Phenotypic Plasticity in Sexual Reproduction Based on Nutrients Supplied From Vegetative Ramets in a Leymus chinensis Population

Abstract

Phenotypic plasticity is considered a major mechanism that allows plants to adapt to heterogeneous environments. The physiological integration between the interconnected rhizomes or stolons of clonal plants influences the plasticity of such plants in heterogeneous environments. However, the determinants of plasticity of reproductive ramets in clonal plants in homogeneous environments are unclear. Here, we chose Leymus chinensis, a perennial rhizomatous grass, and conducted a series of field experiments in situ, including grading sampling of reproductive ramets and different connection forms of vegetative ramets labeled with 15 N at four reproductive stages. Reproductive ramet biomass, inflorescence biomass, seed number, seed-setting percentage, reproductive allocation, and reallocation significantly increased with an increase in the number of vegetative ramets connected to tillering nodes, and the plasticity indexes of these six phenotypic characteristics showed similar increasing trends. The amount of nutrients supplied from the connected vegetative ramets to the reproductive ramets was significantly affected by the transfer direction, reproductive stage, and position order of the vegetative ramets. Throughout the sexual reproduction stage, nutrients were preferentially transferred to the acropetal reproductive ramet in L. chinensis populations. The amount of nutrients supplied from the connected vegetative ramets to the reproductive ramets at the milk-ripe stage, when sexual reproduction was most vigorous, was significantly larger than that at other reproductive stages. The amount of nutrients supplied from the spacer vegetative ramet to the acropetal reproductive ramet was significantly larger than that to the basipetal reproductive ramet. The closer the vegetative ramet was to the reproductive ramet, the more nutrients were supplied; the amount of nutrients supplied was significantly negatively related to the position order of the vegetative ramet. We identified the determinant of plasticity in sexual reproduction in clonal plants in a homogeneous environment: physiological integration between ramets within clones. Our results are vital for better understanding the adaptation of populations and even the evolution of species of clonal plants.

Physiological Integration Increases Sexual Reproductive Performance of the Rhizomatous Grass Hierochloe glabra

“…H. glabra is a typical early spring grass, with its seed maturing in early June and approximately one and a half months earlier than L. chinensis . In the present study, in the natural populations of H. glabra , we found that vegetative ramets connected to tillering nodes could translocate their own resources to reproductive ramets through tillering nodes for seed production, which is highly consistent with the findings in L. chinensis [ 55 ]. This implies that there is an evident commonality between H. glabra and L. chinensis ; namely, during sexual reproduction, there is the physiological integration between different functional ramets connected by tillering nodes.…”

“…In this study, in the natural populations of H. glabra growing in relatively homogenous sandy soil ( Supplementary Table S7 ), we found that a reproductive ramet connected to two vegetative ramets had an average of 1.2 more seeds and 0.9% greater seed-setting rate than that connected to one vegetative ramet in 2018 ( Figure 1 A,C). In the same year, our research group investigated the sexual reproductive characteristics of L. chinensis growing in homogenous sandy soil in this study area and found that a reproductive ramet connected to two vegetative ramets had an average of 2.5 more seeds and 5.2% greater seed-setting rate than that connected to one vegetative ramet [ 55 ]. By this token, H. glabra had a lower capacity for physiological integration than L. chinensis .…”

“…The annual mean temperature ranges from 4.6 °C to 6.4 °C, and the annual mean precipitation varies from 300 mm to 450 mm. The frost-free period lasts approximately 130–165 days [ 55 ].…”

Genetic structure in patchy populations of a candidate foundation plant: a case study ofLeymus chinensis(Poaceae) using genetic and clonal diversity

“…Mean annual precipitation ranges from 300 to 450 mm, more than 60% of which occurs from June to September. Mean annual temperature ranges from 4.6 to 6.4°C and the frost-free period lasts for 130 to 165 days (Guo et al, 2020). The soil is a mixed salt-alkali meadow steppe (Salid Aridisol, US Soil Taxonomy) with 29% sand, 40% silt and 31% clay (top 10 cm) (Zhu, 2004).…”

The Intensity of Simulated Grazing Modifies Costs and Benefits of Physiological Integration in a Rhizomatous Clonal Plant

“…Tzvel. L. chinensis was selected as the study species for this experiment because it is a typical rhizome clonal plant, and is often exposed to grazing and mowing due to its good palatability for livestock [35,36]. Consequently, it is always subject to nutrient heterogeneity and herbivory-induced heterogeneity.…”