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

Jian Guo,Haiyan Li,Yunfei Yang

doi:10.3390/plants9111608

Abstract

Clonal plants usually reproduce asexually through vegetative propagation and sexually by producing seeds. Physiological integration, the translocation of essential resources between ramets, usually improves vegetative reproduction. However, how physiological integration affects sexual reproduction has been less studied in clonal grasses. Here, we chose Hierochloe glabra, a major early spring forage of the eastern Eurasian steppe, and conducted a series of field experiments, including sampling reproductive ramets connected by tillering nodes to different numbers of vegetative ramets and 15N leaf labeling of ramet pairs at the seed-filling stage. In the natural populations of H. glabra, vegetative ramets were taller, had more and larger leaves, and greater biomass than reproductive ramets. Except for reproductive ramet biomass, sexual reproductive characteristics significantly increased with an increase in the number and biomass of vegetative ramets connected to tillering nodes. 15N labeling showed that vegetative ramets supplied nutrients to reproductive ramets through tillering nodes. Overall, our results indicate that significant differences in morphological characteristics and biomass allocation underlie resources translocation from vegetative ramets towards reproductive ramets. Physiological integration between different functional ramets can increase sexual reproductive performance, which will be beneficial to population persistence in H. glabra.

Highlights

Environments are generally heterogeneous, and the availability of essential resources needed for plant growth, such as water, light, and nutrients, is commonly changeable at small spatial scales [1]
We found a significant positive correlation between five estimates of resource investment in sexual reproduction and the number and biomass of vegetative ramets connected to tillering nodes in natural populations of H. glabra (Figure 1A–E and Figure 3A–E)
In the present study, taking 2019 as an example, we found that the seed number, floret number, seed-setting rate, seed biomass, and panicle biomass of the reproductive ramets connected to three vegetative ramets were 10.8 times, 1.2 times, 9.0 times, 6.9 times, and 1.3 times, respectively, as great as those of the reproductive ramets connected to zero vegetative ramets (Figure 1A–E), indicating that the larger the number of vegetative ramets connected to the reproductive ramet was, the better the sexual reproductive performance was

Summary

Introduction

Environments are generally heterogeneous, and the availability of essential resources needed for plant growth, such as water, light, and nutrients, is commonly changeable at small spatial scales [1]. Physiological integration refers to the translocation and sharing of essential resources, such as water, mineral nutrients, and carbohydrates, between ramets through physical connections in the same individual [5,6]. Clonal plants can produce genetically identical and potentially physiologically independent individuals (called ramets) through vegetative propagation and seeds by means of sexual reproduction [15]. Some clonal plants are often thought to primarily rely on vegetative propagation to achieve natural population regeneration with infrequent recruitment from seeds [16,17], but sexual reproduction through seeds produces genetically diverse offspring that may be greatly

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