白茅生长及抗氧化酶系统对铜胁迫的生理响应

通过盆栽实验研究了重金属Cu递进胁迫对白茅幼苗生理生态及抗氧化酶系统的影响。结果表明,随着Cu浓度的增加,平均根长、平均株高、鲜重、干重以及叶片色素含量等指标先增后降,分别在Cu浓度500 mg/kg处达到峰值。最长根长和叶片可溶性蛋白含量则在1000 mg/kg处达到峰值。说明低浓度Cu（〈500 mg/kg）对白茅生长有促进作用,而高浓度Cu（〉1000 mg/kg）则对植株生长产生抑制作用。Cu胁迫还导致叶片细胞膜脂过氧化水平增高,表现为叶片MDA含量随Cu浓度增加而持续上升,其最大值达到对照的5.3倍。抗氧化酶系统中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和多酚氧化酶（PPO）活性也随Cu浓度增加表现出先升后降的趋势,并均在Cu浓度为1000 mg/kg时达到峰值,但过氧化物酶（POD）活性持续上升,故系统受到高浓度Cu胁迫而失衡,不能有效清除植物体的自由基和过氧化物,使植物产生受害症状。     

白茅对紫茎泽兰的竞争效应

外来生物的入侵可导致环境退化、生物多样性降低和食物及水资源短缺,利用本地植物或优良牧草进行替代控制是治理入侵植物的有效途径之一。采用本地禾本科植物白茅与紫茎泽兰等比例混合种植,研究了其对紫茎泽兰的竞争效应。结果表明:白茅与紫茎泽兰之间呈现很强的竞争作用,可用作紫茎泽兰的替代控制植物;白茅地上部分相对竞争力比紫茎泽兰强,其幼苗萌发早于紫茎泽兰,株高和单株平均叶面积均显著高于紫茎泽兰;二者混合种植可显著抑制紫茎泽兰的植株生长和分蘖,混合种植区紫茎泽兰的株高、单株平均叶面积和叶绿素含量分别只有其单种的49%、72%和77%;而混合种植对白茅植株生长的影响不显著,并可促进其分蘖,混合种植区的白茅分蘖数达单种区的132%。白茅的相对产量显著高于紫茎泽兰的对应指标,竞争效应参数相对产量总和1.0;随着混合种植时间的延长,两者的竞争关系将愈加显著。     

Cytological evidence for chromosome elimination in wheat x Imperata cylindrica hybrids

Haploid induction of wheat by crossing with Imperata cylindrica pollen is an efficient method for doubled haploid breeding. We investigated the process of wheat haploid formation after crossing with I. cylindrica. Our cytological observations of zygotes showed the successful fertilization of parental gametes. Wheat haploids were formed by complete elimination of I. cylindrica chromosomes. Missegregation of I. cylindrica chromosomes was observed in the first cell division of zygote. At metaphase I. cylindrica chromosomes did not congress onto the equatorial plate. The sister chromosomes did not move toward the poles during anaphase, though their cohesion was released normally. I. cylindrica chromosomes were still in the cytoplasm at telophase and eliminated from daughter nuclei. After two-celled stage, we could find no I. cylindrica chromosome in the nuclei but micronuclei containing I. cylindrica chromatin in the cytoplasm. These observations indicate that I. cylindrica chromosomes are completely eliminated from nuclei in the first cell division probably due to lack of functional kinetochores.     

