硅对向日葵水分利用效率的影响

以向日葵(Helianthus.annuus.L.cv.G101)为试验材料,研究了硅对营养液培养的向日葵生长和水分利用效率的影响。结果表明,施硅显著增加向日葵的水分利用效率,对向日葵生物量、叶面积的影响不大,却使最大展开叶的SPAD值显著增加;施硅显著降低了向日葵叶片背面的蒸腾速率以及叶片导度,而对叶片正面的蒸腾速率和叶片导度影响不大。同时,施硅向日葵木质部汁液的流速显著降低,体内硅含量增加。表明叶片蒸腾速率、叶片导度、木质部汁液流速的降低是硅提高向日葵水分利用效率的主要原因。     

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.     

Effect of silicon on photosynthetic gas exchange,photosynthetic pigments,cell membrane stability and relative water content of different wheat cultivars under drought stress conditions

This study aims to explain the effects of silicon (Si) foliar application on gas exchange characteristics, photosynthetic pigments, membrane stability and leaf relative water content of different wheat cultivars in the field under drought stress conditions. The experiment was arranged as a split-split plot based on randomized complete block design with three replications. Irrigation regime (100%, 60%, and 40% F.C.), silicon (control and Si application) and wheat cultivars (Shiraz, Marvdasht, Chamran, and Sirvan) were considered as main, sub and sub-sub plots, respectively. This study was carried out at the Research Farm of the Collage of Agriculture, Shiraz University, Iran, during 2012–2013 growing season. The results showed that foliar application of silicon increased the leaf relative water content, photosynthesis pigments (chlorophyll a, b and total chl and carotenoids), chlorophyll stability index (CSI) and membrane stability index (MSI) in all wheat cultivars, especially in Sirvan and Chamran (drought tolerant cultivars), under both stress and non-stress conditions. However, more improvement was observed under drought stress as compared to the non-stress condition. In contrast, these parameters decreased under drought stress. Si significantly decreased electrolyte leakage in all four cultivars under drought stress conditions. Furthermore, the intercellular carbon dioxide (CO₂) concentration (C_i) increased under drought stress. Si application decreased C_i especially under drought stress conditions. Net photosynthesis rate (A), transpiration rate (E) and stomatal conductance (g_s) were significantly decreased under drought conditions. Under drought, Si applied plants showed significantly higher leaf photosynthesis rate, transpiration rate, and stomatal conductance. Intrinsic water use efficiency (WUEi) and carboxylation efficiency (C_E) decreased in all cultivars under drought stress. However, the silicon-applied plants had greater WUEi and C_E under drought stress. The stomatal limitation was found to be higher in stressed plants compared to the control. Exogenously applied silicon also decreased stomatal limitation. Overall, application of Si was found beneficial for improving drought tolerance of wheat plants.     

GAS EXCHANGE AND GROWTH OF TRITICALE SEEDLINGS UNDER DIFFERENT NITROGEN SUPPLY AND WATER STRESS

The effect of nitrogen (30 and 120 mg N per cuvette) on photosynthetic rate of four cultivars of triticale (‘Bolero’, ‘Grado’, ‘Largo’, and ‘Lasko’) grown 14 days in phytotron was strongly modified by water content (75, 45 and 35% of full water capacity). For plants grown under 35% of full water capacity, it was higher when they were grown under 30 than under 120 mg N/cuvette (9.88 and 8.76 μmol CO₂ m^?2 s^?1, respectively) but for plants grown under 45 and 75% of full water capacity there were not significant differences. Transpiration, stomatal conductance, photosynthetic water use efficiency, and internal water use efficiency were not influenced by nitrogen doses independently of water content. Photosynthetic rate, transpiration, stomatal conductance, photosynthetic water use efficiency, and dry matter of studied cultivars of triticale grown under 45 and 35% of full water capacity and both nitrogen doses were lower than for plants grown under 75% of full water capacity. With lowering of water content stomatal conductance was decreasing similarly as photosynthetic rate e.g. for plants grown under 35% of full water capacity as compared with those grown under 75% of full water capacity average stomatal conductance decreased from 0.209 to 0.138 mol H₂O m^?2 s^?1 and photosynthetic rate from 13.69 to 9.32 μmol CO₂ m^?2 s^?1 and as a result there were not significant differences in internal water use efficiency for all studied combinations (67.09 μmol CO₂ mol^?1 H₂O) which shows that stomatal factors were mainly responsible for changes of photosynthetic rate. With lowering of water content from 75 to 35% of full water capacity the decrease of photosynthetic rate and stomatal conductance was much higher than the decreases of transpiration (from 3.57 to 3.02 mmol H₂O m^?2 s^?1) what shows not direct dependence of transpiration on stomatal conductance (water use efficiency decreased from 3.87 to 3.10 μmol CO₂ mmol^?1 H₂O). The effect of nitrogen on dry matter production was strongly modified by water availability e.g. for plants grown under 35% of full water capacity, dry matter was similarly independent of nitrogen dose but for plants grown under 45 and 75% of full water capacity dry matter was significantly higher than when they were grown under 120 (79.05 and 86.75 mg, respectively) or with 30 mg N/cuvette (74.03 and 80.30 mg, respectively).     

