ALLEVIATION EFFECT OF DIFFERENT RATIOS OF Al TO Ca ON Al TOXICITY FOR MORPHOLOGICAL GROWTH OF MUNGBEAN SEEDLING

Aluminum (Al) is one of the major factors limiting plant production in acid soils. Calcium (Ca) plays a very important role in the response of plants to salt stress. Little information is available about ratios of Al/Ca on the growth of mungbean seedlings under Al stress. Mungbean seedlings were grown in solution with combined concentrations of Al (0, 2, and 5 mM) and Ca (0–10 mM) in a randomized complete block design experiment for 16 days, to evaluate effects of the ratios on alleviation of Al toxicity for the morphological growth under Al stress. The results showed that Al0 + CaO significantly decreased the epicotyl length, seedling height, root length, fresh weight, and dry weight by 25%, 15%, 16%, 16%, and 16%, respectively, compared with a control (Al0 + Ca0.5). At 2mM Al without Ca in the solution (Al2 + Ca0), the epicotyl length, seedling height, root length, fresh weight, and dry weight were decreased by 26%, 12%, 12%, 14%, and 12%, respectively, compared with a control (Al2 + Ca0.5). At 5mM Al without Ca in the solution (Al5 + Ca0), the epicotyl length, seedling height, root length, fresh weight, and dry weight were also decreased by 16%, 8%, 4%, 9%, and 7%, respectively, compared with a control (Al5 + Ca0.5). At 2mM Al stress, with the ratio of Al/Ca = 1:2 (Al2 + Ca4), the epicotyl length, seedling height, and fresh weight increased 13%, 5%, and 15%, respectively, compared with the control (Al2 + Ca0.5). While at 2mM Al stress, the root length at Al/Ca = 2:1 (Al2 + CA1) and dry weight at Al/Ca = 1:1 (Al2 + Ca2) were shown to be increased by 4% and 5%, respectively. At 5mM Al stress, with the ratio of Al/Ca = 2:1 (Al5 + Ca2.5), the epicotyl length, seedling height, and fresh weight increased 12%, 4%, and 7%, respectively, compared with the control (Al5 + Ca0.5). However, the root length and dry weight with the ratio either of Al/Ca = 2:1, 1:1 or 1:2, had no ameliorating effect, but was shown to have a negative effect, compared with the control (Al5 + Ca0.5). This suggests that the alleviation effect and its extent of Ca on Al toxicity for the seedling morphological growth are dependent on characters, the degree of Al stress, and the ratio of Al to Ca.     

Boron amelioration of aluminum toxicity in mungbean seedlings

Boron (B) amelioration of aluminum (Al) toxicity was studied for growth of mungbean (Phaseolus aureus Roxb.) seedlings and cuttings (without roots) in a growth chamber. Mungbean seedlings and cuttings were grown in the solution with combinations of three concentrations of B (0,5, and 50 μM) and three concentrations of Al (0, 2, and 5 mM) in randomized complete block design experiments for 16 days. Results showed that B significantly promoted elongation of epicotyls and hypocotyls, and increased height of seedlings grown under Al stress. Boron also increased fresh weight of seedlings in high Al solution. Treatment of plants grown with high B and Al stress had no apparent effect on fresh and dry weights of seedling roots. Seedling dry weight increased significantly by adding high B to solutions with 2 mM or 5 mM Al. No significant differences were observed between the high B treatment and the control (normal B, 5 μM) in lengths of epicotyls and fresh and dry weights of mungbean cuttings grown under Al stress. High concentrations of B decreased soluble protein and increased chlorophyll in seedlings treated with 2 mM Al. Boron had no amelioration effect on cuttings grown with Al, although Al increased soluble protein. Our results suggested that B alleviation of Al toxicity was related to root function and Al toxicity may possibly be due, in part, to B deficiency.     

