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1.
Powders prepared from sweetflag Acorus calamus rhizomes collected at both high (1700 m) and low (900 m) altitude in Eastern Nepal were admixed with wheat at concentrations in the range 0.05–2% w/w and the wheat infested with Sitophilus oryzae or S. granarius adults. Following a 7 day incubation, the mortality of both species was significantly lower at 20 °C than at 30 °C, and the material collected from high altitude was slightly less toxic than that from low altitude. The moisture content of the wheat (14 or 17%) and the part of the rhizome used to prepare the powder (young or mature growth) had no apparent effect on the toxicity of the preparation. Sitophilus granarius (L.) adults were more tolerant of the material than S. oryzae (L.), while the converse was true for larvae developing in treated grain. An admixture rate of approximately 2% w/w admixed rhizome powder was required to give complete kill of adults of both species following 7 days exposure at 20 °C, while a concentration of 1% w/w either prevented the emergence of adults or killed them rapidly following emergence when wheat containing eggs of either species was incubated for 7–8 weeks at 30 °C.

The β-asarone content of the rhizome powders was determined by GC-MS as 6.4 and 4.7% w/w (mature section of rhizomes collected at high and low altitudes, respectively) and 3.6 and 4.0% w/w (young sections of rhizomes collected at high and low altitudes, respectively). It is anticipated that, under field conditions and in the temperature range 20–30 °C, the initial residue of approximately 1300 mg/kg β-asarone required to disinfest wheat containing these weevil species would decline rapidly due to evaporation.  相似文献   


2.
The effects of relative humidity (RH) and temperature on tomato powdery mildew (Leveillula taurica) were studied in controlled environments to define conditions that affect disease development in fresh market tomatoes in California. Gradients of RH (20–90%) at constant temperatures (20–30°C) were generated in single growth chambers to determine their effect on mildew development on mature tomato plants. Temperatures of 30°C and above were deleterious for spore germination, germ tube elongation, and disease development. Lesion growth and rate of disease progress were significantly higher at 20°C than at 25°C. Low RH levels (20–40%) reduced spore germination and lesion growth, accelerated host tissue death and reduced disease progress. Intermediate RH levels (50–70%) increased spore germination and optimized disease development, provided temperatures were maintained within favorable limits. High RH levels (80–90%) were favorable for spore germination but continued exposure to these conditions led to a limited lesion growth and disease progress. Short daily periods (two or three daily exposures of at least 2 h) of high temperatures (35°C) suppressed disease development by 70–92%.  相似文献   

3.
Lantana camara is an ornamental plant used in traditional medicine for the treatment of various diseases. The roots of L. camara is a rich source of oleanolic acid which has shown anti-inflammatory, hepatoprotective, antitumor, antioxidant and anti-hyperlipidemic activity. Optimization of various extraction parameters using response surface methodology (RSM) was performed to assess maximum yield of oleanolic acid from L. camara roots. Plackett–Burman design criterion was applied to identify the significant effects of various extraction parameters such as temperature, time, mean particle size, solvent–solid ratio, solvent composition and number of extraction steps on extraction of oleanolic acid. Among the six variables tested extraction time, mean particle size, solvent–solid ratio and solvent composition were found to have significant effect on oleanolic acid extraction. Optimum levels of the significant variables were determined by using a central composite design. The most suitable condition for extraction of oleanolic acid was found to be a single step extraction at extraction temperature 35 °C, extraction time 55 min, solvent–solid ratio 55:1, mean particle size 0.5 mm and solvent composition 52.5% methanol in a methanol-ethyl acetate mixture. At these optimum extraction parameters, the maximum yield of oleanolic acid obtained experimentally (1.74% dry weight of root) was found to be very close to its predicted value of 1.69% dry weight of root. The mathematical model developed was found to fit well with the experimental data of oleanolic acid extraction.  相似文献   

