Elsevier

Scientia Horticulturae

Volume 274, 15 December 2020, 109674
Scientia Horticulturae

Quantitative leaf anatomy and photophysiology systems of C3 and C4 turfgrasses in response to shading

https://doi.org/10.1016/j.scienta.2020.109674Get rights and content

Highlights

  • Turf quality and growth characteristics in both C3 and C43 and C4 turfgrass show differences under shade.

  • Shading causes the shrinkage of leaves for both turfgrass by reducing leaf thinkness, and increases the vascular bundle in leaves of C44.

  • Special leaf anatomical structure and photochemical properties may contribute to better shade tolerance turfgrass.

Abstract

  • Understanding the differences between C3 and C4 turfgrasses to shade are crucial for turfgrass maintenance and future shade tolerance breeding. The objectives of this study were to compare and analyze shade tolerance mechanism of both C3 and C4 turfgrasses in turf performance, growth, tissues and physiological aspects. Species Poa supina ‘SupraNova’ (C3 grass), and Stenotaphrum secundatum ‘S5′ (C4 grass) were subjected to a gradient of shading levels of 34.7 %, 69.8 %, 92.3 % and the control group CK (un - shaded). Visual turf quality (TQ) and turf color intensity (TCI) exhibited lower in S5compared to SupraNova on most testing days. S5 tended to have greater total biomass (TB), above- and below-ground biomass (AGB, BGB) under the 34.7 % shading level in contrast to SupraNova, whereas the ratio of above- to below-ground biomass (RAB) was higher in SupraNova. The average daily growth rate (ADGR) of both turfgrasses increased first, then declined during the shade periods, however, SupraNova under shading levels of 69.8 % and 92.3 % grew poorly than S5. The lowest ratio of Chlorophyll a/b showed under 34.7 % shade but the decreases of the ratio were different with S5 decreased by 40.5 % and SuperNova decreased by only 2.2 % compared to controls. Light shading (34.7 %) caused the qP, ETR and Fv/Fm increased greatly for both species, while severe shading induced higher qP, ETR and Fv/Fm in S5 than in SupraNova. Severe shading also caused more severe alterations in the leaf anatomical structure of SupraNova compared to S5. Our results indicated that 34.7 % shading is more favorable for the normal growth of two species. The promoted biomass and TQ of S5 may due to higher photochemical efficiency and unique leaf Kranz structure under severe shading.

Introduction

Light is an essential ecological factor affecting plant survival, growth, and development (Gardner et al., 2013). When the light environment changes, vegetation responds through various adaptive mechanisms with respect to their morphology, tissue structure, photosynthetic characteristics, and other plastic properties of plants (Olsrud and Michelsen, 2009). Adaptability to a light environment varies widely among plant species (Huang et al., 2011), and even within species, individuals at different developmental stages can differ in their reaction to a changed light environment. Severe light intensity probably causes photoinhibition including photobleaching and chlorosis followed by reduced photosynthetic efficiency (Navas and Garnier, 2002; Špudoa et al., 2005; Jung et al., 2020). Light intensity can be reduced by 95 % because of shaded caused by buildings, clouds, and different colored shade objects, leading also to changes in the quality of the light that reaches the surface of turfgrasses (Beard, 1969). It is estimated that 20–25 % of all turfgrasses are maintained under some degree of shade in urban areas (Almodares and Beard, 1978), but most of the turfgrass species used are not well adapted to shade (Winstead and Ward, 1974). Shade can influence the physiological, morphological, and anatomical characteristics of turfgrass by altering the intensity, quality, and duration of light (Wherley et al., 2005).

Turfgrass species are usually divided into cool-season and warm-season turfgrasses. Cool-season turfgrass is commonly adapted to temperate and subarctic climates and thus features cold hardiness (Shah et al., 2017; Chen et al., 2018), while warm-season turfgrasses are used specially in tropical and subtropical areas where their heat tolerance enhances their performance with turf quality (Turgeon, 2012). Most of the cold-season turfgrasses are referred to as C3 plants, since their carbon fixation by photosynthesis occurs primarily via the C3 pathway, but this carbon assimilation normally happens through the C4 cycle (C4 plants) in warm-season turfgrasses (Beard, 1998). In general, cool-season turfgrass has a low light compensation and light saturation point, which makes cool-season turfgrass more shade tolerant but less photosynthetic efficient when light is limited as warm-season turfgrass (Kephart et al., 1992). Research on C3 and C4 plants has shown distinguished differences between them in their tissue structure and photosynthetic characteristics (Still et al., 2003; Ravilious et al., 2012; Lundgren et al., 2019).The most distinguished attribute of C4 grasses is their specific leaf anatomy, called “Kranz anatomy” (Lundgren et al., 2014; Sage et al., 2018), comprising a single layer of large, photosynthetically active bundle sheath cells with more abundant chloroplasts surrounded by a tight layer of mesophyll cells (Dengler and Nelson, 1999; Edwards and Voznesenskaya, 2011). In comparison, there are no chloroplasts in bundle sheath cells of C3 grasses and cells size are small surrounded by loose mesophyll cells (Beard, 1972). Because of their specific cellular structure, photosynthesis in C4 plants occurs in both vascular bundle sheath cells and mesophyll cells, whereas C3 grasses rely on mesophyll cells only for photosynthesis (Kumar and Kellog, 2019). Accordingly, C4 plants are more efficient in CO2 assimilation and light energy utilization under the same light condition when compared to C3 plants, although C4turfgrass is more sensitive to shade than C3 turfgrass (Kephart et al., 1992; Sage and McKown, 2006; Sage et al., 2018). Leaves of plants have strong plasticity, enabling them to maximize their ability to capture both diffuse and direct light (Shad et al., 2016). When light becomes the main factor limiting the development of the plant, its leaves will adapt to this stress by changing their shape and structure, such as leaf thickness and the density of veins (Poorter and Bongers, 2006; Hu et al., 2011).The mechanisms of plant leaf anatomy and photophysiology in C3 and C4 plants in adverse environments have been extensively studied (Stier, 2007; Ripley et al., 2007; Jiang et al., 2011; Zienkiewicz et al., 2015; Killi et al., 2017). Yet, for turfgrass, studies that compare different adaptabilities and changes between C3 and C4 types under light limiting conditions are lacking.

