Scientia Agricultura Sinica

Construction of Triticum aestium L. Glycogen Synthase Kinase (TaGSK1) Expression Vector and Its Prokaryotic Expression

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Scientia Agricultura Sinica. 2004, 37(11): 1593-1597 .

Abstract ( 890 )

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Utilizing plasmid pDT-23 containing Tagsk1 as template, Tagsk1 was amplified and sequenced, and then ligased it into prokaryotic expression vector pBV221, then the pBV221-gsk1 was obtained. Tagsk1 expressed 43.5kD protein both in E.coli DH5α and BL21 whose expression amount were 8% and 10.8% respectively. Tagsk1 improved the transformants' salt tolerance greatly at the concentration of 0.31 mol·L-1 NaCl.

Improvement Efficiency of Modified S1-HS Alternant Recurrent Selection in Maize Population ZZ4

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Scientia Agricultura Sinica. 2004, 37(11): 1598-1603 .

Abstract ( 898 )

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Four cycles of modified S1-HS (MS1-HS) alternant recurrent selection to improve grain yield of ZZ4 maize (Zea mays L.) population have been completed in northern China. In 2001, 30 NCⅡ testcrosses and 11 parents (including six testing lines and five populations for each cycle) were tested at four locations. Analysis of variance indicated that significant progress（p﹤0.05）was achieved for major agronomic traits of populations and testcrosses. MS1-HS alternant recurrent selection was effective for increasing grain yield of testcrosses, heterosis and general combining ability. The average yield increase of testcrosses to MS1-HS alternant recurrent selection in ZZ4 was 6.7%-8.1% per cycle. Increased yield of testcrosses was accompanied with increased heterosis. The average gain for mid-parent yield heterosis of testcrosses to MS1-HS alternant recurrent selection in ZZ4 was 211 -248 kg·ha-1per cycle. The GCA of grain yield and ear traits all increased cycle by cycle. The MS1-HS alternant recurrent selection seemed to be less effective to improve special combining ability (SCA). ZZ4 and Huangzao4 or Dan340 lines may be the most efficient herterosis pattern after comparing the yield of hybrids and heterosis between improved population and the 6 testing lines.

Genetic Variation of Popcorn Inbreds and Their Genetic Relationship with Normal Corn Inbreds Revealed by SSR Markers

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Scientia Agricultura Sinica. 2004, 37(11): 1604-1160 .

Abstract ( 828 )

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One hundred and thirteen SSR markers with polymorphism were used to study the genetic diversity of 26 popcorn inbred lines derived from 8 sources, and their genetic relationship with 20 normal maize inbred lines representing 6 different heterotic groups. Among the 26 popcorn inbred lines, the average number of alleles per SSR locus was 2.66 with a range of 1 to 3, the polymorphism information content (PIC) for the SSR loci varied from 0.068-0.217, and the genetic distance ranged from 0.148-0.524 with an average of 0.357. The cluster analysis showed that all the inbred lines could be classified into two distinct clusters, popcorn and normal maize. The 26 popcorn inbred lines were divided into 8 clusters, with all the parents of elite popcorn crosses being classified into different clusters. The cluster analysis of 20 normal maize inbred lines was accordant with previous studies. Consequently，SSR makers could be used to study the genetic diversity of popcorn inbred lines. The average genetic distance among different clusters of popcorn and normal maize inbred lines were 0.55 to 0.67. To improve popcorn inbreds using normal maize lines in the long run, the genetic relationships should be taken into serious consideration.

Diallel Crossing Analyses of Resistances to Main Diseases in Pepper (Capsicum annuum L.)

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Scientia Agricultura Sinica. 2004, 37(11): 1636-1640 .

Abstract ( 1016 )

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Fifteen capsicum combinations were made with 6 parents by (1/2) n (n-1) diallel crossing. Genetic parameters in the resistance to TMV, CMV, phytophthora blight, bacterial spot of these combinations were studied by Hayman. The results indicated that the resistances to TMV, CMV and bacterial spot conformed genetically to the "additive-dominant" model but the resistance to phytophthora blight did not and significant epistatic dominance effect existed in it. F1 hybrid's resistance to CMV was controlled by homozygous dominant gene(s), but resistance to bacterial spot by heterozygous one(s). There were little, or no sum of dominant effect and genomes controlling the dominant expression of F1 hybrids in its phytophthora blight resistance.