4.
Melon collapse caused by the heat-tolerant soil-borne fungus Monosporascus cannonballus is not controlled by current solarization technology applied to large soil volumes because the temperatures achieved are not high enough to kill the pathogen's ascospores. The efficacy of improved solarization achieved by mulching a shallow layer of growth medium in containers was studied in terms of disease control and yield increase over two growing seasons. Compared to solarization of a regular container, solarization of a shallow layer (5–6 cm) of growth medium resulted in a 3–5°C elevation in maximal temperature at a depth of 3 cm, and in a 7–10°C increases at the bottom of the shallow layer. This led to a higher disease reduction and higher yields in the 1996 experiment. In 1997, both methods of solarization were highly effective. Yield was highly correlated with disease reduction in both experiments. In the 1997 experiment, ascospore viability declined faster in the shallow container treatment than in the regular container. This study demonstrates the potential of an additional approach for improving solarization of containerized plant growth medium and improving its reliability, with the aim of controlling heat-tolerant pathogens.  相似文献   

5.
Studies on the mechanisms of resistance of some rice cultivars and the weed, Leersia hexandra, to Nephotettix malayanus indicated low survival and popu;ation growth of the insect on resistant cultivars. Tests on feeding behaviour indicated that more feeding punctures were made on resistant than on susceptible cultivars. The amount of honeydew excreted was not related to the levels of resistance. Honeydew excreted on resistant cultivars was acidic (pH 5·08–6·92) and on susceptible L. hexandra, basic (pH 7·56). On the basis of the quality of honeydew excreted, N. malayanus was considered to be predominantly a xylem feeder. A test on the serial transmission of the rice tungro virus (RTV) showed that N. malayanus transmitted the virus for only one day after feeding acquisition. N. virescens was a more efficient vector of RTV than N. malayanus. N. malayanus prefers to feed on L. hexandra rather than on the rice cultivars tested.  相似文献   

6.
Experiments at Bharatpur, Pantnagar, Berhampur, Mohanpur, New Delhi, S.K. Nagar, Kangra and Sriganganagar, India were sown with oilseed Brassica cultivars Varuna and an important cultivar for the area on 10 dates at weekly intervals. Data of experiments conducted previously at Hisar and Ludhiana as available in reports were also used for the study. Mustard aphid (Lipaphis erysimi) appearance on inflorescences of the plants was positively correlated to a maximum temperature between 20–29 °C in the preceding week and also to a morning relative humidity (RH) >92% and daily mean RH of >75%. Long hours of leaf wetness and minimum temperature >5 °C also favoured aphid infestation. Regional and cultivar specific models were developed to predict the crop age at which the mustard aphid first appears on the crop, the peak number of aphids and the crop age at peak number at least 1 week ahead of first appearance of the pest on the crop. These will allow growers to apply insecticides in a more timely and effective manner. Here we report only the models that were found effective based on validation in the 2 years.  相似文献   

7.
Globe artichoke (Cynara scolymus L.) and cultivated cardoon (C. cardunculus L. var. altilis DC.) are horticulturally important crop plants. These species have potential as biomass and oilseed crops. We field tested, for 3 years, two artichoke and two cardoon cultivars and one wild cardoon (C. cardunculus L. var. sylvestris Lam.) population on the Sicilian plain of Catania (37°27′ N, 15°04′ E, 10 m a.s.l.). On a 3-year average, the dry aboveground biomass resulted about 31 t ha−1 in both cultivated cardoons, 18.8 t ha−1 in wild cardoon, 13.7 t ha−1 in globe artichoke ‘3/10 V.S.’ and 9.9 t ha−1 in globe artichoke ‘374’ F1. The caloric values of aboveground biomass (except for seeds), which was not significantly different among genotypes, ranged between 16 005 and 17 028 KJ kg−1 of dry matter. The cultivated cardoon ‘Gigante di Lucca’ had the greatest grain yield (on 3-year average, 2.6 t ha−1), whereas the two globe artichokes had the lowest yield (on 3-year average, 0.5 t ha−1). Regardless of genotypes and years, the grains contain 20.1% crude protein, 24.4% oil, 18.5% crude fiber and 4.1% ash (dry weight basis). The grains of globe artichokes showed the highest crude protein content (21.6%), whereas those of cardoons the highest oil content (25.2%).  相似文献   

