed for different plant species (Marschner, 1995 1995 ; Koerselman and Meuleman, 1996 1996 ; Aerts and Chapin, 2000 2000 ). According to the often-used critical values for general plants, tissue K concentration of 8 g/kg is considered the lowest amount for plant growth (Marschner, 1995 1995 ). We found that tissue K concentration of M. hangchowensis under limited K supply was below the critical value, 8 g K/kg dry weight (DW) (Table 2 2 and Fig. 5 5 ). However, for M. dianthera , tissue K concentrations were all higher than 20 g/kg DW under K-limited condition (Table 2 2 and Fig. 5 5 ). It suggests that two species have different K uptake ability when K supply is limited. While under normal and excessive K conditions, tissue K concentrations in both species were all within the normal range found by Marschner ( 1995 1995 ) for many plant species (Table 2 2 ). Dotted lines represent critical tissue nutrient concentrations, 8 g/kg DW for K, 20 g/kg DW for N, and 1 g/kg DW for P (Aerts and Chapin, 2000 2000 ). DW: dry weight. The solid line indicates the critical nutrient ratio (N:K=2.1:1, K:P=3.4:1) To further assess the limitation that occurred in M. hangchowensis under K-limited condition, we evaluated tissue N:K and K:P ratios. Olde Venterink et al.( 2003 2003 ) proposed that if shoot (leaves plus stem) N:K ratio > 2.1 and K:P ratio < 3.4, then K-limitation is implied. In current study, for M. hangchowensis , N:K was higher than 2.1 and K:P was lower than 3.4, showing that K-limitation was induced in M. hangchowensis under K-limited condition (Fig. 5 5 ). However, for M. dianthera , the higher K concentration in the shoot and the normal critical N:K and K:P ratios both indicate its tolerance to low K, and no K-limitation was implied. Physiological response to variation in K concentrations 2 The basic roles that K plays in plants are to promote osmotic adjustment, photosynthesis and protein synthesis (Ashraf and Naz, 1994 1994 ; Quintero et al., 1998 1998 ). We found that P n and K concentrations in the leaf of M. hangchowensis , but not M. dianthera , were significantly reduced by low K (Fig. 4 4 and Table 2 2 ). In contrast, P n was not affected by the limited K supply for M. dianthera , suggesting that the two species had different physiological response patterns to K supply. The lack of K-limitation effect on P n in M. dianthera might be due to its efficient K uptake mechanism because its tissue K concentrations were little affected by the K-limitation and remained normal under K-limited condition (Table 2 2 ). Soluble protein plays an important role in reducing damage to plants under environmental stress (Öncel et al., 2004 2004 ). SOD reduces damage to the electron transfer system (Halliwell, 1987 1987 ) and restrains the formation of free radicals to activate the antioxidant defense mechanism, which protects the unsaturated membrane lipids, nucleic acids, enzymes and other cellular structures from the harmful effects of free radicals (Larson, 1988 1988 ; Foyer et al., 1994 1994 ). MDA is a secondary end product of the oxidation of polyunsaturated fatty acids and its amount may reflect general lipid peroxidation (Stewart and Bewley, 1980 1980 ). In the current study, K-limitation reduced the soluble protein content and SOD activity, and increased the MDA concentration of M. hangchowensis , which indicates that lipid peroxidation was enhanced, while the activity of defense enzymes was reduced. Hence, M. hangchowensis was probably injured by K-limitation. In contrast, M. dianthera showed well adaptation to both K-limitation and K-excess and maintained a well-regulated metabolism, which indicates good tolerance to a wide ecological range of K supplies. Growth and morphological response to different K treatments 2 High biomass allocation to the root may be beneficial to nutrient and water uptake while high HR is often regarded as a light-seeking strategy for species under dense canopies (Sakai, 1995 1995 ; Pothier and Prévost, 2002 2002 ). In addition, high LMR is an advantage to maintain high P n for supplying energy for K uptake. We found that M. hangchowensis