Silicon stimulates initial growth and chlorophyll a/b ratio in rice seedlings,and alters the concentrations of Ca,B, and Zn in plant tissues

Abstract

Silicon (Si) is considered a beneficial element for plants due to the far-reaching benefits it confers, including enhanced growth, yield, and crop quality, as well as stress resistance. In this study, we evaluated the effect of Si during germination and initial growth (0.0, 0.5, 1.0, or 1.5?mM Si) and during vegetative growth (0, 1, 2, or 3?mM Si) in rice (Oryza sativa) cv. Morelos A-98. Si did not affect germination but stimulated seedling height, root length, number of roots, as well as fresh and dry biomass weight of shoots and roots during initial growth. During vegetative growth, the application of 3?mM Si significantly increased the chlorophyll a/chlorophyll b ratio, but no major changes were observed either in growth or in concentrations of most nutrients, with the exception of Ca (which increased with 3?mM Si), and B and Zn (which decreased in the presence of Si). In conclusion, applying Si had positive effects during the initial stage of growth, increasing seedling height, root length, root number, and fresh and dry biomass weight. Under our experimental conditions, Si did not affect germination and vegetative growth, but increased Ca concentrations and decreased B and Zn concentrations.     

Silicon Effect on Nutrient Acquisition of Peanut (Arachis hypogaea L.) Under Aluminum Stress

Aluminum (Al) toxicity represents one of the main yield-limiting factors for crops in acid soils. Silicon (Si) is known to increase tolerance in higher plants. This study was conducted to determine whether treatment with Si could improve nutrient uptake by peanut under Al stress. Peanut (Arachis hypogaea L. cv Zhonghua 4) was raised with or without Si (1.5 mM) in the growth chamber under 0 and toxic Al (0.3 mM) levels. Aluminum stress significantly decreased the root- and total-dry weight by 52.4% and 32.0%, respectively. The content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) was significantly decreased, but that of Al increased markedly in shoots and roots after Al exposure at seedling, flower-needle, and pod-setting stage. Silicon alleviates Al toxicity in peanut plants in relation to Al distribution and allocation of tissue P, K, Ca, and Mg by favoring the partitioning of dry mass to roots.     

Effects of Boron on Aluminum Toxicity on Seedlings of Two Soybean Cultivars

Boron (B) is an essential micronutrient for higher plants. It has been suggested that addition of B at an optimal concentration might alleviate Al toxicity. Little information is available about B effects on soybean seedling growth under Al stress and differential alleviation of B on Al toxicity. In the present study, the seedlings of two soybean cultivars (Williams and Nanrong 73-935) were grown in a solution with factorial combinations of Al (0, 2, and 5 mM) and B (0, 5, and 50 μM) in a randomized complete block design experiment for 18 days. The results showed that high B was found to ameliorate Al toxicity by significantly increasing the growth characters including root length under 2 mM Al stress, and epicotyl length and fresh weight under 5 mM Al stress of the two cultivars. However, high B concentration did not significantly increase chlorophyll content under Al stress. Williams was more sensitive than Nanrong 73-935 on the growth characters and chlorophyll content under double stresses (B deficiency combined with Al toxicity), although they had similar sensitivity to B deficiency stress alone for growth characters. In addition, high B concentration was found to cause toxicity symptoms on root length and older leaves of both cultivars under no Al stress.     

Silicon effect on growth,nutrient uptake,and yield of peanut (Arachis hypogaea L.) under aluminum stress

Abstract

The objective of this study was to investigate the effect of silicon (Si) on growth, nutrient uptake, and yield of peanut under aluminum (Al) stress. Peanut (Arachis hypogaea L. cv. Zhonghua 4) raised with or without Si (1.5?mM) in the growth chamber under 0 and toxic Al (0.3?mM) levels. Aluminum stress significantly decreased the biomass and root dry weight by 12.9% and 10.7%, and the pod yield, number of mature pod per plant and seed number of per pod by 16.7%, 10.7%, and 13.9%. The content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) was significantly decreased, but that of Al increased markedly in shoots and roots of peanut after Al exposure at seedling, flower-needle and pod-setting stage. Under Al stress condition, Si application protected peanut by improving nutrient uptake at different growth stages and favoring the partitioning of dry mass to pod and the allocation of tissue N, P, K, Ca, and Mg to shoots and pod and decreasing Al uptake and accumulation.     