8.
Temperature and photoperiod can be used to simulate soybean (Glycine max [L.] Merr) phenology because they serve as surrogates for complex biochemical pathways leading to the appearance of certain developmental stages at the whole plant level. We developed a soybean phenology model (SOYDEV) which utilizes non-linear temperature and photoperiod functions and separates floral induction and post-induction for simulating time of flowering. This model accurately simulated the dynamics of vegetative development, final node number and the occurrence of major reproductive stages such as flowering (R1), beginning pod (R3), mid-pod elongation (R3.5), beginning seed (R5), and physiological maturity (R7) in a long-term field experiment (6 years) with the semi-determinate soybean cv. NE3001, as well as in a 2-year cultivar × sowing date experiment with 12 (2004) and 8 (2005) cultivars. With cultivar-specific model calibration, root mean square errors (RMSE) of major phenological stages simulated with SOYDEV averaged 1.8 days in the long-term experiment and 3.3 days in the cultivar × sowing date experiment. Data from the cultivar × sowing date experiment were used to develop empirical relationships for estimating key cultivar-specific model parameters from published soybean maturity group ratings (0.8–4.2). Compared to using nine cultivar-specific parameters derived from the full calibration, estimation of model parameters from readily available cultivar information such as maturity group rating only slightly decreased simulation accuracy, resulting in RMSE (across stages and cultivars) values of 3.6–3.8 days. The proposed SOYDEV model may be particularly suitable for practical model applications because of its reduced need for cultivar-specific calibration. Further evaluation of the model is required under a wider range of variety maturity group ratings and environments.  相似文献   

9.
The importance of sowing dates to the development of sorghum ergot (Claviceps africana) was determined at Tlayca, Morelos, Mexico during the rainy seasons of 1998–2000. Annual variation in ergot incidence occurred, with the highest levels in the year 2000. Sowing dates between June 15 and July 14 had the lowest levels of ergot incidence and severity. Temperatures below 15°C 3 weeks before flowering increased ergot incidence. The optimal weather factors for ergot development were a mean day temperature of 25°C, a maximum relative humidity of 96%, a maximum temperature of 28°C, and nighttime relative humidity of 86%.  相似文献   

10.
Wild evening primrose species (Oenothera spp.) native to Argentina, have been suggested as a new crop for irrigated valleys of semi-arid Patagonia. This paper describes patterns of biomass allocation, morphological traits related to stress-tolerance and seed-yield in four species of Oenothera grown in a common garden at three plant densities. Wild and domesticated species are compared. The effect of resource availability on those traits during three phenological stages (vegetative, reproductive and maturity) is described. Native species were characterized by traits related to stress-tolerance (high root allocation and low specific leaf area) during the vegetative stage. This suite of traits resulted in low biomass accumulation and low seed-yield. The domesticated O. biennis was characterized by a combination of traits related to stress-tolerance (low specific leaf area) and high productivity (high leaf allocation and leaf area ratio and low root allocation). Domesticated species accumulated more biomass than natives. Total biomass and total non-structural carbohydrates present in roots were positively correlated to seed-yield.Oenothera biennis showed the highest seed-yield, although this species showed yield instability in response to changes in the environmental quality. No changes in seed-yield in response to plant density were recorded for either O. lamarckiana or native species. Oenothera biennis showed an optimum density of 20 plants m−2 and yielded 260 g m−2, a seed-yield similar to that reported in other countries. Low seed-yield of native species is major drawback that must be overcome. Improving seed-yield in these species could be possible by selection oriented to increase total biomass. Since no detrimental effect of density was found in O. lamarckiana and natives, a higher plant density might increase yield production per unit area.  相似文献   

11.
The many recent dry-grind plants that convert corn to ethanol are a potential source of substantial amounts of corn oil, if an economical method of separating it can be developed. Oil separation from corn germ by aqueous extraction (AE) was studied. Batches of 5–20% germ in a buffer solution were preheated in a pressure cooker, ground in a blender or colloid mill, churned in an incubator/shaker and centrifuged to separate a free oil fraction. The highest oil yields were obtained when the germ mass fraction was between 0.1 and 0.16. Addition of an enzyme solution to the ground germ suspension prior to churning, aqueous enzymatic extraction (AEE) gave an oil yield twice as high as the AE yield, carried out using similar conditions. Both types of extraction produced the most oil after a 122 °C cook followed by churning at 160 rpm and 70 °C. Oil yield increased linearly with dispersion loading, from 0.5 up to 1.0 g/cm2 based on beaker cross-section (0.09–0.12 germ mass fraction). Over a several month period the germ used for the extractions became more difficult to extract, despite storage at 4 °C.  相似文献   