Genetic Diversity of Rhizobia Isolated from Pueraria spp.in Sichuan, China

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Scientia Agricultura Sinica. 2004, 37(11): 1641-1646 .

Abstract ( 1130 )

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Twenty-three rhizobial strains isolated from Pueraria spp. in different sites of Sichuan province were studied by using AFLP, BOXAIR-PCR and 23S rDNA PCR-RFLP techniques. The results showed that genetic diversity among these rhizobia was existed. The analysis of AFLP revealed that, there were seven AFLP genotypes among these rhizobial strains; and BOXAIR-PCR suggested that, there were five genotypes existed. The results from 23S rDNA PCR-RFLP analysis revealed that, from the phylogeny point of view, these rhizobia belong to Mesorhizobium sp. and Bradyrhizobium sp., and however, most of them were different from the type strains of the related genera, which indicated that maybe there are putative new species existed.

Study on the Soil Erodibility Based on the Soil Particle-size

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Scientia Agricultura Sinica. 2004, 37(11): 1647-1653 .

Abstract ( 872 )

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Soil erodibility is an essential parameter in the model for predicting soil erosion and also the basis for quantificative study of soil erodibility. Based on the data of soil particle-size distribution, soil map, soil physical and chemical properties in the Second Soil Investigation of Hebei Province. The veracity of the modified logistic growth model with two parameters and the conversion of soil texture scheme from the Katschinski to the USDA were studied, the soil erodible K value was calculated using the formula method and the K value map well registered with the topographic map was made, in which accurate geographic position could be located. Meanwhile, the area with soil erodible K value between 0.25 and 4.0, the erosion and relative erosion soil was about 58.6% of the total area in this province. Applications of the K value and map were also discussed.

The Relationship Between Differential Gene Expression Patterns at Rosette Stages and Heterosis in Brassica campestris and Their Hybrids

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Scientia Agricultura Sinica. 2004, 37(11): 1654- .

Abstract ( 955 )

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With the inbred line 'Aijiaohuang 97-3-2', 'Huangxinwu 003-27', 'Shanghaiqing 98-4-2' of Chinese cabbage-pak-choi (Brassica campestris L. ssp. chinensis Makino; syn. B. rapa L. ssp. chinensis) ,the inbred line 'Baimanjing 001-24' of turnip [B. campestris L. ssp. rapifera (Matzg.) Sinsk; syn. B. rapa L. ssp. rapifera], the inbred line 'Huangyacai 97-8-6' of Chinese cabbage-pe-tsai(B. campestris L. ssp. pekinensis Olsson; syn. B. rapa L. ssp. pekinensis) and 6 hybrids as experimental material. The relationship between differential gene expression patterns at rosette stage and heterosis of biologic yield component traits in the hybrids and their parents was analyzed by using cDNA-AFLP. Four types of differential gene expression patterns were detected between hybrids and their parents: UNF1 bands were observed only in F1 not in parents; ABF1 bands were observed in both parents but not in F1; UNP bands were observed only in one parent but not in F1 and another parent; DMP bands were observed in one parent and F1 not in another parent. Analysis results showed that ABF1 was significantly correlated with heterosis in leaf number, UNP was significantly correlated with heterosis in height of plant. These results indicated that differential expressed genes might play an important role in heterosis.

Effect of Carboxymethyl Chitosan on Chilling Tolerance in Cucumber Seedlings

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Scientia Agricultura Sinica. 2004, 37(11): 1660-1665 .