did not adjust its morphological traits to alleviate the adverse effects caused by K-limitation (Fig. 3 3 ). In contrast, M. dianthera increased LMR and RMR to keep K-uptake capacity as well as photosynthetic capacity relatively unaffected. This seems to be a competitive strategy for M. dianthera under K-limitation condition. Actuality and prospect of two Mosla species in response to environmental changes 2 Species with lower element utilization ability will be defeated in competition in environments with low element availability (Tilman, 1980 1980 ). The lack of ability of M. hangchowensis to acclimate well to K-limited condition might lead to a decrease in population in the community and probably aggravates its endangerment. In contrast, M. dianthera can acclimate well to a broad range of K concentrations and the wide ecological adaptation for K resources may have helped M. dianthera distribute widely in the subtropical and tropical zones of China and in other countries of East and Southeast Asia (Fang et al., 1989 1989 ). It therefore seems probable that the low K content in natural habitats is a restrictive factor in the growth and distribution of M. hangchowensis and the decline of K supply in relation to acid rain will worsen the situation of M. hangchowensis , while M. dianthera can well acclimate to the increasing K-deficiency. This idea needs to be further tested in the field, and if established, controlling the acid rain and applying K fertilizers may be an effective way to relieve the increasingly serious problem of endangerment of M. hangchowensis . References R Aerts , FS Chapin . The mineral nutrition of wild plants revisited: a re-evaluation of processes and patterns . Adv Ecol Res , 2000 . 30 1 - 67 . DOI: 10.1016/S0065-2504(08)60016-1 http://doi.org/10.1016/S0065-2504(08)60016-1 . The mineral nutrition of wild plants revisited: a re-evaluation of processes and patterns M Ashraf , F Naz . Responses of some arid zone grasses to K-deficiency . Acta Physiol Plant , 1994 . 16 69 - 80 . . Responses of some arid zone grasses to K-deficiency SD Bao . Soil and Agricultural Chemistry Analysis , 2005 . : Beijing, China China Agriculture Press , 106 - 268 . (in Chinese) . Soil and Agricultural Chemistry Analysis B Basile , EJ Reidel , SA Weinbaum , TM DeJong . Leaf potassium concentration, CO 2 exchange and light interception in almond trees ( Prunus dulcis (Mill) D.A. Webb) . Sci Hortic-AMSTERDAM , 2003 . 98 ( 2 ): 185 - 194 . DOI: 10.1016/S0304-4238(02)00214-5 http://doi.org/10.1016/S0304-4238(02)00214-5 . Leaf potassium concentration, CO2 exchange and light interception in almond trees (Prunus dulcis (Mill) D.A. Webb) C Beauchamp , I Fridovich . Superoxide dismutase: improved assays and an assay applicable to acrylamide gels . Anal Biochem , 1971 . 44 ( 1 ): 276 - 287 . 4943714 DOI: 10.1016/0003-2697(71)90370-8 http://doi.org/10.1016/0003-2697(71)90370-8 . Superoxide dismutase: improved assays and an assay applicable to acrylamide gels J Chang , K Liu , Y Ge , GQ Qin . Features of the photosynthesis of Mosla hangchowensis and the response of photosynthesis to soil water status . Acta Phytoecol Sin , 1999 . 23 62 - 70 . (in Chinese) . Features of the photosynthesis of Mosla hangchowensis and the response of photosynthesis to soil water status FSIII Chapin . The mineral nutrition of wild plants . Annu Rev Ecol Syst , 1980 . 11 233 - 260 . DOI: 10.1146/annurev.es.11.110180.001313 http://doi.org/10.1146/annurev.es.11.110180.001313 . The mineral nutrition of wild plants YY Fang , JX Wang , Z Wei , 等 . Flora of Zhejiang (V) , 1989 . : Hangzhou, China Science and Technology Publishing House , 289 - 290 . (in Chinese) . Flora of Zhejiang (V) CH Farr . Root-hair elongation in Knop’s solution and in tap water . Am J Bot , 1925 . 12 ( 7 ): 372 - 383 . DOI: 10.2307/2435496 http://doi.org/10.2307/2435496 . Root-hair elongation in Knop’s solution and in tap water CH Foyer , M Lelandais , KJ Kunert . Photooxidative stress in plants . Physiol Plant , 1994 . 