Silicon Improves Water Use Efficiency in Maize Plants

Abstract

The influence of silicon (Si) on water use efficiency (WUE) in maize plants (Zea mays L. cv. Nongda108) was investigated and the results showed that plants treated with 2 mmol L^?1 silicic acid (Si) had 20% higher WUE than that of plants without Si application. The WUE was increased up to 35% when the plants were exposed to water stress and this was accounted for by reductions in leaf transpiration and water flow rate in xylem vessels. To examine the effect of silicon on transpiration, changes in stomata opening were compared between Si-treated and nontreated leaves by measuring transpiration rate and leaf resistance. The results showed that the reduction in transpiration following the application of silicon was largely due to a reduction in transpiration rate through stomata, indicating that silicon influences stomata movement. In xylem sap of plants treated with 2 mmol L^?1 silicic acid, the Si concentration was 200-fold higher, while the Ca concentration which is mainly determined by the transpiration rate, was 2.5-fold lower than that of plants grown without Si. Furthermore, the water flow rate in xylem vessels of plants with and without Si was compared. Flow rate in plants with 2 mmol L^?1 Si was 20% lower than that without Si, which was accounted for by the increased affinity for water in xylem vessels induced by silica deposits. These results demonstrated the role of Si in improving WUE in maize plants.     

Water status and stomatal behaviour of cowpea,Vigna unguiculata (L.) Walp,plants inoculated with two Glomus species at low soil moisture levels

The effects of arbuscular mycorrhizal (AM) fungi on water status and stomatal behaviour of cowpea, Vigna unguiculata (L.) Walp. cv. B89-504, under water-stressed conditions in the greenhouse were studied. The 3 × 2 experimental design included two levels of mycorrhizal colonisation (Glomus mosseae, Glomus versiforme) and non-mycorrhizal control treatment and two soil moisture levels (well-watered pots and pots allowed to dry). Relative water content and leaf water potential values were higher in well-watered mycorrhizal and non-mycorrhizal plants than in water-stressed mycorrhizal and non-mycorrhizal plants. AM species had no significant effect on leaf osmotic potential, stomatal conductance and leaf transpiration in both well watered and water-stressed plants. The values of stomatal conductance and leaf transpiration were high during the vegetative stage and low during the flowering stage. These responses which can be related to the age of the plant suggest that mycorrhizal colonisation did not affect stomatal closure of cowpea plants during water stress. The decrease in plant growth and dry matter production in both mycorrhizal and non-mycorrhizal plants shows that drought resistance in cowpea was unaffected by mycorrhiza in the vegetative phase.     

Boron foliar fertilization of soybean and lychee: Effects of side of application and formulation adjuvants

Experiments to assess the rate of absorption and translocation of foliar‐applied, isotopically labeled boric acid (BA) were carried out with lychee (Litchi chinensis Sonn.) and soybean (Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl₂ and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of ¹⁰B to other leaf parts and no effect of adjuvants in increasing ¹⁰B absorption were recorded. In contrast, ¹⁰B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of ¹⁰B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased ¹⁰B absorption and enhanced acropetal ¹⁰B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl₂ in combination with 500 mM sorbitol decreased the rate of ¹⁰B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal ¹⁰B translocation was very limited. A distinct effect of B‐sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.     

