Anatomical Responses of ‘Merion’ Kentucky Bluegrass and ‘Pennlawn’ Red Fescue at Reduced Light Intensities1

Abstract

The objectives were to characterize the anatomical responses of Kentucky bluegrass and red fescue to reduced light intensities. Kentucky bluegrass (Poa pratensis L. ‘Merion’) and red fescue (Festuca rubra L. ‘Pennlawn’) were grown in separate growth chambers at light intensities of 2.7, 10.8. and 43 klux. Light quality, soil moisture, and soil temperature were standardized among chambers. Anatomical studies were conducted on the youngest, fully expanded leaf blade.Merion displayed a decrease in cuticle thickness and vascular and support tissues under reduced light intensities, whereas Pennlawn did not. Stomata density of both species decreased under reduced light. Stomata pore length of both species did not vary with light intensity.The number of chloroplasts/cross sectional unit area decreased with reduced light intensity for both species. Merion had increased thylakoid and grana stack development within individual chloroplasts at reduced light intensities, whereas Pennlawn chloroplast ultrastructure remained unchanged.Shade adaptation of Pennlawn may be related to more developed cuticle, vascular, and support tissue and to chloroplast ultrastructure. Stomata and chloroplast density responses of the two species to reduced light intensity were similar and could not be associated with the ability of Pennlawn to provide a more desirable turf in the shade than Merion.