92 ( 4 ): 696 - 717 . DOI: 10.1111/j.1399-3054.1994.tb03042.x http://doi.org/10.1111/j.1399-3054.1994.tb03042.x . Photooxidative stress in plants Y Ge , J Chang . Existence analysis of populations of Molsa hangchowensis , an endangered plant . Bot Bul Acad Sin , 2001 . 42 141 - 147 . . Existence analysis of populations of Molsa hangchowensis, an endangered plant Y Ge , J Chang , GQ Qin , 等 . LJ Yan , YX Bao , JD Qian . The Correlation of Element Uptake in Mosla Hangchowensis . Research on and Probe into Ecology , 1997 . : Beijing, China China Environmental Science , 137 - 141 . (in Chinese) . The Correlation of Element Uptake in Mosla Hangchowensis B Halliwell . Oxidative damage, lipid peroxidation and antioxidant protection in chloroplasts . Chem Phys Lipids , 1987 . 44 ( 2-4 ): 327 - 340 . DOI: 10.1016/0009-3084(87)90056-9 http://doi.org/10.1016/0009-3084(87)90056-9 . Oxidative damage, lipid peroxidation and antioxidant protection in chloroplasts R Hunt . Plant Growth Analysis , 1978 . : London, UK Edward Arnold , . Plant Growth Analysis PM Ivring . Acidic precipitation effects on crops: a review and analysis of research . J Environ Qual , 1983 . 12 442 - 453 . . Acidic precipitation effects on crops: a review and analysis of research YB Jia , XE Yang , Y Feng , G Jilani . Differential response of root morphology to potassium deficient stress among rice genotypes varying in potassium efficiency . J Zhejiang Univ Sci B , 2008 . 9 ( 5 ): 427 - 434 . 18500783 DOI: 10.1631/jzus.B0710636 http://doi.org/10.1631/jzus.B0710636 . Differential response of root morphology to potassium deficient stress among rice genotypes varying in potassium efficiency BR Jordan , J He , WS Chow , JM Anderson . Changes in mRNA levels and polypeptide subunits of ribulose-1,5-bisphosphate carboxylase in response to supplementary ultraviolet-B radiation . Plant Cell Environ , 1992 . 15 ( 1 ): 91 - 98 . DOI: 10.1111/j.1365-3040.1992.tb01461.x http://doi.org/10.1111/j.1365-3040.1992.tb01461.x . Changes in mRNA levels and polypeptide subunits of ribulose-1,5-bisphosphate carboxylase in response to supplementary ultraviolet-B radiation W Koerselman , AM Meuleman . The vegetation N:P ratio: a new tool to detect the nature of nutrient limitation . J Appl Ecol , 1996 . 33 ( 6 ): 1441 - 1450 . DOI: 10.2307/2404783 http://doi.org/10.2307/2404783 . The vegetation N:P ratio: a new tool to detect the nature of nutrient limitation RA Larson . The antioxidants of higher plants . Phytochemistry , 1988 . 27 ( 4 ): 969 - 978 . DOI: 10.1016/0031-9422(88)80254-1 http://doi.org/10.1016/0031-9422(88)80254-1 . The antioxidants of higher plants OH Lowry , NJ Rosebrough , AL Farr , RJ Randal . Protein measurement with the Folin phenol reagent . J Biol Chem , 1951 . 193 265 - 275 . 14907713 . Protein measurement with the Folin phenol reagent YH Luo , TG Dai , K Liang . Study on distribution of the atmospheric dust fall and its metal element contents in shaoguan city, Guangdong province . Geol Surv Res , 2006 . 29 ( 1 ): 64 - 68 . (in Chinese) . Study on distribution of the atmospheric dust fall and its metal element contents in shaoguan city, Guangdong province H Marschner . Mineral Nutrition of Higher Plants , 1995 . : San Diego, USA Academic Press , . Mineral Nutrition of Higher Plants MEP (Ministry of Environmental Protection of the People’s Republic of China) Report on the State of the Environment in China 2006 , 2007 . Available from: http://english.mep.gov.cn/standards_reports/soe/SOE2006/200711/t20071105_112565.htm http://english.mep.gov.cn/standards_reports/soe/SOE2006/200711/t20071105_112565.htm [Accessed 08/02/2009] . Report on the State of the Environment in China 2006 YM Mou , GL Zhu . The study of acid rain distribution of Zhejiang Province based on GIS . Bul Sci Tech , 2005 . 21 ( 3 ): 356 - 359 . (in Chinese) . The study of acid rain distribution of Zhejiang Province based on GIS AF Nisbet , S Shaw . Dynamics of Radionuclide Behaviour in Soil Solution: Compilation of Data from Lysimeter and Field Studies . Technical Report, NRPB-M674 , 1996 . : Chilton, UK National Radiological Protection Board , . Dynamics of Radionuclide Behaviour in Soil Solution: Compilation of Data from Lysimeter and Field Studies H Olde Venterink , MJ Wassen , A Verkroost , PC Ruiter . Species richness-productivity patterns differ between N-, P- and K-limited wetlands . Ecology , 2003 . 