February 1999, Volume 41 Issue 2

 

          Research Articles
Cloning and Sequencing of the cDNA Encoding for Pokeweed Anti viral Protein (PAP) and Construction of Its Plant Expression Vector
Author: ZHANG Hai-Yan, LIU Gui-Zhen and CHEN Zheng-Hua
Journal of Integrative Plant Biology 1999 41(2)
      
    The total RNA was extracted from the leaves of pokeweed ( Phytolacca americana L. ) plants which had been subcuhured for eight weeks. The first strand of cDNA was synthesized from the total RNA template with oligo(dT)15 primer using MMLV reverse transcriptase. A 0.96 kb cDNA fragment was obtained after 30 PCR amplification cycles with two specific primers. The cDNA fragment was sequenced from two directions after being cloned into pGEM-T Easy Vector. The result showed that the cDNA clone had the entire coding region with the same sequence as the previously published pokeweed anti-viral protein (PAP) cDNA clone. The plant expression vector with the PAP cDNA was constructed, and the work of transferring the PAP cDNA into tobacco and rape to obtain transgenic plants resistant to a broadspectrum of viruses is in progress.
Abstract (Browse 1753)  |  Full Text PDF       
Effect of Ripening, Wounding and Ethylene Treatment on Expression of ACC Oxidase Gene of Peach Tissue
Author: JIN Yong-Feng, ZHANG Yao-Zhou and ZHANG Shang-Long
Journal of Integrative Plant Biology 1999 41(2)
      
    RNA-based PCR amplification and Southern blotting of ACC oxidase cDNAs from peach ( Prunus persica L. ) fruits indicated that ACC oxidase mRNA was detected when fruit began to soften at about 75 d after bloom, and its accumulation peaked when the fruit mostly softened (about 1 kg/cm2). ACC oxidase mRNA was undetectable in green fruits and unripe fruits, but wounding and ethylene could induce ACC oxidase expression of these fruits. Similarly, ACC oxidase mRNA was undetectable in the alabastrum and petal just after anthesis and rapidly accumulated during senescence, and was induced by ethylene. Petal was more sensitive to ethylene than fruit. An increase in ACC oxidase mRNA level of leaf was found after 0.5 to 8 h of wounding, but ACC oxidase mRNA accumulated more rapidly after wounding in leaf than in fruit. Ethylene seemed to have little effect on ACC oxidase expression of leaf.
Abstract (Browse 1682)  |  Full Text PDF       
Effects of Nutritional and Environmental Factors on Cell Growth and Ajmalicine Production of Full Habituated Catharanthus roseus Cells
Author: ZHENG Zhen-Gui, MIAO Hong, YANG Wen-Jie, LIU Di and HU Zhi-Bi
Journal of Integrative Plant Biology 1999 41(2)
      
    This paper deals with nutritional and environmental factors on cell growth and alkaloid accumulation and release of full habituated Catharanthus roseus (L.) G. Don cell line C20hi in suspension cultures. The effects of different initial sucrose concentration, amount of inocula, initial pH values, illuminating time, wave length of light on cell growth and ajmalicine production and release of the cell suspensions were compared. C20hi is a cell line relatively stable to environmental changes. High concentration of initial sucrose increased the biomass accumulation and alkaloid production. The suitable inoculum of C20hi was 60 g FW/L. Increasing the initial pH value in the range of 4 7 had no obvious effect to alkaloid production. Light had a detrimental effect on alkaloid production. The cells under red light could accumulate more alkaloids than that under blue light. The shaker speed of 120 r/min was found to be most suitable for C20hi suspensions.
Abstract (Browse 1781)  |  Full Text PDF       
Production of Artemisinin by Artemisia annua Hairy Root Culture in a Internal Loop Airlift Bioreactor
Author: LIU Chun-Zhao, WANG Yu-Chun, OUYANG Fan, YE He-Chun, and LI Guo-Feng
Journal of Integrative Plant Biology 1999 41(2)
      