PHYSIOLOGICAL EFFECTS OF ALUMINUM/CALCIUM RATIOS ON ALUMINUM TOXICITY OF MUNGBEAN SEEDLING GROWTH

Mungbean seedlings were grown in a nutrient solution with combined concentrations of aluminum (Al) (0, 2, and 5 mM) and calcium (Ca) (0–10 mM) in a randomized complete block design experiment for 16 days. The results showed that under no Al stress, Al0 + Ca0 decreased chlorophyll content by 10%, increased soluble protein, free proline content, and electrolyte leakage by 51%, 533%, and 111%, respectively, compared with a control (Al0 + Ca0.5). Under 2mMAl stress, Al2 + Ca0 decreased chlorophyll content by 19%, increased soluble protein, free proline content, and electrolyte leakage by 48%, 405%, and 55%, respectively, compared with a control (Al2 + Ca0.5). The ratio of Al/Ca = 1:2 increased chlorophyll content by 3%, decreased free proline content and electrolyte leakage by 64% and 34%, respectively. However, all of Al/Ca = 2:1, 1:1 and 1:2 at 2AlmM significantly increased soluble protein, compared with Al2 + Ca0.5. Under 5mMAl stress, Al5 + Ca0 decreased chlorophyll content by 11%, and increased soluble protein, free proline content, and electrolyte leakage by 77%, 85%, and 30%, respectively, compared with a control (Al5 + Ca0.5). The ratio of Al/Ca = 1:2 increased chlorophyll content by 14%, decreased free proline content by 80%, and electrolyte leakage by 34%, compared with Al5 + Ca0.5. However, all ratios of Al/Ca = 2:1, 1:1 and 1:2 at 5mMAl also significantly increased soluble protein, compared with the control. Furthermore, it was observed that Al/Ca = 1:2 could accumulate more Al and Ca in the seedlings than Al/Ca = 2:1 and 1:1 regardless of Al stress (2mM or 5mMAl). Lack of Ca affected the synthesis of chlorophyll, increased soluble protein and free proline, and enhanced electrolyte leakage. Al/Ca = l:2 might be an appropriate ratio for physiological alleviation of Al toxicity to mungbean seedling growth. High concentration of Ca in the solution at appropriate Al/Ca ratio (e.g. Al/Ca = 1:2) could increase chlorophyll content, an indication of alleviation effect. On the contrary, the high Ca caused a significant increase of soluble protein. It suggests the involvement of various proteins that have properties to resist Al toxicity for mungbean seedling growth.     

Silicon Ameliorates the Adverse Effects of Salinity on Turfgrass Growth and Development

An experiment was conducted to assess the effect of foliar application of potassium silicate on Cynodon dactylon [L.] Pers., Festuca arundinacea Schreb. and Lolium perenne L. With increased salinity level, chlorophyll content and relative water content (RWC) in these three turfgrasses were reduced significantly when compared with the untreated control. Supplementary silicon (Si) ameliorated the adverse effects of salinity on chlorophyll content. Silicon treatments decreased proline at all salinity levels. Moreover, addition of Si increased shoot length and shoot number in all turfgrasses. Sodium (Na) concentration was increased in both leaves and roots of turfgrasses at high salinity level; however, Si treatment significantly reduced Na concentration in all of them. Silicon increased Potassium concentration in shoots and roots (though not significantly) in most cases. It can be concluded that Si alleviated the adverse effects of salt stress in all turfgrasses.     

Cadmium (Cd) and Lead (Pb) Induced Changes in Growth,Some Biochemical Attributes,and Mineral Accumulation in Two Cultivars of Mung Bean [Vigna radiata (L.) Wilczek]

Addition of cadmium, lead, and cadmium + lead (Cd, Pb, and Cd+Pb) to growth medium leads to a reduction in seed germination, length, fresh and dry biomass of shoots and roots, total chlorophyll, chlorophyll a, chlorophyll b, and soluble proteins in plants. This study was undertaken on two mungbean cultivars (MN-92 and MN-98). Application of these metals in the growth medium reduced the bioabsorption of calcium (Ca), magnesium (Mg), and potassium (K). Concentrations of all the metals were greater in the roots than in the shoots except for K, which was greater in the shoots. Mungbean cultivar NM-98 performed better than NM-92 in response to heavy-metal toxicity. Overall, the metal-induced physiobiochemical changes resulted in reduced growth of both mungbean cultivars.     