84 ( 8 ): 2191 - 2199 . DOI: 10.1890/01-0639 http://doi.org/10.1890/01-0639 . Species richness-productivity patterns differ between N-, P- and K-limited wetlands I Öncel , E Yurdakulol , Y Keleş , L Kurt , A Yıldız . Role of antioxidant defense system and biochemical adaptation on stress tolerance of high mountain and steppe plants . Acta Oecol-Int J Ecol , 2004 . 26 ( 3 ): 211 - 218 . DOI: 10.1016/j.actao.2004.04.004 http://doi.org/10.1016/j.actao.2004.04.004 . Role of antioxidant defense system and biochemical adaptation on stress tolerance of high mountain and steppe plants D Pothier , M Prévost . Photosynthetic light response and growth analysis of competitive regeneration after partial cutting in a boreal mixed stand . Trees-Structure and Function , 2002 . 16 ( 4-5 ): 365 - 373 . DOI: 10.1007/s00468-001-0158-y http://doi.org/10.1007/s00468-001-0158-y . Photosynthetic light response and growth analysis of competitive regeneration after partial cutting in a boreal mixed stand JM Quintero , JM Fournier , J Ramos , M Benlloch . K + status and ABA affect both exudation rate and hydraulic conductivity in sunflower roots . Physiol Plant , 1998 . 102 ( 2 ): 279 - 284 . DOI: 10.1034/j.1399-3054.1998.1020216.x http://doi.org/10.1034/j.1399-3054.1998.1020216.x . K+ status and ABA affect both exudation rate and hydraulic conductivity in sunflower roots HM Reisenauer . PL Altman , DS Dittmer . Mineral Nutrients in Soil Solution . Environmental Biology , 1966 . : Bethesda Federation of American Societies for Experimental Biology , 507 - 508 . . Mineral Nutrients in Soil Solution S Sakai . Evolutionarily stable growth of a sapling which waits for future gap formation under closed canopy . Evol Ecol , 1995 . 9 ( 4 ): 444 - 452 . DOI: 10.1007/BF01237766 http://doi.org/10.1007/BF01237766 . Evolutionarily stable growth of a sapling which waits for future gap formation under closed canopy RC Stewart , JD Bewley . Lipid peroxidation associated with accelerated aging of soybean axes . Plant Physiol , 1980 . 65 ( 2 ): 245 - 248 . 16661168 DOI: 10.1104/pp.65.2.245 http://doi.org/10.1104/pp.65.2.245 . Lipid peroxidation associated with accelerated aging of soybean axes D Tilman . Resources: A Graphical-Mechanistic Approach to Competition and predation . Am Nat , 1980 . 116 ( 3 ): 362 - 393 . DOI: 10.1086/283633 http://doi.org/10.1086/283633 . Resources: A Graphical-Mechanistic Approach to Competition and predation DZ Wang , X Jiang , YR Bian , YH Lang , F Wang , JZ He . K + adsorption characteristics and reaction kinetics in red soft under acid deposition . China Environ Sci , 2003 . 23 ( 2 ): 171 - 175 . (in Chinese) . K+ adsorption characteristics and reaction kinetics in red soft under acid deposition SH Yuen , AG Pollard . The determination of nitrogen in agricultural materials by the Nessler reagent: preparation of the reagent . J Sci Food Agric , 1952 . 3 ( 10 ): 441 - 447 . DOI: 10.1002/jsfa.2740031002 http://doi.org/10.1002/jsfa.2740031002 . The determination of nitrogen in agricultural materials by the Nessler reagent: preparation of the reagent JE Zhang , Y Ouyang , DJ Ling . Impacts of simulated acid rain on cation leaching from the Latosol in south China . Chemosphere , 2007 . 67 ( 11 ): 2131 - 2137 . 17307220 DOI: 10.1016/j.chemosphere.2006.12.095 http://doi.org/10.1016/j.chemosphere.2006.12.095 . Impacts of simulated acid rain on cation leaching from the Latosol in south China We thank Dr. Barry Madison and Dr. Ashton Duvall of Queen’s University, Canada for their help on the language on an earlier version of this manuscript. 10.1631/jzus.B0920037 Project supported by the National Natural Science Foundation of China (No. 30570113) and the Research Fund for the Doctoral Program of Higher Education (No. 20060335008), China 2009-02-08 2009-06-29 2009-04-28 2022-01-05 Copyright © 2009, Journal of Zhejiang University Science 2009 Journal of Zhejiang University-SCIENCE B (Biomedicine and Biotechnology) 08 10