    A self-made internal loop airlift bioreactor was used for production of artemisinin by Artemisia annua L. hairy root multi-plate culture. The hairy root cultures grew evenly either between the two meshes or attaching to the stainless steel meshes in the bioreactor. Under the optimal conditions of 12 h/d light cycle and 25 , the dry weight and artemisinin yield reached 22.57 g/L and 374.4 mg/L respectively after 20 days. Meantime, the kinetics of sugar, phosphate, nitrate and ammonium uptake during the course of culture were studied.
Abstract (Browse 1877)  |  Full Text PDF       
Major Subunits and Accumulation Pattern of Lotus Storage Proteins
Author: TANG Pei-Hua, JIANG Hua,LI Qun-Ying, JIANG Zai-Jie and ZHOU Gu
Journal of Integrative Plant Biology 1999 41(2)
      
    The content of total proteins (TP) in the mature cotyledon of red lotus (Nelumbo nucifera Gaertn) reached 24.35 g/100 g dry sample; the accumulation pattern of its storage proteins (SP) was similar to that of Leguminosae seeds, i.e. with increasing maturity, the content of SP reached abruptly to more than 86% of the TP content. Result from optical densitometry of protein SDS-PAGE in different developmental stages of the lotus cotyledon indicated that the lotus cotyledon SP included 12 major subunits (SP 1~12). In respect of MW and accumulation time, they might be divided into 3 groups. Group A had 2 subunits with the highest MW (98 kD and 93 kD) and the latest accumulation time that had the highest SP content. Group B had 3 subunits with moderate MW of 55 ~ 50 kD, their earliest accumulation time, and least SP content. And group C included 7 subunits with the lowest MW of 27~ 14 kD, moderately early accumulation time, and high SP comparatively content. By comparing the results of SDS-PAGE analysis among different varieties and organs of lotus, there was a common metabolic protein subunit with multiply connected peak. Its MW was 68 kD, which might be a common subunit of the lotus species.
Abstract (Browse 1728)  |  Full Text PDF       
Relationship Between Acetylcholine and Stomatal Movement in Vicia faba
Author: WANG Heng-Bin, WANG Xue-Chen and LOU Cheng-Hou
Journal of Integrative Plant Biology 1999 41(2)
      
    In Vicia faba L., root excision could cause a gradual decrease of the transpiration rate without affecting the shoot water potential, provided water could be supplied by other means. The lowed transpiration rate could be restored by acetylcholine. To evaluate the role of acetylcholine in this process, endogenous acetylcholine was identified by field desorption spectroscopy coupled with gas chromatography. It is shown that the acetylcholine-like substance isolated from Vicia faba seedlings exhibited a spectroscopic spectrum similar to that of the authentic acetylcholine and an extract of rat brain. These results demonstrated that acetylcholine is an endogenous substance of Vicia faba seedlings. In addition, a method of pyrolysis gas chromatography was established for determining the concentrations of acetylcholine in plants. It was found that acetylcholine contents in the abaxial epidermis exhibited a close relationship with the leaf transpiration rate and the root statues. It is speculated that acetylcholine may play an important role in the regulation of stomatal movement. This hypothesis was confirmed by the finding that acetylcholine has a stimulatory effect on stomatal aperture in the abaxial epidermis and the acetylcholine esterase inhibitor, neostigmine could increase the susceptibility of stomata to acetylcholine.
Abstract (Browse 1809)  |  Full Text PDF       
Characteristics of Calcium activated Protein Kinase in the Plasma Membrane of Corn Root Tip Cells
Author: CHEN Wu and CHEN Jia
Journal of Integrative Plant Biology 1999 41(2)
      
    Plasma membrane (PM) of high purity was prepared through a two-phase aqueous system from roots of 3 4 d old com ( Zea mays L. ) seedling, and within which calcium-activated protein kinase was identified. The kinase was mainly located in the inner side of the PM with a semi-activation concentration to free calcium ion of 50 mol/L. Exogenous CaM had no agonistic effect on the protein kinase but CaM antagonist TFP could strongly inhibit its activity with a semi-inhibition concentration of 75 mol/L. The protein kinase showed high specificity for the exogenous substrate, Histone S. These results indicated that this protein kinase could be a calcium-dependent and calmodulin-independent protein kinase (CDPK). Moreover, two proteins (33 kD and 58 kD) in PM might be the endogenous substrates of the CDPK.
Abstract (Browse 1648)  |  Full Text PDF       
Changes of Ca2+ -ATPase Activities in Cell of Rice Seed lings During the Enhancement of Chilling Resistance Induced by Cold and Salt Pretreatment
Author: ZENG Shao-Xi and LI Mei-Ru
Journal of Integrative Plant Biology 1999 41(2)
      