Silicon-induced changes in growth,ionic composition,water relations,chlorophyll contents and membrane permeability in two salt-stressed wheat genotypes

We investigated the effect of exogenously applied silicon (Si) on the growth and physiological attributes of wheat grown under sodium chloride salinity stress in two independent experiments. In the first experiment, two wheat genotypes SARC-3 (salt tolerant) and Auqab 2000 (salt sensitive) were grown in nutrient solution containing 0 and 100 mM sodium chloride supplemented with 2 mM Si or not. Salinity stress substantially reduced shoot and root dry matter in both genotypes; nonetheless, reduction in shoot dry weight was (2.6-fold) lower in SARC-3 than in Auqab 2000 (5-fold). Application of Si increased shoot and root dry weight and plant water contents in both normal and saline conditions. Shoot Na⁺ and Na⁺:K⁺ ratio also decreased with Si application under stress conditions. In the second experiment, both genotypes were grown in normal nutrient solution with and without 2 mM Si. After 12 days, seedlings were transferred to 1-l plastic pots and 150 mM sodium chloride salinity stress was imposed for 10 days to all pots. Shoot growth, chlorophyll content and membrane permeability were improved by Si application. Improved growth of salt-stressed wheat by Si application was mainly attributed to improved plant water contents in shoots, chlorophyll content, decreased Na⁺ and increased K⁺ concentrations in shoots as well as maintained membrane permeability.     

铝胁迫对不同耐铝大麦基因型干物质积累与铝和养分含量的影响

以苗期表现为耐铝性具有明显差异的 10份大麦基因型为材料 (耐铝和铝敏感基因型各 5个 ) ,研究铝胁迫条件下生育后期植株生物量、铝和养分元素含量的差异。结果表明 ,铝胁迫抑制植株干物质积累 ,但抑制程度因基因型而异 ,上 70 119等铝敏感基因型受影响较大 ,且两类基因型之间的差异成熟期明显大于乳熟期。铝胁迫显著降低敏感基因型的子粒产量 ,但对耐性基因型的影响较小。铝胁迫增加所有基因型根系和地上部的Al含量 ,但增加幅度基因型之间存在着明显差异 ,耐铝基因型增加较少 ,而铝敏感基因型表现显著增加。酸性土壤上 ,根系和地上部N、P、K、Ca、Mg和Zn等养分含量 ,铝敏感基因型显著减少 ,耐铝基因型受影响较小。     

硅对大麦铝毒的消除和缓解作用研究

在温室和实验室进行了施硅对消除或缓解大麦酸害铝毒的土培和溶液培养试验。结果表明,施硅后大麦幼苗的地上部茎、叶和地下部根的生物量均比不施硅明显增加。施硅能有效地促使植株吸收的铝在根部积累,抑制铝向地上部分运转;施硅还能调节根吸收的磷向地上部分运移,以减轻因伴随铝毒而产生的缺磷症状。施硅消除或缓解酸害铝毒的可能机理是:铝与硅形成无毒的铝硅酸复合离子(HAS),降低活性铝的浓度,及硅能调节大麦幼苗地上部和根内铝和磷的再分配。     

Accumulation of amino acids,proline, and carbohydrates in response to aluminum and manganese stress in maize

Synthesis of amino acids, proline, and carbohydrates was studied in roots and shoots of 5 maize accessions, differing in aluminum (Al) and manganese (Mn) tolerance, in response to Al and Mn stress at the seedling stage in solution culture. The concentrations of these metabolites increased in roots and shoots of the seedlings in the nutrient solution with added Al (0.22 mM), and Mn (2.0 mM). Both Al and/or Mn tolerant and non‐tolerant accessions accumulated more metabolites under stress than control. Generally, the tolerant accessions accumulated more solutes than the non‐tolerant maize accessions examined.     

Effect of Foliar Salicylic Acid Applications on Growth,Chlorophyll, and Mineral Content of Cucumber Grown Under Salt Stress