Abstract ( 981 )

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Carboxymethyl chitosan at 0 (CK), 1/1500, 1/1000, 1/500 and 1/100 (w/v) was sprayed on cucumber seedlings on two leaves stage respectively, and then the cucumber seedlings were stressed under low temperature at 6±1℃ for 5 days, in order to study influence of carboxymethyl chitosan on chilling tolerance of the cucumber seedlings. The main results were as follows: Under low temperature stress, the cucumber seedlings sprayed with carboxymethy chitosan of favorable concentration obtained lower chilling injury index and MDA content, higher activities of protein enzyme (SOD, CAT and POD), root activity and content of Vc, soluble sugar, proline and chlorophyll compared with control. After low temperature stress, the cucumber seedlings were transferred to greenhouse for 5 days. Increase of dry matter , photosynthetic intensity and carboxlyation efficiency of the cucumber seedlings treated with favorable concentration of carboxymethyl chitosan were much higher than that of control. This fully explained that carboxymethyl chitosan in favorable concentration evidently improved chilling tolerance in cucumber seedlings.

Studies on the Flora of the Genus Malus Mill. in Hengduan Mountainous Region

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Scientia Agricultura Sinica. 2004, 37(11): 1666-1671 .

Abstract ( 1124 )

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Both the shrinkage of ancient Mediterranean Sea and the ridge between the Himalayas－Hengduan mountain have an important effect on the development of the flora of the Malus Mill. The origin and development of the flora of the Malus Mill. in Hengduanshan mountain were discussed with the theories and methods of systematics and phytogeography. The result indicated that the small fruit types of M.laosensis Chev. was transmitted to Hengduan mountainous district from the southern part of Yunnan by river valley. During this process, Ser. yunnanense Rehd. was evolved from permanent calyx, and Ser. kansuensis(Batal.)Schneid. was evolved from decalyx , too. The evolving features of the flora of the Malus Mill. in Hengduan mountain were: (1) the long-lasting history; (2) the many types; and (3) the differential among types. Furthermore, the flora of the Malus Mill. in Hengduan mountain which had the distinctive evolution center and the radiating distribution, demonstrates the flora of the genus Malus Mill. in Hengduan mountainous region had a rich types, but it is not the area where origin species don't appear. So it is an evolution center of the Malus Mill., not an origin center.

A Review on the Control of Patulin in Apple Juice

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Scientia Agricultura Sinica. 2004, 37(11): 1672-1677 .

Abstract ( 940 )

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Recent development in techniques of controlling patulin in apple juice was reviewed. Spoilage of apples by patulin producer (Penicillium expansum) was the main source of patulin in apple juice. On the basis of characteristics of patulin producers, storing apples at proper temperature（4℃）and in proper package material (polyethylene, PE), and shortening the storage period could prohibit the production of patulin in apple. Effective methods in decreasing patulin contents in apple juice were selecting proper apple varieties, washing fruits and discarding rotten apples before squeezing, clarifying and absorbing juice during juice process, and treating clarified juice with microwave, irradiation, reducers, and food preservatives.

Protection of Rabbit Hemorrhagic Disease Virus by Immunization with the Recombinant Capsid Protein Expressed in E. coli

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Scientia Agricultura Sinica. 2004, 37(11): 1677-1681 .

Abstract ( 851 )

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The immunogenicity of the recombinant rabbit hemorrhagic disease virus (RHDV) capsid protein (VP60) expressed in E. coli was investigated. Thirty-four clean rabbits were randomly divided into 3 groups and respective subcutaneously injected twice, with 7 days interval, using adjuvant (8 rabbits), the recombinant VP60 (8 rabbits) and VP60 mixed with adjuvant (18 rabbits). The dosage of VP60 protein was 400μg per injection. Titer of the antibody raised by VP60 protein combined adjuvant was much higher than that of VP60 protein only at the 7th day after second injection (ELISA 1∶64 000 vs 1∶4 000 / HI 1∶128 vs 1∶16). The result indicated that adjuvant could accelerate the production of antibody. The immunized animals were challenged with highly virulent NJ85 isolate of RHDV. The mortality rates were 100% (8/8) for the adjuvant control and recombinant VP60 groups. In the meanwhile, the protective rate was 100% (18/18) for VP60 combined with adjuvant group. The death caused by RHDV infection was confirmed by the evidences that HA titer of liver tissue in dead rabbits was over 1∶512 while less than 1∶2 in surviving rabbits, and no bacteria staining in liver tissues smear as well as no bacteria growth in culture. Eight hundred domestic rabbits in rabbit farm immunized with the recombinant subunit vaccine to RHD and the occurrence of RHD and harmful effects due to the vaccination were not observed. Additionally, it was also confirmed that the recombinant E. coli could keep stability in the process of storing, restoring, culture, induced expression and digestion of recombinant plasmid.