Physiological studies in salinity tolerance ofSesbania aculeata POIR

A pot culture experiment was performed to evaluate salt tolerance potential ofSesbania aculeata Poir. The plant can tolerate salinity levels up to electrical conductivity (ECe), 10 mS cm^?1 and at 15 mS cm^?1 thero is about 40% reduction in dry matter production. The analysis of inorganic constituents in different plant parts revealed that the plant has the capacity to regulate sodium uptake under saline conditions and chloride uptake always exceeded that of sodium. The potassium: sodium ratio is also maintained at a fairly constant level in leaflets while it is reduced in leaf rachis, stem and roots. Salt stress caused accumulation of calcium and magnesium in all plant parts. A considerable decline in phosphorus uptake was observed due to salinity. Iron was found to be accumulated more in salt stressed roots only. Nitrogen accumulated in both roots and leaves while considerable proline accumulation was observed in leaves of salt stressed plants. The amount of soluble sugars was increased in roots and leaves due to salt stress, while starch content of roots decreased. Those changes induced by salinity are discussed in relation to salt tolerance capacity of the plant.     

Physiological and proteomic analysis of salinity tolerance in Puccinellia tenuiflora

Soil salinity poses a serious threat to agriculture productivity throughout the world. Studying mechanisms of salinity tolerance in halophytic plants will provide valuable information for engineering plants for enhanced salt tolerance. Monocotyledonous Puccinellia tenuiflora is a halophytic species that widely distributed in the saline-alkali soil of the Songnen plain in northeastern China. Here we investigate the molecular mechanisms underlying moderate salt tolerance of P. tenuiflora using a combined physiological and proteomic approach. The changes in biomass, inorganic ion content, osmolytes, photosynthesis, defense-related enzyme activities, and metabolites in the course of salt treatment were analyzed in the leaves. Comparative proteomic analysis revealed 107 identities (representing 93 unique proteins) differentially expressed in P. tenuiflora leaves under saline conditions. These proteins were mainly involved in photosynthesis, stress and defense, carbohydrate and energy metabolism, protein metabolism, signaling, membrane, and transport. Our results showed that reduction of photosynthesis under salt treatment was attributed to the down-regulation of the light-harvesting complex (LHC) and Calvin cycle enzymes. Selective uptake of inorganic ions, high K(+)/Na(+) ratio, Ca(2+) concentration changes, and an accumulation of osmolytes contributed to ion balance and osmotic adjustment in leaf cells. Importantly, P. tenuiflora plants developed diverse reactive oxygen species (ROS) scavenging mechanisms in their leaves to cope with moderate salinity, including enhancement of the photorespiration pathway and thermal dissipation, synthesis of the low-molecular-weight antioxidant α-tocopherol, and an accumulation of compatible solutes. This study provides important information toward improving salt tolerance of cereals.     

Anatomical adaptations to salinity in cogon grass [Imperata cylindrica (L.) Raeuschel] from the Salt Range, Pakistan

To examine anatomical adaptations in a potential forage grass, Imperata cylindrica (L.) Raeuschel, a population was collected from the natural salt-affected soils of the Salt Range, Pakistan. Using a hydroponic system, the degree of salt tolerance in terms of structural modifications in the Salt Range ecotype was compared with that in an ecotype collected from a normal non-saline habitat of the Faisalabad region. The Salt Range ecotype was superior to the Faisalabad ecotype in biomass production under saline conditions. High salt tolerance of the Salt Range ecotype was associated with increased succulence in root and leaf (mainly midrib), formation of aerenchyma in leaf sheath, increased vascular bundle area, metaxylem area and phloem area, highly developed bulliform cells on leaves and increased sclerification in root and leaf. Furthermore, both stomatal density and stomatal area were considerably reduced under high salinities in the Salt Range ecotype.     

白茅的组织培养及植株再生

1　植物名称　白茅 (Ｉｍｐｅｒａｔａｃｙｌｉｎｄｒｉｃａｖａｒ.ｍａ ｊｏｒ) ,又称茅草、茅针。2　材料类别　茎生长点和根状茎的节间组织。3　培养条件　从野外采回丛生茎和根状茎后 ,除净叶片及须根等 ,用清水反复冲刷干净 ,剪成茎具生长点、根状茎具节间的茎段 ,分别放到超净工作台上 2 5 0ｍｌ磨口广口瓶中 ,用 70 %乙醇灭菌 30ｓ后 ,在 0 .0 4 %ＨｇＣｌ2 溶液中 ,手摇振荡灭菌茎 1 0ｍｉｎ ,根状茎 2 0ｍｉｎ ,倒净灭菌液 ,再用无菌水振荡冲洗 5次 ,在茎上端切取 0 .2～ 0 .4ｃｍ茎尖 ,根状茎的节间切成约 0 .2ｃｍ茎段。培养基 :…     

Composition, speciation and distribution of iron minerals in Imperata cylindrica.