The objective of this study was to determine the effect of foliar salicylic acid (SA) applications on growth, chlorophyll, and mineral content of cucumber grown under salt stress. The study was conducted in pot experiments under greenhouse conditions. Cucumber seedlings were treated with foliar SA applications at different concentrations (0.0, 0.25, 0.50, and 1.00 mM). Salinity treatments were established by adding 0, 60, and 120 mM of sodium chloride (NaCl) to a base complete nutrient solution. The SA was applied with spraying two times as before and after transplanting. Salt stress negatively affected the growth, chlorophyll content and mineral uptake of cucumber plants. However, foliar applications of SA resulted in greater shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight as well as higher plants under salt stress. Shoot diameter and leaf number per plant increased with SA treatments under salt stress. The greatest chlorophyll content was obtained with 1.00 mM SA treatment in both saline and non-saline conditions. Leaf water relative content (LWRC) reduced in response to salt stress while SA raised LWRC of salt stressed cucumber plants. Salinity treatments induced significant increases in electrolyte leakage. Plants treated with foliar SA had lower values of electrolyte leakage than non-treated ones. In regard to nutrient content, it can be interfered that foliar SA applications increased almost all nutrient content in leaves and roots of cucumber plants under salt stress. Generally, the greatest values were obtained from 1.00 mM SA application. Based on these findings, the SA treatments may help alleviate the negative effect of salinity on the growth of cucumber.     

Beneficial effects of silicon nutrition in alleviating salinity stress in hydroponically grown canola,Brassica napus L., plants

Abstract

Silicon (Si) is the second most abundant element in soil and effectively counteracts the effects of various abiotic stresses, such as drought, heavy metal toxicity and salinity, on plants. In the present study the ameliorating effects of Si nutrition supplied as 2?mmol?L^?1 sodium silicate were investigated on hydroponically grown canola (Brassica napus L.) plants under salinity stress (i.e. 150?mmol?L^?1 sodium chloride). Salinity decreased plant growth parameters such as tissue fresh and dry weights. These decreases were accompanied by increased lignin contents, Na⁺ ion accumulation, increased lipid peroxidation and decreased chlorophyll contents in plants. Silicon nutrition, however, enhanced plant growth parameters and led to the prevention of lignin and the Na⁺ accumulation in shoots, reduced levels of lipid peroxidation in the roots and higher levels of chlorophyll. As a result of salinity, catalase activity in the whole plant and both soluble and cell wall peroxidase activities in the shoots decreased. Silicon nutrition, however, increased the reactive oxygen species scavenging capacity of salt-stressed plants through increased catalase and cell wall peroxidase activities. Thus, silicon nutrition ameliorated the deleterious effects of salinity on the growth of canola plants through lower tissue Na⁺ contents, maintaining the membrane integrity of root cells as evidenced by reduced lipid peroxidation, increased reactive oxygen species scavenging capacity and reduced lignification.     

The influence of increasing doses of silicon on maize seedlings grown under salt stress

The aim of this study was to evaluate the effect of increasing silicon (Si) doses (0, 1.0, 1.7, 3.0 mM) on two maize varieties (Kosmo 230 and SMH 220) grown under optimal and salt stress (60 mM sodium chloride (NaCl)) conditions. After 7 days of the cultivation, both growth and physiological parameters were determined. Application of Si improved some growth parameters, chlorophyll concentration and reduced malondialdehyde content. Kosmo 230 variety very well tolerated all concentrations of silicate and the highest dose significantly increased fresh and dry matter of plants grown under both optimal and stress conditions, meanwhile in SMH 220 some growth parameters were depressed. Si application enhanced chlorophyll content under stress conditions but did not alter fluorescence parameters. Reaction of Kosmo 230 variety to all three concentrations of silicate was more positive than SMH 220. Application of silicate may alleviate the negative effects of stress but needs a careful supply, especially at higher doses.     

Effect of salt stress on tomato plant and the role of calcium

Abstract

Salinity is one of the serious abiotic stresses that has adverse effects on plant growth. The aim of this study was to investigate the effect of sodium chloride (NaCl) on germination and growth parameters of tomato plant as well as the role of Ca²⁺as an ameliorating agent. 100?mM NaCl and two concentrations of calcium (5 and 10?mM) were applied to tomato seeds and seedlings. This study was carried out in a Completely Randomized Design (CRD) with a total of six treatments each comprising of three replicates. The application of 100?mM of NaCl delayed the germination time by 27.6%, reduced the seedling length and seedling vigor by 24.33% and germination stress tolerance by 27.6% as compared to control. Salinity also reduced the plant growth (root and shoot length, root fresh and dry weight, shoot fresh and dry weight, membrane stability, relative water content and leaf area), whereas the application of calcium mitigated the negative effects of salinity on germination and growth to a greater extent. With increased calcium concentration, growth and germination increased significantly both alone and in the salt-affected plant. 10?mM calcium showed best results and enhanced the promptness index by 20.7%, seedling length and vigor by 15.1% and GSI by 20.7%. It also improved root fresh and dry weight, shoot fresh and dry weight, relative water content and leaf area. Similarly, 5?mM calcium also increased plant height and membrane stability index. The present study suggests that application of Ca²⁺ enhanced the growth of tomato plant under saline conditions.     