Coupled model of stomatal conductance–photosynthesis–transpiration for paddy rice under water-saving irrigation

To improve the performance of a coupled model based on a Leuning–Ball stomatal conductance (g_s) model for rice under water deficit conditions, leaf temperature rising (ΔT) was incorporated into the Leuning–Ball model and a revised coupled model for simulation of stomatal conductance g_s–net photosynthesis rate (P_n)–transpiration rate (T_r) was developed based on data collected from a rice paddy with nonflooded controlled irrigation in 2003 and 2004. Both a Leuning–Ball and revised Leuning–Ball and coupled model based on both were evaluated with internal conductance (g_ic) determined by different equations. The performance of the Leuning–Ball model was improved under water deficit condition by incorporating ΔT, and the revised Leuning–Ball model performed better than the Leuning–Ball model in the coupled model of stomatal conductance–photosynthesis–transpiration for rice under water deficit conditions. Meanwhile, accuracy in g_ic calculation is essential for simulation of P_n, but not for simulation of T_r. Thus, leaf temperature rising ΔT is suitable as a leaf water status indicator in a simulation of rice leaf gas exchange response to water deficit conditions.     

施硅对玉米生长及蒸腾速率的影响

以玉米为试验材料,研究了土培条件下施Si与水分胁迫对玉米生长、蒸腾速率、叶片ABA浓度等的影响。结果表明:无论是否存在水分胁迫,施Si对玉米地上部生物量无显著影响;无论是否施Si,停止供水4d后玉米生物量明显降低;施Si显著降低了玉米植株的蒸腾速率,停止供水后其蒸腾速率明显低于正常水分供应处理,且随胁迫时间的延长,蒸腾速率逐渐降低;无论是否存在水分胁迫,施Si明显增加了玉米叶片的ABA浓度,同时水分胁迫增加了玉米叶片的内源ABA浓度。     

Improvement of drought tolerance in Tobacco (Nicotiana rustica L.) plants by Silicon

Ameliorative effect of silicon (Si) (2 mM as sodium silicate (Na₂SiO₃)) was studied in tobacco (Nicotiana rustica L.) plants grown under control at 100% field capacity (FC), mild drought (60% FC), and severe drought (30% FC) conditions. Si-treated plants had higher biomass of particularly above-ground parts both under drought and control conditions. Plants with Si supply had significantly higher net assimilation rates but lower transpiration rates. Silicon supply enhanced osmotic potentials only in the leaves, but not in the roots. A considerable rise in the concentrations of soluble sugars was observed particularly in the leaves under both drought and Si treatments. Soluble proteins, free α-amino acids, and proline concentrations increased in Si-treated plants under all watering treatments. Si enhanced the activity of antioxidative enzymes and decreased hydrogen peroxide (H₂O₂) concentrations. Results indicate that Si supplementation alleviates drought stress via improvement of water relation parameters, enhancement of photosynthesis, and elevation of antioxidant defenses.     

Effect of drought pretreatment before anthesis and post-anthesis waterlogging on water relation,photosynthesis, and growth of tomatoes

The effect of drought preconditioning before anthesis and post-anthesis waterlogging on water relation, photosynthesis, and growth was studied in tomatoes. Tomatoes were grown in pots and exposed to four treatments, whereby the plants were irrigated to 80% field capacity in T1 (control) and T2, 70% of the control (T3), and 50% of the control (T4). Drought was maintained for 30 days from 14 days after transplanting (DAT), and then the plants under T2, T3, and T4 were subjected to waterlogging at 60 and 80 DAT and lasted for 2 days. The results showed that drought pretreatments induced a decrease in leaf water potential, leaf insertion angle, photosynthetic rate, and transpiration rate. The stomatal closure and epinasty observed in response to drought pretreatment represented adaptive mechanisms to the followed waterlogging. The soil redox potential, photosynthetic rate, stomatal conductance, and transpiration rate of un-pretreatment were dramatically decreased by post-anthesis waterlogging; however, T3 was found to effectively enhance tolerance to a waterlogging event by decreasing leaf insertion angle and increasing photosynthetic rate, stomatal conductance, and transpiration rate. Fruit quality and yield were deteriorated considerably by waterlogging. However, T3 caused less damage to fruit quality and yield by post-anthesis waterlogging compared to T2.     