    The changes of Ca2+ -ATPase activities of plasmolemma, and tonoplast membrane in roots and leaf chloroplasts in rice ( Oryza sativa L. ) seedlings were investigated for exploring the mechanism of cross adaptation to different stresses in the plants during the enhancement of chilling resistance induced by cold and salt pretreatment. The results indicated that the chilling resistance of rice seedlings was enhanced markedly by cold and salt pretreatment, but this enhancement was inhibited by Ca2+-chelate ethyleneglycol-bis-(-aminoethyl ether) N, N-tetraacetic acid (EGTA) and the calmodulin inhibitor chlorpromazine (CPZ), it showed the calcium messenger system was involved in the course of chilling resistance formation. The Ca2+ -ATPase activity of root plasmolemma and tonoplast membrane as well as the Fe(CN)63- reduction in root plasmolemma in nonpretreated seedlings were declined markedly during the chilling stress. The Ca2+ -ATPase activities of plasmolemma, tonoplast membrane and chloroplasts as well as the Fe(CN)63- reduction of plasmolemma were enhanced by cold pretreatment. The activities of Ca2+ -ATPase and Fe(CN)63- reduction of plasmolemma, as compared with nonpretreated seedlings has increased by 86.80% and 93.93% respectively. The effect of salt pretreatmerit on the Ca2+ -ATPase activities of plasmolemma and chloroplast as well as Fe(CN)63- reduction of plasmolemma were similar to the effect of cold pretreatment. Although the Ca2+ -ATPase activity of tonoplast membrane was declined by salt pretreatment, the activity was none the less markedly higher than that of the nonpretreated seedlings. It showed that there was stronger ability of maintaining calcium homeostasis in the seedlings following two pretreatment. The results displayed that the enhancement of chilling resistance in rice seedlings with cold and salt pretreatment might be related to the effective activation of Ca2+ -ATPase in two pretreatment seedlings, because the activated Ca2+ -ATPase could bring back rapidly the raised cytoplasmic Ca2+ concentration from chilling stress to the state of calcium homeostasis, leading to the maintenance of normal functioning of the calcium messenger system and physiological metabolism. It seems that the adapated mechanism to chilling stress in two seedlings with cold and salt pretreatment was similar.
Abstract (Browse 1792)  |  Full Text PDF       
Studies on the Purification, Characterization and Conformati on in Solution of Metallothionein like Substance from Synechocystis 6803
Author: CHEN Zheng-Jia, LI Xiao-Fan, SHI Ding-Ji, LI Ling-Yuan and RU Bing-Gen
Journal of Integrative Plant Biology 1999 41(2)
      
    The cyanobacterium Synechocystis sp. PCC 6803 was cultivated for 5 d in sterile liquid medium BG-11 at room temperature under fluorescent light, aerated by stirring under sterile condition. ZnCl2 was then added into the medium at final concentration of 50 mol/L to induce the expression of the metallothionein-like (MT-like) compound. Five d later, the ZnCl2 concentration was increased to 100 mol/L. After 2 d, cells were collected by centrifugation, then disrupted by ultrasonic wave. After centrifugation, the supernatant was treated at 72 for 3 min to denature the unstable proteins. Again after centrifugation, the supernatant was applied to Sephacryl S-l00 molecular sieve column, then DEAE-Sepharose F. F. ion exchange column and Sephadex G-25 column for desalination. The Zn-binding fraction was frozen dried. In 5 L cultures, 7.6 g wet cyanobacterial cells were obtained. Each time the lysate of 1.52 g of them was processed, finally 1.5 mg purified MT-like compound was obtained, which was 0.1% of the total weight of wet cyanobacterial cells. Isoelectric focusing (IEF) showed that its pI was pH 4.5. Mass spectrometry and amino acid composition analysis indicated that the molecular weight of the protein was 6.986 kD. Amino acid composition analysis showed that the content of hydrophobic amino acid residues was 36%, but the Cys content was not very high (only 5% ). Ultraviolet absorption spectra showed that Zn-MT-like binding complex also had a high absorbance at 220 nm. CD spectroscopy proved that the secondary structure of this protein was a random coil, and that there were no -helix and -sheet in the structure. FT-IR spectroscopy of cyanobacterial MT-like compound was similar to that of the typical MT of mammal.
Abstract (Browse 1751)  |  Full Text PDF       
Influence of Osmotic Stress on the Lipid Physical States of Plasma Membranes from Wheat Roots
Author: QIU Quan-Sheng
Journal of Integrative Plant Biology 1999 41(2)
      