12.
Evening primrose (Oenothera spp.) has the potential to become an alternative oilseed crop in Patagonia, Argentina. This paper describes and compares phenology and allocation patterns of four wild accessions of Oenothera grown in a common garden, under non-limiting conditions. Our objective was to identify useful traits to shorten the domestication process. Accessions differed in the duration of the vegetative growth phase, which was negatively correlated to seed production per plant (reproductive output). Fruit set ranged between 70% and 95%, and did not differ among accessions. Differences found in the rate of capsule production did not explain the observed disparity in the number of fruits per plant. Reproductive output was mainly affected by the number of fruits per plant, vegetative biomass, and the proportion between seeds and total biomass (reproductive effort). Individual seed mass did not affect total seed production per plant. Seed-oil content was similar to that of domesticated species of evening primrose, but the content of gamma-linolenic acid was far too low (<2%) in comparison to the minimum acceptable standard necessary for seed commercialization (9%). Oenothera wild accessions are prone to seed losses by shattering. We concluded that short vegetative growth phase and high vegetative biomass would be useful traits for selection in breeding programs. Fruit shattering and low gamma-linolenic acid content are the main drawbacks that should be overcome to facilitate the domestication of one of these wild accessions.  相似文献   

13.
S. Yücel 《Crop Protection》1995,14(8):653-655
Field trials conducted in the pepper growing area ( çel/Turkey) showed that solarization alone and combined with a reduced dose of methyl bromide (40 g/m2), were effective in controlling crown blight disease caused by Phytophthora capsici. Solarization was achieved by covering plots with a clear polyethylene sheet, 0.03 mm thick for 8 weeks. The temperature reached 47 °C and 35 °C at 5 cm and 30 cm soil depth, respectively, an average of 3–8 °C higher than those at equivalent depths in the untreated plots. The average incidence of the disease in solarization plus a reduced dose of methyl bromide, the recommended dose of methyl bromide, solarized and untreated plots in 1991 and 1992 were 17.6 and 13.3%; 20.8 and 16.8%; 24.1 and 19.7%; 39.8 and 42.9%, respectively. All treatments significantly reduced disease incidence.  相似文献   

14.
Organically grown carrots (Daucus carota L.) have a relatively short storage and shelf life, mainly because chemical measures cannot be implemented to control plant pathogens. Laboratory experiments demonstrated that steam treatments substantially reduced decay of stored organically grown carrots. Prior to being packaged, winter carrots were exposed to 3 s of steam. After 60 days of storage at 0.5°C plus an additional week at shelf conditions (20°C), 2% of the carrots were decayed, as opposed to 23% in the nontreated control. When carrot was inoculated with the fungi Alternaria alternata, [(Fr. : Fr.) Keissler] A. radicina (Meier) and Sclerotinia sclerotiorum [(Lib.) De Bary], percentages of decay, after similar periods of storage and shelf life, were 5% for steam-treated carrot and 65% for the nontreated control. In semi-commercial experiments carrots were treated with steam during the sorting process, and similar results were obtained. Higher decay was found in spring-grown carrots because of the presence of the bacterium Erwinia carotovora.sub. sp. carotovora  相似文献   

15.
Effects of photoperiod on phasic development, leaf appearance and seed growth in two cultivars of quinoa (Chenopodium quinoa Willd.), and of photoperiod × temperature interactions on seed growth in one cultivar, were examined. The cultivars were Kanckolla (an early-flowering cultivar from the Andean plateau in Southern Peru) and Blanca de Junín (an intermediate flowering cultivar from the tropical valleys of central Peru). The main objectives were to establish which developmental phases are sensitive to photoperiod and whether conditions during a particular phase had delayed effects on subsequent development. Plants were grown in naturally lit growth cabinets and photoperiods were given as 10 h of natural daylight followed by extensions with low intensity artificial light giving either a short (SD, 10.25 h) or long (LD, 14 or 16 h) photoperiod. Treatments were constant (SD or LD) photoperiods or involved transfers between photoperiods at different developmental stages. A quantitative SD response was observed for time to anthesis and total number of leaves, and more than 50% of leaf primordia were formed after floral initiation. With transfers effected during the reproductive phase, the maximum number of leaf primordia, total number of leaves and time to anthesis varied by up to 9%, 33% and 24%, respectively, in relation to controls under constant SD; and by up to 8%, 39% and 12%, respectively, in relation to controls under constant LD. Photoperiods applied after leaf primordia initiation had ceased affected duration of the reproductive phase and total number of leaves through effects on the proportion of primordia that remained unexpanded (range 7–33%). Plants grown in SD until anthesis produced seed, measured 66 days after anthesis, four-fold larger in diameter than seed on plants always grown in LD. Seed diameter was also reduced by 24% by LD applied after anthesis, and by 14% by high temperature (28°C cf. 21°C), but the combination of high temperature with LD gave the greatest inhibition of seed growth (73%). Clearly, photoperiod had strong effects on all stages of plant reproduction and often acted indirectly, as shown by delayed responses expressed in later phases of development.  相似文献   