A comparative study of the roots, rhizomes and leaves of an iron hyperaccumulator plant, Imperata cylindrica, isolated from the banks of an extreme acidic environment, using complementary techniques: Mösbauer spectroscopy (MS), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled to energy-dispersive X-ray microanalysis (EDAX) and transmission electron microscopy (TEM), has shown that two main biominerals, jarosite and ferrihydrate-ferritin, accumulate in the different tissues. Jarosite accumulates mainly in roots and rhizomes, while ferritin has been detected in all the structures. A model of iron management in I. cylindrica is presented.     

Effects of glyphosate on interspecific competition between Solidago canadensis and Imperata cylindrica

Aims The extensive use of herbicide to control invasive plants would change the relationship between alien and neighboring plants. In order to provide data for rational use of herbicide and a theoretical reference for further studies on the ecological effects of glyphosate, we explored the variation of the relationship between an invasive plant Solidago canadensis and a native plant Imperata cylindrica when they were sprayed glyphosate.
Methods A replacement series experiment was conducted from June to August 2016 in Wetland Ecosystem Research Station of Hangzhou Bay, State Forestry Administration, to examine the effects of glyphosate at seven concentration levels (0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8 mL·L^-1) on the growth and interspecific competition of S. canadensis and I. cylindrica.
Important findings (1) Glyphosate treatment significantly inhibited the growth of S. canadensis and I. cylindrica (p < 0.05). During the test, cumulative growth of height and leaf number of S. canadensis were apparently reduced with the increase of glyphosate concentration, but the leaf number of S. canadensis treated with 0.3- 1.5 mL·L^-1 glyphosate was re-growing with time, while the one treated with 1.8 mL·L^-1 was mostly dead. The withering rate of tiller and green leaf of I. cylindrica also significantly increased with the increase of glyphosate concentration, and the growth indices of this plant treated with 0.3-0.6 mL·L^-1 were also re-growing with time. (2) Glyphosate treatment significantly affected interspecific competition (p < 0.05), which diminished as the glyphosate concentration increased. (3) Interspecific competition has significant influence on the biomass allocation of S. canadensis (p < 0.05). When facing competition, S. canadensis would allocate more organic matter to root and thus increase the ratio of root to shoot. Competition only inhibited the tiller number and total biomass of I. cylindrica, but insignificantly affected its ratio of root to shoot. (4) The interaction between glyphosate treatment and S. canadensis-I. cylindrica interspecific relationship also significantly influenced the biomass of S. canadensis and I. cylindrica (p < 0.05), but insignificantly affected the root/shoot ratio of two plants. Different plants have different tolerance to glyphosate stress. Compared with native plant I. cylindrica, S. canadensis has stronger tolerance to glyphosate. Low-concentration glyphosate could decrease the competitive intensity between S. canadensis and I. cylindrica, which may disturb the structure and dynamics of plant communities.     