    The plasma membrane vesicles were purified from wheat ( Triticum sativum L. ) roots by the two phase partitioning method. The results showed that with the increase in sucrose concentrations, light scattering was decreased, diphenyl hexatriene (DPH) polarization and merocyanine 540 (MC540) fluorescence intensity increased, indicating that under osmotic stress the vesicles were getting smaller, the membrane fluidity and surface charge density were decreased. Further experiments showed that the long lifetime and average lifetime of DPH fluorescence decreased under stress, suggesting that plasma membrane hydrophobicity decreased. The long lifetime fluorescence of intrinsic tryptophan was also decreased, indicating that the polarity of the microenvironment surrounding the tryptophan was increased, i.e. protein conformation changed; It was also found that the H + -ATPase activity decreased with the increase in sucrose concentrations, suggesting that the membrane protein function was also affected by the physical state under osmotic stress.
Abstract (Browse 1727)  |  Full Text PDF       
Construction of Vector with IMT1 and Its Gene Expression in Transgenic Tobacco Leaf Cells Associated with Salt Tolerance
Author: DONG Yun-Zhou
Journal of Integrative Plant Biology 1999 41(2)
      
    The plant expression vector with Imtl (inositol O-methyltransferase) gene, pDH5, was constructed. The Imtl gene was introduced to tobacco (Nicotiana tabacum cv. SR1) via Agrobacterium-mediated transformation. Thirty kanamycin-resistant shoots in MSS (MSO + 1 mg/L 6-BA + 30 g/L sucrose) selective medium was transferred to MSr (MSO + 3 g/L sucrose + 7 g/L glucose) medium supplemented with 1.2%~1.5% NaC1 for rooting. Eight plantlets rooted among the thirty shoots. PCR and Southern blot assay indicated that the Irntl gene was integrated into tobacco genome in six plantlets. HPLC analysis showed that the product of Imtl gene, D-ononitol accumulated in tobacco fresh leaf cells in a scope of 100 - 654 nmol/g FW. Western blot demonstrated the expression of Imtl gene in tobacco cells.
Abstract (Browse 1741)  |  Full Text PDF       
Transformation of Cucumis melo cv. Hetau with Tomato Antisense ACC Synthase Gene
Author: LI Tian-Ran, ZHANG Zhi-Zhong, ZHANG He-Ling, MA Qing-Hu and SONG Yan-Ru
Journal of Integrative Plant Biology 1999 41(2)
      
    An efficient in vitro plant regeneration system of Cucumis melo L. cv. Hetau was established. Regenerated plantlets were obtained from cotyledons after preculture, shoot inducing culture and root inducing culture. A high regeneration rate was achieved up to 58%. Cucumis melo was transformed with the antisense tomato ACC synthase gene in binary vector pMQ6 via Agrobacterium tumefaciens mediated gene transfer. Kanamycin resistant plantlets were obtained on MS medium with 6 mg/L zeatin, 50 mg/L kanamycin and 650 mg/L cefotaximine. PCR and molecular hybridization analysis showed that tomato ACC synthase antisense cDNA was integreted into the genome of C. melo.
Abstract (Browse 1794)  |  Full Text PDF       
Selection of Cold Tolerant Somaclonal Variant from Citrus sinensis cv. Jincheng and Genetic Stability Evaluation of Its Cold Tolerance
Author: LIN Ding-Bo, YAN Qiu-Sheng and SHEN De-Xu
Journal of Integrative Plant Biology 1999 41(2)
      