Effects of Silicon on Photosynthesis of Young Cucumber Seedlings Under Osmotic Stress

Effects of silicon (Si) application on photosynthesis of solution-cultured cucumber seedlings were investigated under osmotic stress and unstressed conditions. In unstressed conditions, silicon application had no effect on growth and photosynthetic parameters. The responses of the photosynthetic parameters to abruptly imposed osmotic stress did not differ between silicon treatments. After 1 week exposure to osmotic stress, growth reduction was observed, but it was less severe in seedlings grown with silicon than in those without silicon. Although there were no differences between silicon treatments in stomatal conductance, transpiration rate, cuticular transpiration, or xylem sap exudation rate under osmotic stress, leaf intercellular carbon dioxide (CO₂) concentration was significantly lower and photosynthetic rate tended to be higher in seedlings supplied with silicon. These results suggested that the silicon-induced alleviation of growth reduction under osmotic stress in cucumber was due to amelioration of stress-induced damage of leaf tissues rather than to improvement of leaf water status.     

Silicon alleviates mercury toxicity in garlic plants

Abstract

Silicon (Si) can increase plant stress tolerance. Mercury (Hg) is one of the major elements of heavy metal pollution. However, little attention has been paid to the possible effect of Si on Hg toxicity in plants. Here, the effects of Si on growth, photosynthesis, Hg accumulation and antioxidant defense were investigated in garlic grown in pots under Hg stress. Before sowing, Hg and Si were added at 3?mg Kg^?1 and 500?mg Kg^?1, respectively. The treatments included CT (control), Si, Hg and Hg?+?Si. The results showed that in non-stress conditions, added Si did not affect the garlic growth, photosynthetic gas exchange, malonaldehyde concentration or activities of antioxidant enzymes in leaves, except that it increased the superoxide dismutase activity. Under Hg stress, the garlic growth, leaf net photosynthetic rate, stomatal conductance, transpirational rate and superoxide dismutase activity in leaves were all inhibited, while the malondialdehyde concentration was increased; whereas these changes were all reversed in the presence of added Si. Added Si significantly decreased Hg concentrations in the root, bulb and shoot, and it also decreased exchangeable Hg level in the soil. These results suggest that Si could alleviate Hg toxicity in garlic through improving antioxidant defense ability, and decreasing Hg availability in soil and thus Hg uptake.     

玉米毛状根再生植株对水分胁迫的响应

为研究玉米根系对水分胁迫的响应,以玉米毛状根再生植株为材料,在水分胁迫下,测量其生育时期的植株生长和生理指标。结果表明,水分胁迫下玉米毛状根再生植株光合速率、蒸腾速率、细胞间隙CO2浓度、气孔导度均较高。水分胁迫下,毛状根再生植株的根系水导降幅最小,为13.2%,对照品种H99下降了84.7%。各营养器官含水率最高,叶渗透调节能力增强。这说明由于毛状根再生植株强大的根系,保证了植株生长发育过程中的水分供应和光合能力。     

Response of Sugarcane to Calcium Silicate on Yield,Gas Exchange Characteristics,Leaf Nutrient Concentrations,and Soil Properties in Two Different Soils

Silicon (Si), applied as calcium silicate (Ca-silicate), was evaluated for effects on yield; yield-contributing parameters in sugarcane, such as chlorophyll content, gas exchange characteristics, moisture content, and leaf nutrient concentrations; and soil fertility in the greenhouse in two different soil types. Seven levels of Si (0 20, 40, 60, 80, 120, and 150 g pot^–1) were tested by applying them with traditional fertilizers. Gas exchange characteristics such as photosynthesis, transpiration, and stomatal conductance were significantly greater with the plants fertilized with silicate over unamended control for both soils. Silicate fertilization increased chlorophyll and moisture contents in the top visible dewlap (TVD) leaf tissues, but results were not significantly better in both soils when compared with unamended control. In our 12-month study, we found that the Si content reached up to 2.64% and 1.86% per dry mass in TVD leaf tissues when amended with Ca-silicate fertilizer in soils 1 and 2, respectively. Results showed that as compared to unamended control, Si-amended treatments significantly increased maximum dry matter and cane yield by 77% and 66% in soil 1 and 41% and 15% in soil 2, respectively. With increasing silicate application, iron, copper, zinc, and manganese contents significantly decreased in leaf tissues and soil contents in both soils. Soil pH, Si contents, available sulfur, exchangeable Ca and magnesium, and cation exchange capacity were increased significantly more or less, whereas aluminum contents of soil decreased dramatically in both soils when amended with Ca-silicate. Our results indicate that different soil fertility status and rates of Si application are important factors influencing the yield, growth parameters, chlorophyll, and nutrient contents of sugarcane leaf as well as soil properties.     

