Abstract
Clonal plants could modify phenotypic responses to nutrients heterogeneously distributed both in space and time by physiological integration. It will take times to do phenotypic responses to modifications which are various in different growth periods. An optimal phenotype is reached when there is a match between nutrient conditions and foraging ability. A single plantlet of Buchloe dactyloides with two stolons was transplanted into heterogeneous nutrient conditions. One stolon grew in homogeneous nutrient patch, while the other cultured in different scales of heterogeneous nutrient patches. As compared to the other nutrient treatment, heterogeneous nutrient treatments with small scale of 25×25 cm resulted in a higher biomass, and larger number of ramets, clumps and stolons in B. dactyloides at both genet and clonal fragment levels. Significant differences of number of ramets, clumps and stolons were detected at the rapid growth stage, but not in the early stage of the experiment. Foraging ability was more efficient in heterogeneous than in homogeneous nutrient conditions as assessed by higher root mass and root to shoot ratio. Different nutrient treatments did not prompt significant differences in internode and root length. Physiological integration significantly increased biomass, but did not influence other growth or morphological characters. These results suggest that physiological integration modifies phenotypic plasticity of B. dactyloides for efficient foraging of nutrients in heterogeneous nutrient conditions. These effects are more pronounced at genet and clonal fragment levels when the patch scale is 25×25 cm. Time is a key factor when phenotypic plasticity of B. dactyloides in heterogeneous nutrient conditions is examined.
Highlights
The availability of nutrients in natural habitats occurs at a variety of spatial and temporal scales
The number of ramets, clumps and stolons significantly increase as time progressed, and the significant differences were found among the four nutrient treatments at different times (Fig. 2, Table 1), the number of ramets and clumps differed on the 7th, 14th, 42nd and 49th days while the number of stolons differed on the 14th, 35th and 49th days (Table 2)
At the end of the experiment, the number of ramets, clumps and stolons were higher in the heterogeneous (T1, Treatment 2 (T2) and Treatment 3 (T3)) than in the homogeneous nutrient treatments (T4), but no significant differences were observed among the three heterogeneous nutrient treatments (Fig. 2A, B, C)
Summary
The availability of nutrients in natural habitats occurs at a variety of spatial and temporal scales. Physiological integration is one of the most important traits of clonal plants as it can optimize the resource allocation among modules of the whole plant It allows transporting photosynthates, water, nutrients, and signals via connected stolon or rhizome internodes from source modules to sink modules of the same genet [14,15]. De Kroon and Hutchings [34] indicated that increased branching in favorable conditions could be interpreted as a positive growth response. Plants might shorten their internodes to form the clumping ramets in order to maximize the acquisition of required nutrients in a local environment under favorable conditions. Physiological integration among ramets modified morphological, physiological and mycorrhizal plasticity of roots to allow locating more roots in favorable patches to maximize the nutrient acquisition from heterogeneous habitats [35,36,37,38,39,40]
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