16.
Sheila M. Fitzpatrick   《Crop Protection》2007,26(12):1810-1816
Flooding for several days in late summer or early fall is reported to control larvae of the cranberry girdler, Chrysoteuchia topiaria (Zeller) (Lepidoptera: Pyralidae), which feed on roots of cranberry, Vaccinium macrocarpon Aiton (Ericales: Ericaceae). During flooding, larvae float to the surface or remain submerged. Floating larvae are vulnerable to bird predation, but the fate of submerged larvae has not been studied. The factorially designed laboratory experiments reported here examined survival of submerged cranberry girdler larvae at water temperatures of 10, 15 or 20 °C, and flood durations of 24, 48 or 72 h. These conditions are characteristic of floods applied to western Canadian cranberry farms. In the first year of the study, more submerged larvae survived at 10 °C than at 15 or 20 °C, and more survived 24-h submersion than 48- or 72-h submersion; there was no difference between survival at 15 and 20 °C or 48- and 72-h submersion. In the second year of the study, when there were no 10 °C treatments, more submerged larvae survived at 15 than at 20 °C, and more survived 24-h submersion than 72-h submersion; survival after 48 h was not significantly different from survival after 24 or 72 h. In both years, there was no interaction effect of water temperature and duration of submersion: survival of submerged larvae decreased with longer flood durations and higher temperatures. Dissolved oxygen concentrations before submersion ranged from 5.8±0.1 to 6.3±0.2 ppm in the first year, and 5.5±0.1 to 5.7±0.1 ppm in the second. After submersion, dissolved oxygen concentrations in cups with larvae were approximately 0.5 ppm lower than in cups without larvae, suggesting that larvae continued to respire and use oxygen for some time after submersion. Results of the experiments are used to improve guidelines for flooding to control cranberry girdler larvae.  相似文献   

17.
Soybean is the main rainfed crop in a wide range of latitudes and sowing dates of the Argentine Pampas. It is sown alone or as a second crop after other winter and summer crops. Modelling approaches have proved to be helpful in the decision making process. The on-farm evaluation of CROPGRO is rather difficult since input data are scarce and frequently of worse quality than those from experimental works. Moreover, CROPGRO simulation of water dynamic processes and their relation with biomass production has not been comprehensively evaluated in soybean crops. The aims of this study were (i) to evaluate the CROPGRO-soybean performance, with emphasis on water demand and supply and biomass production under water limited conditions, (ii) to generate a revised CROPGRO model improving those aspects, and (iii) to compare simulations outputs using the original and the revised CROPGRO models, with on-farm crop data set. In the revised model, we multiplied potential evapotranspiration by 1–1.22 when LAI increased from 0 to ≥4.0. We set a root extension rate of 4.0 cm/thermal day and a maximum rooting depth of 2.5 m. Finally, we included a nonlinear equation to simulate the relationship between relative transpiration and relative gross photosynthesis. The ability of the revised CROPGRO-soybean to simulate water content depletion and biomass production was tested against several experiments with an imposed drought period. We also calibrated cultivar parameters using “ad hoc” tests in a range of environments (combinations of sowing dates and locations). The models were evaluated with data from 155 commercial farms. V (%) (root mean square error as percentage of the observed mean) for the total cycle length, vegetative period, and reproductive phase simulations were 7, 13 and 15%, respectively. The revised CROPGRO was more accurate in simulating crop yield, biomass, harvest index and yield numeric components. V (%) values ranged from 11 to 17% (revised version) and from 13 to 22% (original version). Besides, V (%) values for yield were 16% with the revised model versus 32% with the original one, considering only paddocks with higher water stress level. The robust prediction of phenology, biomass and yield components obtained with the revised model across different environmental conditions, support its use in the decision making process of the soybean crop at the farm scale.  相似文献   