Comparative Study on the Infectivity and Spore Surface Protein of Nosema bombycis and Its Morphological Variant Strain

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Scientia Agricultura Sinica. 2004, 37(11): 1682-1698 .

Abstract ( 1062 )

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A new morphological variant strain was produced by infecting the mulberry looper, Hemerophila atrilineata [Phthonandria atrilineata], with Nosema bombycis successively for 24 times, and named 24Nbh. Comparative studies on morphology, infectivity and spore surface protein were conducted. 24Nbh was short and wide, and had a significant difference (P<0.01) over the Nb spores. The infectivity tests conducted on second instar silkworm larvae showed that IC50 of 24Nbh was 1.98×104 spores/ml and of Nb was 1.72×103 spores/ml, thus indicating that the infectivity of Nb decreased 11.5 times after multiplying in mulberry looper for 24 times. The IC50 of spores from silkworm infected with 24Nbh was 6.9 time less than Nb, showing that the infectivity of 24Nbh spores rejuvenated very fast when reinfected to silkworms, furthermore, the length and width of such spore was larger (P<0.01) than 24Nbh and smaller (P<0.05) than Nb. The SDS-PAGE profiles of Nb and 24Nbh were generally the same, distinct 4 proteins of 12 kD, 17 kD, 30 kD, 33 kD were obtained with differences in quantity. When 120 μg of protein was used for 2D-PAGE, five suspected different proteins with difference in quantity was observed. These results demonstrate that these differential proteins maybe associated with variation in infectivity.

Genetic Diversity and Classification of Ecotypes of Eulaliopsis binata via Morphological Traits and AFLP Markers

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Scientia Agricultura Sinica. 2004, 37(11): 1699-1704 .

Abstract ( 962 )

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AFLP markers and morphological observation were used to identify the ecotypes of Eulaliopsis binata, which was reported as an apomictic species in Poaceae. The result showed that there is a large diversity among different ecotypes but a little within each population. By cluster analysis based on AFLP data, four ecotypes were identified as follows: slender-leaf ecotype (Hubei), deep-green-leaf ecotype（Guangxi）, red-haulm ecotype (Shaanxi) and wide-leaf ecotype (Henan). The utilizations of AFLP markers in classification and further investigation of apomictic plants were discussed as well.

Root Cell Plasmalemma of Upland Rice and Wetland Rice Related to Nitrogen Uptake

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Scientia Agricultura Sinica. 2004, 37(11): 1705-1708 .

Abstract ( 862 )

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The H+-ATPase activity and its H+-pumping capacity of plasmalemma isolated from a conventional Japonica rice (Wuyujing 3), a conventional Indica rice (Yangdao 6), and an upland rice (Brazil upland rice), were measured, respectively. Combined with the results of nitrate uptake kinetic and effects of ammonium on nitrate uptake of 3 varieties, the relationships between parameters was studied. The results show that the H+-ATPase activities of 3 varieties are in consistent with H+-pumping capacity. The H+-ATPase activities and H+-pumping capacities were in the following order: Brazil upland rice > Wuyujing 3 > Yangdao 6. For nitrate uptake the Vmax of Brazil upland rice was significantly higher than those of other genotypes, and was less affected by ammonium. Ammonium has the largest repressive effect on the nitrate uptake by Wuyujing 3 than on that of other 2 varieties. The effect of ammonium on nitrate uptake may be due to the decreasing membrane potential, which could descend the so-called proton-driving-force, and repressing synthesis of nitrate-carrier in plasmalemma. However, ammonium has no effect on the affinity of carrier to nitrate.

Application of Near Infrared Transmittance Spectroscopy (NITS) to the Determination of Amylose Content of Rice Grain

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Scientia Agricultura Sinica. 2004, 37(11): 1709-1712 .