Role of species identity in plant invasions: experimental test using Imperata cylindrica

The role of species richness, functional diversity and species identity of native Florida sandhill understory species were tested with Imperata cylindrica, an exotic rhizomatous grass, in mesocosms. I. cylindrica was introduced 1 year after the following treatments were established: a control with no native species, five monocultures, a grass mix treatment, a forb mix treatment, and a 3-species treatment and a 5-species treatment. Monthly cover, final biomass, root length, root length density (RLD) and specific root length (SRL) of all species were determined for one full growing season. There was a significant negative linear relationship between the cover of native species and I. cylindrica (r ² = 0.59, P = 0.01) and a negative logarithmic relationship between the biomass of native species and I. cylindrica (r ² = 0.70, P = 0.003). There was no diversity–invasibility relationship. Grasses proved to be the most resistant functional group providing resistance alone and in mixed functional communities. Repeated measures analysis demonstrated that treatments including Andropogon virginicus were the most resistant to invasion over time (P < 0.001). Significantly greater root length (P = 0.002), RLD (P = 0.011) and SRL (P < 0.001) than all of the native species and I. cylindrica in monocultures and in mixed communities made A. virginicus successful. The root morphology characteristics allowed it to be a great competitor belowground where I. cylindrica was most aggressive. The results suggest that species identity could be more important than species or functional richness in determining community resistance to invasion.     

A PCR-based Genotyping Method to Distinguish Between Wild-type and Ornamental Varieties of Imperata cylindrica

Wild-type I. cylindrica (cogongrass) is one of the top ten worst invasive plants in the world, negatively impacting agricultural and natural resources in 73 different countries throughout Africa, Asia, Europe, New Zealand, Oceania and the Americas^1-2. Cogongrass forms rapidly-spreading, monodominant stands that displace a large variety of native plant species and in turn threaten the native animals that depend on the displaced native plant species for forage and shelter. To add to the problem, an ornamental variety [I. cylindrica var. koenigii (Retzius)] is widely marketed under the names of Imperata cylindrica ''Rubra'', Red Baron, and Japanese blood grass (JBG). This variety is putatively sterile and noninvasive and is considered a desirable ornamental for its red-colored leaves. However, under the correct conditions, JBG can produce viable seed (Carol Holko, 2009 personal communication) and can revert to a green invasive form that is often indistinguishable from cogongrass as it takes on the distinguishing characteristics of the wild-type invasive variety⁴ (Figure 1). This makes identification using morphology a difficult task even for well-trained plant taxonomists. Reversion of JBG to an aggressive green phenotype is also not a rare occurrence. Using sequence comparisons of coding and variable regions in both nuclear and chloroplast DNA, we have confirmed that JBG has reverted to the green invasive within the states of Maryland, South Carolina, and Missouri. JBG has been sold and planted in just about every state in the continental U.S. where there is not an active cogongrass infestation. The extent of the revert problem in not well understood because reverted plants are undocumented and often destroyed.Application of this molecular protocol provides a method to identify JBG reverts and can help keep these varieties from co-occurring and possibly hybridizing. Cogongrass is an obligate outcrosser and, when crossed with a different genotype, can produce viable wind-dispersed seeds that spread cogongrass over wide distances^5-7. JBG has a slightly different genotype than cogongrass and may be able to form viable hybrids with cogongrass. To add to the problem, JBG is more cold and shade tolerant than cogongrass^8-10, and gene flow between these two varieties is likely to generate hybrids that are more aggressive, shade tolerant, and cold hardy than wild-type cogongrass. While wild-type cogongrass currently infests over 490 million hectares worldwide, in the Southeast U.S. it infests over 500,000 hectares and is capable of occupying most of the U.S. as it rapidly spreads northward due to its broad niche and geographic potential^3,7,11. The potential of a genetic crossing is a serious concern for the USDA-APHIS Federal Noxious Week Program. Currently, the USDA-APHIS prohibits JBG in states where there are major cogongrass infestations (e.g., Florida, Alabama, Mississippi). However, preventing the two varieties from combining can prove more difficult as cogongrass and JBG expand their distributions. Furthermore, the distribution of the JBG revert is currently unknown and without the ability to identify these varieties through morphology, some cogongrass infestations may be the result of JBG reverts. Unfortunately, current molecular methods of identification typically rely on AFLP (Amplified Fragment Length Polymorphisms) and DNA sequencing, both of which are time consuming and costly. Here, we present the first cost-effective and reliable PCR-based molecular genotyping method to accurately distinguish between cogongrass and JBG revert.     