设施栽培油桃对叶面施15N的吸收、分配特性研究

以设施栽培的5年生早红珠油桃/山毛桃为试材,应用15N示踪技术研究油桃叶片对15N-尿素的吸收及运转特性。结果表明,叶片施用15N-尿素标记叶吸收主要发生在叶片涂抹15N-尿素后6.h内,平均吸收速率为0.204mg/(g.h);标记叶中15N吸收量24.h达到最高,新梢和梢顶嫩叶15N含量在施用15N-尿素48.h达到最高,下部叶15N含量很低,没有明显的峰;处理168.h各器官中15N含量为标记叶梢顶嫩叶新梢下部叶;试验结束时分配势Ndff(即各器官N含量来自化肥N所占的百分率)为标记叶中最高,然后依次为梢顶嫩叶、新梢、下部叶。这说明氮素迅速被吸收并运到嫩梢和嫩叶中,从而促进这些新生器官的形态建造,可起到以N增C的作用。不同叶面处理的试验还表明,正面和背面全部涂抹的叶片15N含量最高,只涂抹叶片背面次之,涂抹正面最低。设施栽培油桃叶片可迅速吸收尿素,其吸收量早晨明显优于中午和下午,因此设施油桃栽培管理中于早晨进行叶面施尿素,且正反面兼顾,N素的吸收利用效果最好。     

Responses of a salt‐tolerant and a salt‐sensitive line of sunflower to varying sodium/calcium ratios in saline sand culture

The effects on two‐week‐old plants of a salt‐tolerant line (Euroflor) and a salt‐sensitive (SMH‐24) line of sunflower, of varying sodium/calcium (Na/ Ca) ratios in a saline growth medium were assessed after three weeks growth in sand culture under greenhouse conditions. The different Na/Ca ratios of the salt treatment were 36.5, 74.0, and 149, at a constant concentration of 150 mol m^‐3 NaCl. Euroflor was superior to SMH‐24 in fresh and dry matters of shoots and roots at varying external Na/Ca ratios. The leaf Na⁺ concentration in SMH‐24 increased consistently with increase in external Na/Ca ratio, whereas that in Euroflor remained almost unaffected. Although leaf chlorine (Cl^‐) was significantly greater in SMH‐24 than Euroflor, there was no effect of decreasing Ca²⁺ concentration of the saline growth medium on the leaf Cl^‐ concentrations of both lines. The lines did not differ in K⁺, Ca²⁺ or Mg²⁺ concentrations of both shoots and roots. The leaf K/Na and Ca/ Na ratios, K versus Na selectivity were considerably higher in Euroflor than in SMH‐24. The lines also did not differ in leaf water potential and gas exchange and these variables were not affected due to decreasing Ca²⁺ concentration of the saline growth medium. Stomatal conductance and transpiration remained unchanged in Euroflor, whereas those in SMH‐24 decreased significantly at the highest external Na/Ca ratio. Euroflor had significantly greater stomatal conductance and transpiration than those of SMH‐24 at almost all external Na/Ca ratios, whereas the reverse was true for water use efficiency. It was established that Euroflor was tolerant to low Ca²⁺ concentrations of the saline growth medium as compared with SMH‐24. This was mainly attributable to accumulation of relatively low Na⁺ and Cl^‐ in the leaves, and maintenance of high leaf K/Na and Ca/Na ratios and K versus Na selectivity in Euroflor.     

