Abstract
BackgroundPhenotypic plasticity of fitness-related traits is vital for plant species to adapt to variable environments. Chenopodium glaucum L. and Amaranthus retroflexus L. are two common weed species globally. Understanding the plasticity in life-history traits, especially in reproductive allocation, within and among these species is important for predicting their success and for managing them in different environments.Methodology/Principal FindingsSeeds of the two plant species were sown every 10 days from 26 Jun to 15 Aug. Life-history and fitness-related traits of both phenology and morphology were measured, and dry biomass of roots, stems, leaves, and reproductive tissues was determined at physiological maturity. Length of reproductive and total life period of the two species differed among six sowing-date treatments. Later germinating plants led to relatively reduced total life period, size, and earlier reproduction than earlier germinating plants. The ratio of reproductive biomass to total plant biomass increased with later planting dates in C. glaucum but declined in A. retroflexus. Mature plant height, crown diameter, and reproductive tissue biomass, and seed production of C. glaucum and A. retroflexus increased with delayed reproductive period. Both species displayed true plasticity in reproductive allocation. However, the sowing date had a far greater effect on rate of vegetative growth than on allocation to reproduction.Conclusions/SignificanceThe fitness of both C. glaucum and A. retroflexus populations have an apparent increase when the period between germination and seed production is much longer. However, C. glaucum appears better adapted to later sowing than A. retroflexus. Controlling seedlings prior to reproduction will alleviate the negative effect not only in the present year but also in future years.
Highlights
Phenotypic plasticity and fitness-related traits are of vital significance for plant species to adapt to [1,2] or tolerate heterogeneous environments [3,4,5]
Chenopodium glaucum and A. retroflexus seeds sown on June 26 and July 6 emerged 1 to 2 d later than later sown seeds (Table 1)
Vegetative period was substantially reduced with later sowing date and ranged from 52 to 24 d in C. glaucum and from 37 to 28 d in A. retroflexus
Summary
Phenotypic plasticity and fitness-related traits are of vital significance for plant species to adapt to [1,2] or tolerate heterogeneous environments [3,4,5]. True plasticity in allocation was defined as a change in the allometric relationship itself, rather than a change in the rate of growth They argued that true plasticity can only be determined when individual plant reproductive biomass is related to vegetative biomass, as opposed to analyzing biomass ratios, because the former accounts for differences in the size among individuals resulting from multiple factors occurring during growth [13]. Further understanding of plasticity in life-history traits, especially on reproductive allocation, among species is important for predicting their success in different environments. Understanding the plasticity in life-history traits, especially in reproductive allocation, within and among these species is important for predicting their success and for managing them in different environments
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