Abstract ( 1036 )

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One hundred and twenty-four samples of small amount of rice grain were scanned by Foss Tecator Infratec 1255, and their amylose contents were determined by chemistry method. With the WINISI calibration maker software, several mathematics treatments to the sample spectra and several different regression methods were adopted to optimize a good calibration equation for determination of amylose content in small amount of rice grain. The standard error of calibration (SEC), standard error of cross-validation (SECV) and regression squared (RSQ) of the calibration selected were 1.489, 1.761 and 0.885.

Variation of Polyphenol Oxidase Activity in Common Wheat Varieties

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Scientia Agricultura Sinica. 2004, 37(11): 1713-1717 .

Abstract ( 1019 )

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Taking catechol as substrate, polyphenol oxidase (PPO) activities in two hundred common wheat varieties were assayed by means of full-seed steeped in distilled water to extract PPO and measuring PPO activities by spectrophotometric methods. The results indicated that (1) frequency of varieties at different ranges of polyphenol oxidase activity showed skewed curve distribution, and top value trended to low polyphenol oxidase activity aside. (2) The variation of PPO activity was related to grain color and vitreousness. In red wheat, the rates of varieties with PPO activity above 100 AU·min-1·g-1 and 200.0 AU·min-1·g-1 were 31.82% and 11.63%, respectively. The variation of white wheat varieties was smaller than that of red wheat. The peak of PPO activity distribution curve in white wheat was close to 28.3 AU·min-1·g-1, and the rate of varieties with PPO activity above 100 AU·min-1·g-1 and 200 AU·min-1·g-1 were 10.40% and 0.06%, respectively. Generally, white wheat was significantly lower than those of red wheat in mean PPO activity and variety numbers with high PPO activity. (3) There was a high rate of low PPO activity varieties in white and chalky or half-vitreous wheat. (4) The variation among the Chinese commercial popular varieties in PPO activity was significant. Many white grain varieties from Huanghuai Wheat-growing Region had lower PPO activity (20～50　AU·min-1·g-1).

Studies on the Relationship of Chlorophyll Fluorescence Characters and Drought Tolerance in Seedling of Sugarcane Under Water Stress

Scientia Agricultura Sinica. 2004, 37(11): 1718-1721 .

Abstract ( 1563 )

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The relationship of drought tolerance and chlorophyll fluorescence characters during water stress in seedling of sugarcane was stuided by using modulated chlorophyll fluorometer. The results indicated that Fv/Fm, Fv/Fo, Yield, Rfd values decreased gradually under water stress. With water stress intensifying, Fv/Fm, Fv/Fo, Yield, Rfd value were decreased depending on the genotypes. The decrease of these chlorophyll fluorescence parameters was closely related to drought tolerance of sugarcane varieties. The possibility of determining the drought resistance in sugarcane using chlorophyll fluorescence characters was studied.

Response of CO2 Emissions to the Change of Major Environmental Factors in Temperate Grassland Ecosystem

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Scientia Agricultura Sinica. 2004, 37(11): 1722-1727 .

Abstract ( 861 )

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Using static dark enclosed chamber technique, the fluxes of CO2 from temperate grassland such as meadow, Leymus chinensis grassland and Stipa grandis grassland and their major environmental factors were measured in Xilin River Basin of Inner Mongolia under the abnormally dry circumstances from June to September in 2001（rainfall was less than 1/6 of that in historical normal years）. Then the correlation between the emissions of CO2 and major environmental factors were studied. The results showed that there was a little or no correlation between the monthly fluctuation of the emissions of CO2 from grassland and air temperature and topsoil temperature during the period of rapid growth of grassland, however the daily variation of CO2 flux was significantly positively correlated with the earth's surface temperature and air temperature. And the relation between the emissions of CO2 and soil temperatures at the depth of 5 cm and 10 cm was not obvious. As for the response of the fluxes of CO2 to annual precipitation, the average emissions of CO2 dropped off from 268.7, 211.6 to 181.4 mg?m-2?h-1 in meadow, Leymus chinensis grassland and Stipa grandis grassland, respectively. That meant precipitation was an important environmental factor influencing the fluxes of CO2 from grassland. It was also found that there was a close and positive correlation between the emission of CO2 and other environmental factors such as soil water content, organic content and total nitrogen content in different soil layers.