Effects of potassium silicate and nanosilica on quantitative and qualitative characteristics of a commercial strawberry (fragaria × ananassa cv. ‘camarosa’)

Silicon (Si) is considered as a beneficial element to higher plants especially under stress conditions. A factorial experiment, in a completely randomized design with four replications, was used to investigate the effects of two application methods (spraying and soil drenching) and eight levels of Si compounds including 0, 5, 10 and 15 mM of potassium silicate (K₂SiO₃) and 0, 5, 10 and 15 mM of nanosilica (SiO₂). The results indicated that Si application (all or some treatments) decreased transpiration, specific leaf area, petiole length, and promoted the flowering, fruit firmness, leaf/crown number, fresh and dry weight of shoot and root, water use efficiency. They also showed it did not affect the fruit set percentage, yield, chlorophyll index, total soluble solid, leaf area, fresh and dry weight of crown, photosynthesis, stomatal conductance, internal carbon dioxide (CO₂) concentration and mesophyll efficiency of strawberry. The results suggest the beneficial effects of Si on growth and development of strawberry.     

施用接种解磷真菌的壮秧剂对水稻秧苗生长特性及磷素吸收的影响

通过苗床培养试验,研究了在低有效磷营养土上施用接种解磷青霉菌的壮秧剂对水稻秧苗的生长特性及磷素吸收的影响。结果表明,在低磷条件下,施用接种解磷菌的壮秧剂可以显著提高水稻秧苗的株高、地上部干、鲜生物量、根系活力、地上部磷含量和磷吸收量,在5个处理中,P2处理水稻秧苗的株高比对照提高16.81%,地上部鲜生物量比对照增加21.28%,地上部干生物量比对照增加12.42%,地上部磷含量比对照提高31.11%,地上部磷素吸收量比对照提高44.03%,表现效果较好,其次是P1和P4处理,其中P1处理的根部干、鲜生物量、根部的磷素含量和磷素吸收量均高于其他处理。在有效磷较低的土壤上,施用接种解磷菌的壮秧剂,可以促进作物苗期生长,分解土壤中难溶性磷,提高土壤磷素的利用效率。     

丛枝菌根对酸枣实生苗耐盐性的影响

本文研究了在土中加入不同量NaCl条件下 (0、1 5、3 0、4 5gkg-1干土 )接种丛枝菌根真菌 (AMF)Glomusmosseae对盆栽酸枣 (ZizyphusspinosusHu)实生苗生长及耐盐性的影响。结果表明 ,无论接种与否 ,植株的高度、根茎叶的干鲜重均随土壤NaCl浓度的增加而降低 ,而根、茎、叶和整株的Na浓度及Na全量均随土壤NaCl浓度的增加而增大。在土壤盐浓度相同的条件下 ,接种AMF植株的生长量 (株高、鲜重、干重等 )和叶片的叶绿素含量显著高于不接种植株。接种AMF的植株茎、叶中Na浓度低于不接种植株 ,而根中Na浓度、植株Na总量显著高于不接种植株。盐浓度最大的接种处理 ,其植株生长量和叶片叶绿素含量均高于不加盐不接菌处理。播种时进行盐胁迫处理和播种后 4 0d开始进行盐胁迫处理对菌根的侵染率、植株生长的影响差异不显著。上述四种盐浓度播种时进行盐处理的接种AMF植株的总干重比不接种植株分别提高 16 4 %、14 9%、4 8%、35 % ,在播种后 4 0d进行盐处理的接种AMF的植株比不接种植株分别提高 194 %、12 7%、72 %、4 6 %。结果证明 ,酸枣实生苗具有较强的耐盐性 ,其生长对菌根真菌有很强的依赖性 ,接种菌根真菌提高了其耐盐能力。