Restoration of natural vegetation in degraded Imperata cylindrica grassland: understorey development in forest plantations

Abstract. Reclamation of former, degraded forest lands occupied by Imperata cylindrica is one of the crucial environmental and forestry issues in the humid tropics, notably Southeast Asia. We suggest that it is possible to gradually restore the original natural forest cover with the help of a sacrifice fallow crop of fast-growing exotic tree species. Recently, a set of suitable fast-growing plantation tree species has been identified and stand establishment methods developed for this purpose. We assessed the regeneration of natural vegetation in stands of different plantation tree species and evaluated the ecological impact of species composition in the plantation understorey. PCA ordination, regression analysis and analysis of covariance were applied at different stages of the study. We found a marked vegetational resemblance between stands dominated by Acacia mangium: they had the highest number of indigenous trees in their understorey, whereas stands of other plantation trees supported more diverse grass and herb vegetation. A high proportion of evergreen woody vegetation reduces the risk of fire and grass competition and enhances secondary succession towards natural forest.     

Effects of weed abundance and frequency of hand weeding on the establishment of transplanted Imperata cylindrica

Imperata cylindrica is an important component of grasslands in several Asian countries. Its vigorous rhizome elongation enables the plant to quickly cover bare ground, making it a candidate for revegetation projects. In these projects, initial and subsequent management practices often differ. Initial management strategies are important for encouraging rapid cover by the target species. We tested the effects of initial hand weeding on I. cylindrica cover and weed growth over 2 years. Two types of soil (A and B) were scattered on a recently constructed river embankment at a depth of 10 cm. Both soils A and B are nutrient-poor and high (> 7.0) pH. Plots were hand-weeded once or twice a year (W₁ and W₂ treatments, respectively), or mowed but not weeded (M treatment) with four replications. Plug plants of I. cylindrica were introduced. I. cylindrica became dominant in soil A with the W₂ treatment, with 50% cover in year 2. Conversely, I. cylindrica failed to establish in soil B regardless of treatment, due to dominance of the weed Sorghum halepense. Soil B included creeping rhizomes of S. halepense, and vigorous growth from rhizomes is likely a major reason for its predominance. S. halepense seedlings germinated in both soils, but were successfully eradicated when weeded at less than 1 month of age. Thus, for successful revegetation, land managers should use soil that does not contain creeping rhizomes of S. halepense. If rhizomes are not present, hand weeding twice a year for 2 years is sufficient for establishment of I. cylindrica.

     

Some competition experiments with alang-alang (Imperata cylindrica (L.) Beauv.) in replacement series

Summary The interaction between alang-alang (Imperata cylindrica) and maize or sorghum was studied in competition experiments according to the replacement principle. Dry matter yield of alang-alang in these experiments appeared hardly affected by the presence of maize or sorghum, while this yield of the latter two was strongly reduced by the presence of alang-alang. The relative yield total (RYT) reached unity except in one experiment in which a value of 0.6 was obtained.The results suggest that the allelopathic activity of alang-alang will find expression in an RYT deviating from one only if alang-alang is not able to utilize all available space.Part of the research supported by the Netherlands Foundation for Advancement of Tropical Research (WOTRO) grant W86-34     

Silicon in Imperata cylindrica (L.) P. Beauv: content,distribution, and ultrastructure

Silicon concentration, distribution, and ultrastructure of silicon deposits in the Poaceae Imperata cylindrica (L.) P. Beauv. have been studied. This grass, known for its medicinal uses and also for Fe hyperaccumulation and biomineralization capacities, showed a concentration of silicon of 13,705?±?9,607 mg/kg dry weight. Silicon was found as an important constituent of cell walls of the epidermis of the whole plant. Silica deposits were found in silica bodies, endodermis, and different cells with silicon-collapsed lumen as bulliforms, cortical, and sclerenchyma cells. Transmission electron microscope observations of these deposits revealed an amorphous material of an ultrastructure similar to that previously reported in silica bodies of other Poaceae.     