    Somaclonal tolerant cell line and its regenerants were obtained from suspension culture cells of nucellar calli in Citrus sinensis (L.) Osbeck cv. Jincheng via gamma ray mutagenesis and in vitro selection with concentrated hydroxyproline, which were cold tolerant at 1.4 and 2.4 more than the suspension cells of wild types respectively. The capability of enhanced cold tolerance in the variant plantlet L3-1 was genetically stable based on a three-year evaluation. There might be slight differences between their total DNA from leaves of L3-1 and the wild type according to the polymorphism between their total DNA RAPD patterns. Except proline accumulation either at the suspension cell or at the plantlet levels, antioxygenases SOD and CAT activities were stimulated much higher and MDA contents much lower than the wild type after cold acclimation at the suspension cell levels, which indicated that physiological mechanism on the enhanced cold tolerance of the variant was very complex. Not only proline metabolism, but antioxygenases and some others were also involved in its enhancement process on cold hardiness.
Abstract (Browse 1797)  |  Full Text PDF       
An Alternative Mode of Elimination of Resin from Epithelial Cells of Resin Ducts in Pinus sylvestris
Author: WU Hong and Martin MLLER
Journal of Integrative Plant Biology 1999 41(2)
      
    The fine structure of resin secreting cells of the cortical resin ducts in stem of Pinus sylvestris Carr. was studied with the help of high pressure freezing and freeze-substitution techniques. An unprecedented mode of resin elimination was observed. It seems that the hydrolase-contained Golgi vesicles take part in the dissolution of plasmalemma, and a passage is formed, through which resin material may quickly pass outside of the protoplast. Then, the ruptured plasmalemma was repaired by some vesicles, possibly derived from Golgi bodies.
Abstract (Browse 1713)  |  Full Text PDF       
The Mechanism of Pollination in Platycladus orientalis and Thuja occidentalis (Cupressaceae)
Author: XING Shu-Ping, ZHANG Quan,HU Yu-Xi,CHEN Zu-Keng and LIN Jin-Xing
Journal of Integrative Plant Biology 1999 41(2)
      
    The pollination mechanisms of Platycladus orientalis (L.) Franco and Thuja occidentalis L. seem to be of the same type, as based on the morphological study of the change in pollination drop, during the process of pollination. Entering the pollination drop, the pollen may alter the surface of the drop or reduce the secretion of the ovule with concomitant increase of evaporation. It has been further noticed that the dynamic change of the drop withdrawal rate was closely associated with the different kinds of pollen received. It seems that the withdrawal of the pollination drop may be induced by pollen from plants consanguineous to P. orientalis, almost as effective as from pollen of P. orientalis itself and comparatively more effective than the foreign pollen received from distant plant species. The drop withdrawal could be mainly induced by the pollen that causes the reduction of ovule secretion.
Abstract (Browse 1949)  |  Full Text PDF       
Ultracytochemical Localization of Calcium in the Gynoecium and Embryo Sac of Rice
Author: YU Fan-Li, ZHAO Jie, LIANG Shi-Ping, YANG Hong-Yuan
Journal of Integrative Plant Biology 1999 41(2)
      
    Potassium pyroantimonate precipitation method was used for ultracytochemical localization of calcium in rice ( Oryza sativa L. ) stigma, style, ovary and embryo sac before and after fertilization. To identify the nature of the pyroantimonate deposits, the energy-dispersive X-ray microanalysis (EDXA) was employed and the deposits observed were proved as calcium pyroantimonate. Transmission electron microscopic observations revealed that abundant deposits were present at the surface of stigma papillae and parenchymatous cells of style. One day before anthesis, when the embryo sac was immature and contained a few deposits, calcium distribution showed no difference between two synergids. By the time just prior to anthesis, one of the synergids that had degenerated accumulated more calcium than before, and than the other synergid. Six hours after anthesis at time when double fertilization had finished, the calcium deposits in the degenerated synergid increased. Before fertilization, the deposits in the egg cell were mainly localized in the vacuoles, whereas few deposits could be observed in the nucleus and cytoplasm. After fertilization, the amount of calcium increased dramatically in the zygote, especially in its nucleus. The results are discussed in relation to the role of calcium in mediating synergid degeneration and egg activation.
Abstract (Browse 1756)  |  Full Text PDF       
Systemic Acquired Disease Resistance and Signal Transduction in Plant
Author: YU Di-Qiu, CEN Chuan,LI Bao-Jian and Fu Jia-Rui
Journal of Integrative Plant Biology 1999 41(2)
      