18.
Z. Basky 《Crop Protection》1993,12(8):605-609
A yellow water pan trap was used to collect Diuraphis noxia (Mordvilko) in Central Hungary in 1989. In 1990 a Rothamsted-type suction trap collected 31 individuals. A D. noxia infestation was found in an autumn-sown wheat field in October 1990. The D. noxia population that overwintered was holocyclic. The life-span of fundatrices was 43.2 days at 18–22°C. The number of nymphs produced per fundatrix was 46.6. Average progeny numbers of first-generation apterae and alatae were 29.4 and 21.4, respectively. Second-generation apterae produced an average of 48.8 nymphs; 35.9% of nymphs were alatiform. The D. noxia population reached its peak on 3 July in the field, at which time the mean number of individuals per wheat plant was 3953.6. By 20 July, the wheat plants had matured and the D. noxia colonies had disappeared from the wheat.  相似文献   

19.
Artificial grassland establishment has been implemented in the alpine region of Qinghai–Tibetan Plateau in China as a mitigation tool against grassland degradation, one of the major environmental problems in this region. We hypothesized that both grassland degradation and artificial restoration may alter the reproductive modes of the alpine vegetation at the levels of individual species as well as plant functional groups. By investigating a long-term field study of grassland degradation and artificial restoration experiments, we found that alpine plants can maintain a highly plastic relationship between sexual and asexual reproduction, that is, the alpine plants in degraded grasslands increased their efforts towards sexual reproduction while those in artificially restored grasslands promoted their efforts in vegetative reproduction with in the year after restoration. The high reproductive plasticity of the alpine plants can be regulated through a number of mechanisms, which include changing proportion of clonal species in the plant composition, altering number ratio of sexual and vegetative propagules, shifting biomass allocation for sexual and vegetative reproduction at both individual species and functional group levels. These conclusions demonstrate how crucial it is to consider manipulation of reproductive modes needed to restore the structure and stability of degraded alpine grasslands.  相似文献   

20.
A 3 years field trial examined the effect of newly and previously applied lime on the growth and yield of two near-isogenic wheat genotypes differing only in aluminium (Al) tolerance (Triticum aestivum L. Al-sensitive line ES8 and Al-tolerant line ET8), and barley (Hordeum vulgare cv. Mundak) on an acid soil (pHCaCl2 4.6 in 0–10 cm and pH 4.1–4.3 in 10–40 cm) in the medium rainfall region of Western Australia. The trial consisted of four lime treatments: (i) no lime control; (ii) surface liming at 1.5 t ha−1 in 1999; (iii) surface liming at 2.5 t ha−1 in 1984; (iv) liming in 1984 and re-liming in 1999. Wheat crops were grown in 1999 and 2001, and barley was grown in 2000.

Liming in 1984 increased the pH in both topsoil and subsoil and decreased toxic Al in the subsoil. Liming in 1999 largely increased soil pH in the 0–10 cm in previously unlimed and limed plots, but only slightly increased the pH in 10–20 cm 2 years after application. In 1999, there was an overall 14% grain yield increase by growing ET8, mostly due to much better performance (41%) of ET8 over ES8 in the treatment with surface liming in 1999. In 2001, ET8 had yield 24% higher in the no lime control and 14% higher in the treatment with liming in 1999 compared with ES8. While both genotypes had similar root length density in the topsoil, root length density in acid subsoil was 22–160% higher for ET8 than for ES8. Wheat genotypes produced 23–24% higher yield due to the liming in 1984 compared to the no lime control. In 2000 season, shoot biomass of barley increased by 45–70% in the limed treatments compared with the no lime control. Liming at 2.5 t ha−1 in 1984 or liming at 1.5 t ha−1 in 1999 increased yield by 25%. Liming in 1984 and re-liming in 1999 increased the yield by over 50%. The results suggest that surface liming can ameliorate subsoil acidity as measured 15–17 years after application, and that growing an Al-tolerant crop in combination with surface liming provides a good strategy to combat subsoil acidity. The genotypic variation in response to liming appears to result from the difference in the sensitivity of root proliferation to low pH and high Al.  相似文献   


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