Mechanisms of salinity tolerance in plants

The mechanisms of salt stress response and tolerance have eluded definition despite reasonable success in defining their physiological manifestations. In this review, we consider the integrated salt metabolism of plants, essentially as a problem in meganutrient physiology. Two critical aspects of cellular and organismal metabolism are given particular attention—those involved in the control and integration of Na⁺ acquisition and allocation in plants and those involved in readjustment of other aspects of metabolism, especially those involving carbon as a resource.     

Evaluating hybridization as a potential facilitator of successful cogongrass (Imperata cylindrica) invasion in Florida,USA

Interspecific hybridization is cited as one potential mechanism for increased invasiveness, particularly among some grass species. In the southeastern United States, the successful invasion of cogongrass (Imperata cylindrica) has sometimes been attributed to hybridization with the previously naturalized Imperata brasiliensis. This research aimed to determine whether genetic signals are consistent with these two species having experienced interspecific hybridization in Florida (USA), where it has been proposed that such an event facilitated cogongrass invasion across the region. Individuals of invasive I. cylindrica populations (n = 66) were sampled broadly from the state, and I. brasiliensis (n = 63) individuals were sampled from expertly identified and vouchered populations in Miami-Dade County. Genetic analysis utilized amplified fragment length polymorphisms in sampled individuals, and failed to detect significant genetic differentiation between the two species. Analysis of molecular variance partitioned the majority of detected variation within populations (86 %), while only 8 % was significantly partitioned between I. cylindrica and I. brasiliensis (F_ST = 0.135, P < 0.001). Both STRUCTURE analysis and principal coordinates analysis strongly indicated the presence of a single genetic group across the sampled populations. Hybrid analysis furthermore failed to support interspecific hybridization. Florida populations thus are suggested to share genetic parent material(s) and/or have experienced substantial admixture across the state. Therefore, this study suggests Imperata populations in South Florida that are currently considered to be I. brasiliensis are not genetically distinct from I. cylindrica, and regional cogongrass invasion likely was not facilitated by previously postulated interspecific hybridization.     

Leaf litter decomposition of Piper aduncum,Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea

No information is available on the decomposition and nutrient release pattern of Piper aduncum and Imperata cylindrica despite their importance in shifting cultivation systems of Papua New Guinea and other tropical regions. We conducted a litter bag study (24 weeks) on a Typic Eutropepts in the humid lowlands to assess the rate of decomposition of Piper aduncum, Imperata cylindrica and Gliricidia sepium leaves under sweet potato (Ipomoea batatas). Decomposition rates of piper leaf litter were fastest followed closely by gliricidia, and both lost 50% of the leaf biomass within 10 weeks. Imperata leaf litter decomposed much slower and half-life values exceeded the period of observation. The decomposition patterns were best explained by the lignin plus polyphenol over N ratio which was lowest for piper (4.3) and highest for imperata (24.7). Gliricidia leaf litter released 79 kg N ha^–1, whereas 18 kg N ha^–1 was immobilised in the imperata litter. The mineralization of P was similar for the three species, but piper litter released large amounts of K. The decomposition and nutrient release patterns had significant effects on the soil. The soil contained significantly more water in the previous imperata plots at 13 weeks due to the relative slow decomposition of the leaves. Soil N levels were significantly reduced in the previous imperata plots due to immobilisation of N. Levels of exchangeable K were significantly increased in the previous piper plots due to the large addition of K. It can be concluded that piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato. Gliricidia leaf litter contained much N, whereas imperata leaf litter releases relatively little nutrients and keeps the soil more moist. Gliricidia fallow is more attractive than an imperata fallow for it improves the soil fertility and produces fuelwood as additional saleable products.