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      A comparative study on seed heteromorphism in Achnatherum brachychaetum (Godr.) Barkworth and Nassella clarazii (Ball) Barkworth

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      PamelaLernerThesis.pdf (388.2Kb)
      Date
      2005-12-15
      Author
      Lerner, Pamela Diana
      Type
      Thesis
      Degree Level
      Masters
      Metadata
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      Abstract
      Seed heteromorphism related to chasmogamous (CH) and cleistogamous (CL) seeds can have different ecological significance in species with different functional characteristics, competitive ability and palatability. Punagrass [Achnatherum brachychaetum (Godr.) Barkworth], an invasive, perennial grass is common in grasslands of Argentina and it is an aggressive weed in other parts of the world. Flechilla grande [Nassella clarazii (Ball) Barkworth] is a palatable perennial grass associated with the dominant "climax" vegetation in grasslands of Argentina. Seeds of the two grasses were collected from grasslands of Argentina, and growth chamber and greenhouse experiments were conducted to determine: 1) germination, dormancy breaking, and mass of CH and CL seeds of the two species 2) effects of contrasting range condition on germination and seed mass of punagrass, 3) the relative fitness of plants from CH and CL seeds, 4) if contrasting range condition affect fitness of CH plants of punagrass, and 5) the effect of maternal nutrient environments on CH and CL seeds and on fitness in the two species. Small CH seeds of high dispersal potential were less dormant than large CL seeds of low dispersal potential in punagrass. CH and CL seeds of flechilla grande had similar mass, germination, and response to dehulling. CL seed size and CL seed production of punagrass increased with good range condition. Increasing the maternal, nutrient environment enhanced germination of CH seeds, CL seed size, growth rate, development, biomass and seed production more in punagrass than flechilla grande. Under low nutrient conditions, flechilla grande produced a few large CH seeds. CH progeny of punagrass grew fast and developed rapidly as compared to CL progeny, which in turn produced many CH seeds. CH and CL seeds of flechilla grande had similar contribution to the fitness of adult plants. In both species, the ecological significance of having seed heteromorphism is that sibling competition is probably reduced by having more diverse offspring. Heavy grazing of competitive species such as flechilla grande may favours species as punagrass with many small CH seeds, high potential for colonization as well as large CL seeds for persistence in the seed bank and seedling competition.
      Degree
      Master of Science (M.Sc.)
      Department
      Plant Sciences
      Program
      Plant Sciences
      Supervisor
      Bai, Yuguang
      Committee
      Romo, James T.; Légère, Anne; Coulman, Bruce E.
      Copyright Date
      December 2005
      URI
      http://hdl.handle.net/10388/etd-01032006-144657
      Subject
      reproductive strategies in grasses
      Stipa
      reproductive allocation
      colonization/competition strategies
      adaptations for partitioning limiting resources
      seed size
      seed dormancy
      cleistogamy
      chasmogamy
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      • Electronic Theses and Dissertations
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