Chlorophyll a fluorescence reflects plant performance of the photosynthetic apparatus (Zhong et al., 2014; Zhang et al., 2016; Yang et al., 2017), and dissipates excess light energy absorbed by leaf pigments as heat or as re-emission (Stirbet et al., 2018). The most widely used parameters of chlorophyll a fluorescence in relation to light-use efficiency and abiotic stresses are the following: Fv/Fm, representing the maximum quantum yield of primary PSII photochemistry; qP, photochemical quenching coefficient; qN, non-photochemical quenching coefficient; and ETR, electron transfer rate (Strasser et al., 2010; Wang et al., 2014; Kalaji et al., 2016; Guidi et al., 2019). Proper shading favoures the photochemical efficiency and protects the photosynthetic apparatus (Terashima et al., 2001; Micco et al., 2019). However, excessive shading can negatively affect on leaf chlorophyll (Chl), one of the most important factors determining the light-use efficiency (Ghosh et al., 2004; Mao et al., 2007). Low light reaching the plants diminish their rates of photosynthesis by reducing the Chl content, particularly of Chl a which is more directly involved in determining the processes of photochemical and non-photochemical quenching (Sestak, 1996; Dai et al., 2009). Studies have shown that shading can change a plant Chl a, Chl b, and total Chl content as well as Chl a/b value (Mendes et al., 2001; Gulmira et al., 2007; Zhang et al., 2017). However, how C3 and C4 turfgrasses respond to shade conditions in terms of plant anatomical structure, photosynthetic physiology, and turf performance are not well understood. More knowledge of these responses could provide fresh insights into plant shade-tolerance mechanisms, as well as genetic tools to modify desirable shading tolerance traits for improving cultivars of C3 and C4 turfgrasses in the future (Almodaresand Beard, 1978; Gardneret al., 2013).Therefore, the objective of this study was to investigate the turfgrass performance, growth, leaf anatomy, and photophysiology responses to shade of two species, Supina bluegrass (Poa supina Schrad., a C3 plant) and St. Augustine grass (Stenotaphrum secundatum [Walt.] Kuntze., a C4 plant). These two grass species are widely used in sports fields and are generally considered the most shade tolerant in their respective C3 and C4 groups.

Section snippets

Plant materials and cultivation

‘SupraNova’ (P. supina) is a European-bred variety provided by British Seed Houses, UK, and ‘S5′ (S. secundatum) is a wild accession native to Guangxi, China, which was supported by lab of turfgrass breeding in Hainan University. Sods (10 cm diameter) of each species were collected from 2-year-old turfgrass plots at the Horticulture Research Centre of Northeast Agricultural University (126°68′E, 45°72′N), in Harbin, China. For each species, 60 stem segments (≈ 4 cm each) were cultivated in a

Visual turf quality (TQ) and turf color intensity (TCI)

Based on the statistical analysis of variance, the interaction effect of species × shading (P < 0.05) on the changes of TQ and TCI was significant. Shading regimes significantly affected TQ and TCI in two species on measuring dates (Table 1). Light shading (34.7 %) can promote the TQ and increase the leaf TCI for both SupraNova and S5. During the first week of shading, TQ and TCI were not significantly different among the four treatments of two species. However, TQ and TCI varied between the

Discussion

For grass plants, shade can significantly alter their developmental processes. Grass plants will adopt an upright growth habit in response to reduced sunlight, thereby becoming less dense (Almodares and Beard, 1978; Cardillo and Bernal, 2006). We examined the TQ, leaf anatomical structure, and photochemical properties of the two grass species (SupraNova and S5) in response to shading. Light is the key factor affecting plant growth and insufficient light conditions can impede plant growth (Wang

Conclusion

Based on the results of this study, the TQ, TCI, growth, leaf anatomy and photochemical properties of Poa supina ‘SupraNova’ (C3 grass) and Stenotaphrum secundatum ‘S5′ (C4 grass) were influenced by shade, and exhibited significant differences between two species. Compared to SupraNova, S5 showed lower TQ, TCI and RAB on most testing days, while higher in AGB and BGB. The shading levels of 69.8 % and 92.3 % seriously decreased the ADGR of SupraNova indicated by poorly TQ and TCI as well as the

CRediT authorship contribution statement

Fuchun Xie: Writing - original draft, Visualization, Investigation, Software, Validation. Zhenjie Shi: Methodology. Gaoyun Zhang: Methodology. Cuiting Zhang: Methodology. Xiaoyang Sun: Software, Data curation. Yu Yan: Software, Data curation. Wei Zhao: Software, Data curation. Zhixin Guo: . Lu Zhang: . Shah Fahad: Conceptualization, Writing - original draft, Writing - review & editing. Shah Saud: Conceptualization, Writing - review & editing. Yajun Chen: Conceptualization, Supervision, Writing

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgments

This research was supported by National Natural Science Foundation of China (Project No. 31971772) and the College Student Innovation and Entrepreneurship Training Program of China (No 201910224035). We are grateful to Dr. Alex Burgon and Prof. Ziyong Wang for providing grass seeds. And we are also very appreciate to the editor and anonymous reviewers for their comments that helped to greatly improve the manuscript.

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