Comparison of PCR, DIA and Pathogenicity Assay for Detection of Xanthomonas axonopodis pv. citri, the Causal Agent of Citrus Bacterial Canker Disease

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Scientia Agricultura Sinica. 2004, 37(11): 1728-1732 .

Abstract ( 1077 )

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Polymerase chain reaction (PCR) and newly designed primers, JYF5/JYR5, were tested for selective detection of Xanthomonas axonopodis pv. citri (Xac). The efficiency and reliability of PCR detection method were compared with dot immunobinding assay (DIA) and classical pathogenicity test techniques for detecting Xac in suspensions of pure cells and extracts of citrus samples. Detection limit of PCR was 10 cells or 1.56pg of target DNA per reaction, the sensitivity of PCR assay is higher than DIA (300 cells or more per sample dot). The detection rate of the three techniques (Pathogenicity test, DIA and PCR assay) for Xac reach 100% for symptomatic citrus sample. Differences among the three techniques were clearly evident when using citrus tissues without symptoms, the detection frequency from the least to the most was pathogenicity test, DIA and PCR. Add 15% glycerol in PCR reaction mix can reduce the effect of inhibiting compounds in sample and avoid false negative of PCR.

The Expression of Bt Toxin Gene Under Different Thermal Treatments

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Scientia Agricultura Sinica. 2004, 37(11): 1733-1737 .

Abstract ( 885 )

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Genetic and expressional stability of Bt toxin gene is crucial for the breeding of insect-resistant transgenic cotton varieties and their commercialization. The impact of different temperature on the expression of Bt toxin gene in R5 generation plants during their development was studied. The results indicated that the time point of when the expression of Bt toxin protein in transgenic insect-resistant cotton plants became lower during the development was affected because different thermal treatments had great impact on the development of transgenic plants and their Bt toxin gene expression level. Under high temperature treatment, the silencing of Bt toxin gene during the developmental stages happened ahead of time, leading to the level of Bt toxin dropped dramatically. This was probably caused by the gene regulation at post-transcriptional level, and the full-length mRNA of Bt toxin gene decreased thereafter. Therefore, it is very important to take measures earlier in practice in order to avoid the loss caused by cotton boll-worm during the high temperature period.

Study on Pepper (Capsicum annuum L.) Virus Disease and Its Distribution in the Guanzhong Area of Shaanxi Province

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Scientia Agricultura Sinica. 2004, 37(11): 1738-1742 .

Abstract ( 1174 )

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By means of immunoelectronmicroscopy and ELISA, 137 pepper leaf samples collected from the Guanzhong area of Shaanxi Province were analyzed. The results showed that, in west part of Guanzhong area, the major viruses infecting pepper are CMV and BBWV at seedling stage, and are PMMV, BBWV, CMV, and ToMV etc. in mature period. In the Guanzhong area of Shaanxi Province, the major viruses infecting pepper in mature period are BBWV, CMV, CVMV, and PMMV. In mature period, the results of 4 representative places are as follows: the major virus infecting pepper in the Weinan and Xingping cities is BBWV; the major virus infecting pepper in Meixian county is BBWV and PMMV; the major virus infecting pepper in Qishan county is BBWV and CMV. The results also indicated that the infecting frequency of major viruses is various with different years.

plication of Canopy Spectral Reflectance in Monitoring Nitrogen Status of Winter Wheat

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Scientia Agricultura Sinica. 2004, 37(11): 1743-1748 .

Abstract ( 896 )

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The objective of this study was to make clear whether remote sensing technology can be used to monitor N status of winter wheat. Results from three field experiments in 1997 to 1999 showed that there was a remarkable effect of N rate on wheat canopy spectral reflectance, especially on the red and infrared bands. Ratio vegetation index（RVI） had a remarkable linear correlation with SPAD value and plant tissue nitrate concentration, which implies that RVI is a good indicator of plant N nutrition.

Molybdenum Efficiency in Winter Wheat Cultivars as Related to Molybdenum Uptake and Distribution

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Scientia Agricultura Sinica. 2004, 37(11): 1749-1753 .

