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

Understanding the differences between C-3 and C-4 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 C-3 and C-4 turfgrasses in turf performance, growth, tissues and physiological aspects. Species Poa supina 'Suprallova' (C-3 grass), and Stenotaphrum secundatum 'S5' (C-4 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 Suprallova 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 Suprallova, whereas the ratio of above- to below-ground biomass (RAB) was higher in Suprallova. The average daily growth rate (ADGR) of both turfgrasses increased first, then declined during the shade periods, however, Suprallova 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 Suprallova. Severe shading also caused more severe alterations in the leaf anatomical structure of Suprallova 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.