    In recent years there has been a large body of evidence to suggest that plants have a variety of active mechanisms for defending themselves against microbial pathogenic infections. The development of systemic acquired resistance (SAR) and its signal transduction pathway are associated with increased expression of a large number of defense or defense-related genes. Salicylic acid (SA) is an important signaling molecule in the induction of disease resistance and the establishment of SAR in plants. There have been two kinds of possible mechanisms in the establishment of SAR and its signal transduction pathway among plants.
Abstract (Browse 1882)  |  Full Text PDF       
Morphological Studies on Megaspore Formation in Ginkgo biloba
Author: JI Cheng-Jun, YANG Xiong and LI Zheng-Li (Lee C L)
Journal of Integrative Plant Biology 1999 41(2)
      
    Polarity of megasporocyte in Ginkgo biloba took place before the initiation of meiosis. At first the nucleus of megasporocyte moved from the central portion to the micropyle end and later a vacuole appeared at the chalazal end and existed throughout the process of meiosis. The meiotic divisions of the megasporocyte were unequal and nonsynchoronous. The megaspore tetrads were mostly linearly arranged but sometimes T-shaped. T-shaped tetrads were apparently a result from an inclined division of a dyad cell which faced toward the micropyle end. A sequencial difference in the cell size of the tetrad, i. e. the largest at the chalazal end to the smallest at the micropyle end could be seen at its early developmental stage.
Abstract (Browse 1641)  |  Full Text PDF       
Petroleum Sporo-pollen Assemblages and Petroleum Source Rocks of North Tarim Upheaval in Xinjiang
Author: JIANG De-Xin and YANG Hui-Qiu
Journal of Integrative Plant Biology 1999 41(2)
      
    One hundred and thirty-five species of fossil spores and pollen referred to 66 genera which were extracted from the crude oil samples collected from the North Tarim petroliferous region of the Tarim Basin were identified. Based on the investigations of the characteristics of the petroleum sporo-pollen assemblages, the geological ages and formations of the petroleum source rocks of the petroliferous region were determined. Some aspects concerning the avenues, directions, mutes, periodic sequences of oil and gas migration were also discussed. The results of this study confirm that the following Formations, viz. the Middle Triassic Karamay Formation, the Upper Triassic Huangshanjie and Taliqike Formations, the Lower Jurassic Ahe and Yangxia Formations, and the Middle Jurassic Kezilenuer and Qiakemake Formations should be the important petroleum source rock series of the North Tarim petroliferous region.
Abstract (Browse 1749)  |  Full Text PDF       
Chemical Constituents from the Bark of Cercidiphyllum japonicum
Author: WANG Jing-Rong, DUAN Jin-Ao and ZHOU Rong-Han
Journal of Integrative Plant Biology 1999 41(2)
      
    Eight compounds were isolated from the bark of Cercidiphyllum japonicum Sieb. et Zucc. Their structures were identified with spectral and chemical methods as 5, 7-dihydroxy-3, 8, 4-trimethoxyflavone (), 3,5,7-trihydroxy-8,4-dimethoxyflavone (), 5,7,4-trihydroxy -3,8-dimethoxyflavone (), 3,5, 7,4-tetrahydroxy-8-methoxyflavone (), 3, 5, 7,4-tetrahydroxyflavone (), 5,7-dihydroxy-8,4-dimethoxy-3-O-glucoside (), 5,7,4-trihydroxy-8-methoxyflavone-3-O-glucoside (). One phenol acid compound was identified as ethyl gallate ( ). Among them, compound is a new compound that has never been reported. Except compound , all the other compounds were isolated from this genus for the first time.
Abstract (Browse 1879)  |  Full Text PDF       
Structural Identification of Kudinchagenin I
Author: WEN Yong-Xin,LIANG Xiao-Yan, CHENG Gui-Ren, WU Nan, KANG Wen-Jun,ZHENG Qi-Tai and L Yang
Journal of Integrative Plant Biology 1999 41(2)
      
