Kentucky bluegrass (KB, Poa pratensis) is one of the most widely used cool-season turfgrass species, but it is sensitive to drought stress. Molecular studies in KB are hindered by its large and complex genome structure. In this study, a comparative transcriptomic study was conducted between a short and long period of water deficiency. Three transcriptome libraries were constructed and then sequenced by using leaf RNA samples of plants at 0, 2, and 16 h after PEG6000 treatment. A total of 199,083 differentially expressed genes (DEGs) were found. The Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed that DEGs were enriched in “Plant hormone signal transduction” and “MAPK signaling pathway-Plant”. Some key up-regulated genes, including PYL, JAZ, and BSK, were involved in hormone signaling transduction of abscisic acid, jasmonic acid, and brassinosteroid and possibly these genes play important roles in coping with drought stress in KB. Furthermore, our results showed that the concentrations of ABA, JA and BR increased significantly with the extension of the drought period. The specific DEGs encoding functional proteins, kinase and transcription factors, could be valuable information for genetic manipulation to promote drought tolerance of KB in the future.

Turfgrasses used on golf courses, sports fields and in urban landscapes have significant ecological and economic values. Various abiotic stresses are crucial in limiting the growth and development of turfgrass. As an important amino acid metabolite, proline can act as a signal to trigger plant responses to stress. Proline accumulation is not only a stress signal, but also alleviates plant damage by maintaining photosynthesis and the activities of antioxidant enzymes and the levels of non-enzymatic antioxidant compounds, thus reducing reactive oxygen species content, and regulating osmosis. A better understanding of mechanisms of proline response to abiotic stress in turfgrass is vital for the development of stress-tolerant germplasm. This review summarizes research progress into the role of proline in regulating growth and physiological and molecular adaptations to abiotic stress, with emphasis on drought, salt and temperature tolerance.

Rapid rise in temperature in summer causes severe injury to cool-season turfgrass of both native species and introduced ones in Heilongjiang of Northeast China. The objectives of this study were to compare physiological responses to seasonal heat stresses and turf performances between native and introduced commercial Poa accessions. Three Chinese native Poa species (i.e., P. pratensis, P. sibirica and P. sphondylodes) and three USA Kentucky bluegrass cultivars (ie. ‘Midnight’, ‘Moonlight’ and ‘BlueChip’) were evaluated under field conditions in 2017 and 2018. All accessions showed unique characteristics and considerable seasonal differences in response to temperatures. However, performances over all accessions were largely similar in early spring and autumn. In summer, native P. pratensis performed similar to ‘Midnight’, ‘Moonlight’ or ‘BlueChip’, with respect to such traits or parameters as quality, coverage, color intensity, growth rate, osmolytes, ROS and anti-oxidant production. Native P. pratensis could be used as a new turf resource for further improvement and application under the specific climatic conditions in Heilongjiang; native P. sphondylodes may be used in repairing damaged environments or for alternative seasonal greenness.

Understanding the effect of water heterogeneity on the growth and water integration of clonal plants is important for scientific water management. In controlled field plots, we conducted a study by creating three different soil water treatments comprising four patches with different soil water supplies using Kentucky bluegrass (Poa pratensis L.) as the materials. The objective was to explore the differences in the growth indices and morphological attributes, and the possible water integration in ‘Arcadia’ Kentucky bluegrass in plots and patches with different soil water availabilities. Soil water deficit resulted in the declined biomass, root/shoot ratio and leaf relative water content of the whole genet, decreased leaf length and height of mother ramet, reduced leaf width and height of daughter ramets, and significant changes in the structures of vascular bundles in rhizomes and leaves. However, the leaf length, leaf width, height and leaf relative water content of daughter ramets in heterogeneous water-poor patches were recovered to the levels in water-rich patches. In addition, the diameter of the vessel in the xylem and percentage of the xylem area in leaf vascular bundles of daughter ramets in the heterogeneous water-poor patch were insignificantly different from those in water-rich patches. These results demonstrated that water integration among interconnected ramets promoted the growth status of daughter ramets in heterogeneous water-poor patches. However, the water translocation in interconnected ramets subjecting to heterogeneous water supplies was not investigated using stable isotope labelling in this study. Thus, the directions and patterns of water translocation among ramets necessitate further research.

Bermudagrass (Cynodon dactylon) is a widely used warm-season turfgrass worldwide. However, bermudagrass often faces the challenges from drought stress in practical application. Selection and breeding of drought-tolerant cultivars of bermudagrass is crucial for thriving in arid environments. In this study, we employed two different drought-tolerant bermudagrass cultivars ‘Yangjiang’ and ‘Guanzhong’ to assess the morphology, physiology and transcriptome under various drought stress conditions. The outcomes unveiled that drought-tolerant ‘Guanzhong’ exhibited superiority in morphology, light utilization efficiency, relative water content, antioxidant and osmotic regulation capabilities compared to drought-susceptible ‘Yangjiang’. In addition, transcriptome sequencing showed that photosynthesis, amino acid metabolism, peroxisome and plant hormone signal transduction pathways were the key metabolic pathways of bermudagrass in response to drought stress. Compared to the drought-sensitive cultivar ‘Yangjiang’, the drought-tolerant ‘Guanzhong’ exhibited lower expression of AUX/IAA genes (negative regulators of auxin signaling), which reduces their inhibitory effect on auxin response factors (ARF), thereby enhancing auxin signaling efficiency to coordinate adaptive growth. Additionally, compared with ‘Yangjiang’, the down-regulated protein phosphatases (PP2C) in ‘Guanzhong’ weaken their suppression of SnRK2, resulting in heightened ABA signaling sensitivity. In comparison to ‘Yangjiang’, ‘Guanzhong’ displayed a higher IAA concentration and a lower ABA concentration under stress conditions, thus ensuring a more efficient utilization of water by minimizing stomatal aperture and reducing water evaporation. The results suggested that regulation of morphology, physiological metabolism and genes expression could contribute to drought tolerance in bermudagrass.

Perennial ryegrass (Lolium perenne L.) is a popular and important cool-season turfgrass used in parks, landscapes, sports fields, and golf courses, and it has significant ecological, environmental, and economic values. It is also widely used as forage and pasture grass for animals around the world. However, the growth of perennial ryegrass is often affected by various abiotic stresses, which cause declines in turf quality and forage production. Among abiotic stresses, drought, salinity, temperature, and heavy metal are the most detrimental factors for perennial ryegrass growth in different regions, which result in growth inhibition, cell structure damage, and metabolic dysfunction. Many researches have revealed a lot useful information for understanding the mechanism of tolerance to adverse stresses at morphophysiological level. In this chapter, we will give a systematic literature review about morphological and physiological changes of perennial ryegrass in response to main stress factors and provide detail aspects of improving perennial ryegrass resistance based on research progress. Understanding morphophysiological response in perennial ryegrass under stress will contribute to improving further insights on fundamental mechanisms of perennial ryegrass stress tolerance and providing valuable information for breeding resistance cultivars of perennial ryegrass.