Silicon‐induced cadmium resistance in rice (Oryza sativa)

Silicon (Si)‐induced cadmium (Cd) tolerance in rice (Oryza sativa L.) was investigated by analyzing Cd uptake, growth, and physiological parameters. Silicon treatments (0.0, 0.2, or 0.6 mM) were added to 6 d–old seedlings, and Cd treatments (0.0 or 5.0 μM) were added to 20 d–old seedlings. Parameters determined included: maximum net CO₂ assimilation (A_max), stomatal conductance (g_smax), and transpiration (E_max) rates at varying intercellular CO₂ concentrations (C_i). Also measured were chlorophyll fluorescence, growth, and Cd‐uptake parameters. Results showed a Si‐induced inhibition of Cd uptake. However, 0.2 mM or 0.6 mM Si treatment concentrations did not differentially inhibit Cd uptake or differentially alleviate Cd‐induced growth inhibition, despite a significant increase in tissue Si concentration due to 0.6 mM Si treatment compared to 0.2 mM Si treatment. Additionally, photosynthesis and chlorophyll‐fluorescence analysis showed that treatment with Cd significantly inhibited photosynthetic efficiency. Interestingly, the addition of 0.2 mM Si, more so than the addition of 0.6 mM Si, significantly alleviated the inhibitory effects of Cd toxicity on photosynthesis and chlorophyll‐fluorescence parameters. Our results suggest that 0.2 mM Si could be close to an optimum Si‐dose requirement for the alleviation of toxicity symptoms mediated by moderate (5 μM) Cd exposure.     

Photosynthetic Response of Maize Plants Against Cadmium and Paraquat Impact

The effects of cadmium (Cd) and/or paraquat (PQ) toxicity on photosynthesis in maize leaves were examined by measurement of gas exchange and chlorophyll content in hydroponically cultured plants. It was found that growth rate was distinctly influenced only by 100 µM Cd treatment. Chlorophyll a and chlorophyll b decreased along with the increase of Cd concentration, while PQ spraying, alone and combined with Cd, increased chlorophyll a content on the third and seventh experimental days. Generally, carotenoid content increased in response to Cd and PQ and reached the highest levels at 100 µM Cd. Rate of photosynthesis in maize decreased after Cd treatment. CO₂ assimilation was approximately 60% reduced at 50 µM Cd and 70% reduced in the presence of 100 µM Cd. PQ toxicity was partly overcome after the third day of exposure. Transpiration and stomatal conductance in maize leaves decreased on the third day along with Cd concentration and PQ spraying, except for the 25-µM Cd-treated plants. On the tenth day, the 25-µM Cd-treated plants and those from PQ-treated variants showed an increase of transpiration and stomatal conductance. Maize exhibited an ability to accumulate Cd in high quantities, especially in the roots—over 4,500 mg Cd/kg dry weight.     

Permeability of peach leaf cuticles to boron

Isolated leaf cuticles and intact plants of one‐year‐old potted ‘Red Haven’ trees grown in the greenhouse were used to study the permeability of leaf cuticles to boron (B). The isolated leaf cuticles were prepared enzymatically. Flux was determined using a transport cell. Permeability coefficient (P) was calculated and used as the parameter of cuticle permeability to B. For intact plant studies, enriched‐¹⁰B boric acid solution was evenly spread onto the abaxial or the adaxial side of a leaf. The trees were sacrificed three days after the treatment and selected plant parts were analyzed with ICP‐AES and ICP‐MS spectrometers. The ¹⁰B content was used as the parameter of B permeability in vivo. The permeability coefficient of peach leaf adaxial cuticle was in the order of 10^‐7 cm/sec. There were no difference in the permeability coefficients among B concentration and surtactant treatments. The pH had variable effect on B absorption through the cuticle of the adaxial side of the leaf. For the in vivo study of B uptake by peach leaves, the abaxial side was more efficient than the adaxial side, with the total ¹⁰B taken up four times greater in the abaxial side than the adaxial side. The absorption percentages of the total ¹⁰B applied in the abaxial and adaxial sides were 0.31% and 0.08%, respectively. Scratches on the treated leaves made the total ¹⁰B uptake and translocation higher than the control treatment.