    A novel triterpenoid, kudinchagenin was isolated from the leaves of Ilex kudincha C. J. Tseng and its structure was determined to be 3-hydroxy- 11 (12), 13 ( 18 ), 19 ( 29 ) - triene-28,20-lactonic-ursane by a combination of spectroscopic methods and single crystal X-ray analysis.
Abstract (Browse 1801)  |  Full Text PDF       
Distribution Characteristics of Patch Sizes in the Vegetation Landscape in Beijing
Author: LIU Can-Ran and CHEN Ling-Zhi
Journal of Integrative Plant Biology 1999 41(2)
      
    The vegetation map on the scale of one to two hundred thousandth in Beijing was digitized and analyzed with GIS software ARC/INFO. In this map, there are 72 lower level patch types in total, and they belong to 6 higher level patch types, viz. forest, shrubland, grassland, orchard, cropland and waters, which include 20, 28, 4, 7, 11 and 2 lower level patch types respectively. Several basic descriptive statistics and five types of probability distributions, which include Gamma, negative exponential, lognormal, Weibull, and normal distributions, were chosen to characterize the patch size distributions for all the patch types in Beijing area. The results show that the patch size distributions for most of the 72 lower level types and all the 6 higher level types are right-skewed. Therefore, normal distribution cannot be used to characterize the patch size distributions in this area; and each of the other four probability distributions can only depict part of the types. The patch types that can be characterized with lognormal distribution are relatively more, and those with negative exponential distribution are fewer.
Abstract (Browse 1785)  |  Full Text PDF       
Effects of Severing Rhizome on Clonal Growth in Rhizomatous Grass Species Psammochloa villosa and Leymus secalinus
Author: DONG Ming
Journal of Integrative Plant Biology 1999 41(2)
      
    A field experiment was conducted in Inner Mongolian dune to investigate the contribution of clonal integration to genet expansion and ramet establishment in clonal plants in semi-arid inland dune. In the experiment, the developing parts (plant observing unit) of two rhizomatous grass species Psammochloa villosa (Trin.) Bor and Leymus secalinus (Georgi.) Tzvel. were subjected to the treatment of severing rhizomes. The 7 characters relevant to the elonal growth of the plant observing units were investigated such as total length of shoots, number of shoots, number of rhizomes, length of main rhizome, total length of rhizomes, number of main rhizome nodes and total number of rhizome nodes. The results showed that the increments in those plant characters were reduced by the treatment in P. villosa, while no effect of the treatment was observed in L. secalinus. The results suggest an interspecific difference in clonal integration and in its contribution to clonal growth. In P. villosa, clonal integration and clonal growth offer great contributions to the survival of the plants in the sandy grassland characterized where water shortage, strong transevaporation, infertility, habitat patchiness and frequent disturbance were most characteristic.
Abstract (Browse 1936)  |  Full Text PDF       
Seasonal Changes in Photosynthetic Characteristics of Ammopiptanthus mongolicus
Author: LI Wen-Rui, FENG Jin-Chao, JIANG Tian-Ran, ZHANG Li-Xin and LIU Xin-Min
Journal of Integrative Plant Biology 1999 41(2)
      
    Seasonal changes in the photosynthetic characteristics of Ammopiptanthus mongolicus (Maxim.) Chen f. were studied. When the net photosynthetic rate decreased with the elevation of air temperature, the stomata conductance and stomatal limitation value tended to decline simultaneously, while the intercellular CO2 concentration was increased. According to the two criteria discriminating the stomatal limitation of photosynthesis suggested by Farquhar and Sharkey, the seasonal changes in these parameters indicated that the decrease in Pn, may not be due to stomatal factor. These studies proved that the relative contents of the large subunit of Rubisco and the photochemical activities correlated with the seasonal changes in the net photosynthetic rate, which may show that these two factors contribute primarily to the seasonal changes in CO2 assimilation.
Abstract (Browse 1915)  |  Full Text PDF       
 

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