Abstract ( 964 )

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The differences of Mo uptake and distribution in Mo-efficient winter wheat cultivar 97003 and Mo-inefficient winter wheat cultivar 97014 were studied in two treatments. Molybdenum (Mo) was applied at the rate of 0(control) and 0.13 mg·kg-1 to an acid yellow-brown soil (soil available Mo 0.112 mg·kg-1). The results showed that the accumulation of Mo and dry matter in shoots of cultivar 97003 was significantly higher（P＜0.01） than in cultivar 97014 in the entire growth period in control. Cultivar 97003 also had a higher Mo accumulation rates in control than that of cultivar 97014, these disclosed that cultivar 97003 had a higher capacity of Mo accumulation under Mo deficiency. Furthermore Mo was distributed in the upper leaves at stem elongation stage, in spikes at heading stage, in seeds at maturity in cultivar 97003 than in cultivar 97014 under the conditions of Mo deficiency, and Mo concentration in spikes and in seeds of cultivar 97003 in control were found significantly higher than that of cultivar 97014, suggesting that a higher efficient use of Mo under Mo deficiency stress for cultivar 97003. The ability of Mo uptake and use were discussed and it was suggested to be the important physiological basis of Mo efficiency.

The Effects of NaCl Stress on Plant Growth, Chlorophyll Fluorescence Characteristics and Active Oxygen Metabolism in Seedlings of Two Cucumber Cultivars

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Scientia Agricultura Sinica. 2004, 37(11): 1754-1759 .

Abstract ( 936 )

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Two cucumber （Cucumis sativus L.）cultivars，'Jinyan 4' (salt tolerant) and 'Jinlü4' (salt sensitive) were grown in nutrient solutions with three NaCl levels（0，25，50 mmol·L-1）for the investigation of plant growth, chlorophyll fluorescence and active oxygen metabolism in seedling leaves. The results showed that NaCl stress decreased plant growth, chlorophyll content, quantum yield of PSII (ΦPSII)，initial fluorescence yield（Fo）and non-photochemical quenching of fluorescence（NPQ）. The plant growth of 'Jinyan 4' was less affected by salt stress than 'Jinlü4' and the photosynthetic apparatus was less injured by salt stress than 'Jinlü4'. However, photochemical efficiency of PSII (Fv/Fm) was not affected by salt stress. Meanwhile，salt stress significantly increased the activity of ascorbate peroxidase (AsA-POD) and significantly decreased superoxide dismutase (SOD) activity in 'Jinlü4'. Free radical producing rate, and H2O2 and MDA content increased with increasing NaCl levels, however, less H2O2 content and lipid peroxidation were observed in the leaves of 'Jinyan 4' than 'Jinlü4'. It is concluded that higher SOD activity, less H2O2 and MDA content may be involved in higher salt tolerance of 'Jinyan 4'.

Physiological Mechanism of Metabolism of Carbohydrate, Phenols, Free Amino Acid and Endogenous Hormones in Middle Scales of Lilium davidii var. unicolor Bulbs Stored at Low Temperature for Dormancy Release

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Scientia Agricultura Sinica. 2004, 37(11): 1777-1782 .

Abstract ( 1323 )

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Changes in carbohydrate, phenols, free amino acids and endogenous hormones in middle scales of Lilium davidii var. unicolor bulbs stored in moist sawdust for 101 days at 2℃, 6℃ and 10℃, respectively, were studied. Results indicated that starch content and ABA level decreased markedly along with decline of storage temperature and prolonging of duration, and total soluble sugar content，phenols content, GA3 and IAA concentration increased sharply. Notable changes of above substances occurred at earlier phase (34 d). Correlation analysis revealed that increase of amylase activity and PAL activity conduced to increase of total soluble sugar content and phenols content, respectively. As a general tendency, free amino acid content decreased, and arginine content was the highest and its changes were dramatic among all kinds of free amino acids. According to results of stepwise regression analysis and path analysis, it is concluded preliminarily that the metabolism in middle scales may be regulated mainly by endogenous GA3.

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