ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Plant Evolution & Ecology (4): Soil

Updated on June 5, 2012

Hui Yan

Winder, R.S. and Macey, D.E. 2001. The influence of edaphic and competitve factors on productivity of marsh reed grass (Calamagrostis canadensis) in a cooperative pathosystem. Canada Journal of Botany 79: 805-814.



Weed pathogens refer to virus, bacteria, or fungus that cause disease to their hosts, e.g. weeds or crops, and thus pathogens can be used to be as herbicides. However, such a use is greatly limited by some ecological and environmental factors. For example, some weeds may have developed adaptive shapes or genetic resistance to these pathogens.

Marsh reed grass, Calamagrostis canadensis, is a weedy species that can n typically damage the seedlings of coniferous trees in boreal forests. The tiny seeds of C.canadensis are dispersedprevailed by wind in late summer, and seedlings grow fast with spreading roots. The grass forms a thatch that damages conifer seedlings and is difficult to control. If C.canadensis can be controlled by pathogens at the earliest stage, then conifers will have enough time to grow.

Previous studies show that the cooperative infections of two kinds of pathogens, such as fungi and rhizobacteria (i.e. bacteria living on roots), can result in more damage to marsh reed grass, but the amount of damage they do is influenced by other factors, such as soil fertility or competition. For instance, high Nitrogen availability may improve the growth of plants and thus compensate for the damage or disease caused by pathogens.

The study examined the influence of edaphic and competitive factors on the productivity of C.canadensis exposed to the FPCP pathogens (a fungus, F.avenaceum combined with a bacteria, P.seudomonas) under greenhouse conditions. The experiment focuses on the influence of FPCP on leaves, because the accumulation of leaves makes heavy snow difficult to thaw so that heavy snow causes straw to suppress conifer seedlings. The specific objectives of the study were to determine the interactive effects of autoallelopathy, competition, and nutrient availability on the efficacy of the FPCP for suppressing growth in marsh reed grass seedlings.

*Autoallelopathy: a substancethat plants produce by themselves, such as toxin, and the substance can hurt themselves.

C.canadensis | Source

Materials and methods

Grass seeds were collected in late summer, and sown the following spring in plastic pots with coal-like thingsto hold nutrients and plastic dishes to contain water and released nutrients.

The pathogen complex was created using F.avenaceumisolated from wheat, and Pseudomonas isolated fromthe roots of C.canadensis. A group of treatments were inoculated with the pathogen complex, and another group uninoculated are control experiments to compare results.

The study tested the responses of the two group of treatments to individual factor of autoallelopathy(i.e. straw extract), competition, and soil nutrients, and to combinations of any two of the three factors.


Autoallelopathy versus competition

The FPCP complex damaged leaves and inhibited shoot growth under all conditions. Competition had much clearer inhibition on growth of uninoculated plants than on inoculated ones, and increased the leaf damage of inoculated plants; the straw extract caused no change in inoculated plants, and increased leaf damage; a three-way interaction between inoculation, competition and straw extract caused a complicated response: 1) low concentrations of straw extract reduced the inhibition of growth by competition, but the inhibition was enhanced by higher concentrations. 2) increased concentrations of straw extract caused increased damage of plants with highest competition, but the highest increase in damage happened with intermediate concentration.

Autoallelopathy versus N, P, and K

Independently, N addition greatly enhanced the growth of seedlings without pathogen disease, and P, K did not have obvious effects on growth. In the case of inoculation, N, P and K only caused slight changesin growth. Interaction between inoculation, extract, N, P and K showed that extract negatively influenced growth; P-addition? greatly enhanced leaf damage, and P-addition combined with extract doubled leaf-damage.

Competition versus nutrients

Without pathogens, competition inhibited the growth, but nutrient fertilization increased the growth. With pathogens, the inhibition by competition was modified; plants with the lowest competition were more responsive to fertilizer than those with the highest competition, and the degree of the leaf damage decreased as the fertilizers and competition levels increased.


Firstly, in the case of low nutrients, shoot growth increased with leaf damage, which means that the growth of inoculated plants was unaffected by changes of N, P and K. And therefore, the increased leaf damage by P and K imbalances did not limit the early seedling growth.

Secondly, the interaction between straw extract and competition greatly decreased the growth of plants. In addition, straw extract also improved the positive effect of soil nutrients on shoot growth, probably because of its own nutrient content. Therefore, the FPCP pathogens could be more effective where more straw extract has accumulated.

Thirdly, increasing competition decreased seedling growth, and interaction between competition and straw extract improved the decrease, which indicates that densely populated patches of marsh reed grass are already inhibited by both competition and autoallelopathy. Addition of the FPCP pathogens caused further declines in growth in the presence of competition and straw extract, and could therefore be more effective in denser populations, i.e. grass with more competition.

In general, since higher soil nutrients, especially N, can greatly improve the plant growth in the presence of FPCP, fertile soils greatly limit the use of biological control agents, e.g. the FPCP pathogens, as herbicides. The speed of leaf damage is therefore a key determinant of success of the FPCP pathogens. If the speed leaf damage is greater than the speed of shoot growth, the resources produced by photosynthesis will suffer, which will lead to more damage of roots and shoots, i.e. the success of the FPCP pathogens will increase. On the other hand, if the speed of shoot growth is greater than leaf damage, more resources will be allocated to roots and shoots growth, which actually decrease the success of the FPCP. The results indicated that interactions between the three factors only suppress the growth of marsh reed grass, but do not kill it. Such non-lethal suppression plays an important role in making conifer seedlings free to grow, while limiting the negative effects of the ecosystem losing the grass entirely, since marsh reed grass can still provide beneficial effects in the forest.

Suggestions on future studies

Some other factors except autoallelopathy, competition and soil nutrients, should be studied in the future: 1) light can change resources allocation in above- and below-ground tissues; 2) Calcium is another nutrient in soil, and calcium affects the growth of one competitor, C.cpigejos, of the marsh reed grass, and other pathogens, such as some fungi; 3) temperature, humidity, and other environmental factors unrelated to soil, should be considered.

Five-sentence summary

Plant pathogens (i.e. some virus, fungi, or bacteria) can work as herbicides in the field, but their efficacy is limited by some environmental factors. The authors examined the influence of soil conditions and competition on marsh reed grass exposed to pathogens. They grew seeds of the grass in treatments with or without pathogensand estimated the effects of three additional factors: straw extract (i.e. extract from the grass) addition vs. competition; straw extract vs. nutrient-addition; and competition vs. nutrient-addition. They found that high concentration of straw extract and high levels of competition improved the role of pathogens as herbicides, but high nutrients levels tended to decrease such a role. They concluded that these pathogens could be more effective where more extract has accumulated or in denser populations of the grass, and that these pathogens only suppress the growth of the grass, but not kill it..


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)