Dafu Yu

The bud bank of perennial grasses is a controlling factor in population dynamics and is estrongly affected by soil water and nitrogen status. To explore how the bud bank size and its components affect shoot population density under different soil moisture and nitrogen contents in spring and autumn. A three-full-factorial field experiment with factors of treatment timing (spring and autumn), nitrogen rate (control and 10 g N m⁻² yr⁻¹) and irrigation rate (control and +40 mm rainfall) was conducted in Leymus chinensis (a C₃ plant) in the northeast of China. The number of two types of buds (axillary shoot bud and rhizome bud), shoot population density, soil properties and rhizome traits (rhizome length and rhizome number) were determined to explore what and how changes in bud bank composition influences shoot population density in spring and autumn. The results showed that: (1) Regardless of the irrigation and nitrogen application timing, the simultaneous irrigation and nitrogen application significantly increased the number of two types of buds and promoted the shoot population density in spring and autumn by 56.75% and 47.74%, respectively. (2) The bud bank was dominated by rhizome buds in spring under control and dominated by axillary shoot buds under the combined irrigation and nitrogen treatment in autumn. Axillary shoot bud was the determining component in the population density increases in both spring and autumn, which were significantly associated with soil available phosphorus, available nitrogen and rhizome length and number. In summary, the number of different buds was strongly impacted by irrigation and nitrogen application at the crucial bud-bank formation stage. Agronomically, the forage yield could be largely increased through the increase in the axillary shoot bud density by using irrigation and nitrogen application in L. chinensis and other rhizomatous perennial grasses.

Ryegrass has a relatively high salt tolerance and is considered to be a promising species for both foraging and turf purposes in salt-affected soils in China. While annual ryegrass and perennial ryegrass are two different species, they have similar genomes. However, little is known about their physiological and molecular response mechanisms to salinity stress. Here, biomass, chlorophyll fluorescence, and inorganic ion and organic solute content were measured. 2-DE-based proteomic technology was then used to identify the differentially expressed proteins in the salt-treated seedlings. The results showed that salt stress reduced growth and photosynthesis in the seedlings of both species, but much more so in annual ryegrass. With increasing salinity, the Na⁺ concentration increased while the K⁺ concentration decreased in both species, and the sugars and proline increased as the primary organic solutes used to cope with osmotic stress. Additionally, proteomic analysis revealed 33 and 37 differentially expressed proteins in annual and perennial ryegrass, respectively. Most of the identified proteins were involved in carbohydrate and energy metabolism, photosynthesis, genetic information processes, amino acid metabolism, stress defense, and protein synthesis and folding. The results suggest that the two-ryegrass species had different physiological and proteomic responses. These findings can provide new insights into physiological mechanisms by which ryegrass species respond to salt stress.