Use of the Third Youngest Leaf to Estimate Leaf Area in Kentucky Bluegrass1

Abstract

AbstractPeriodic, non−destructive data on the number of leaves, tillers, and emerged rhizomes are basic to the determination of turfgrass response to stress. Although the leaf area of turfgrasses is also markedly affected by stress, it is difficult and time−consuming to obtain without injury to the herbage.To determine if the leaf measurements of a specific leaf of each plant is correlated to the same leaf measurements for all leaves of that plant, leaf measurements were made on all leaves of individual Kentucky bluegrass (Poa pratensis L.) plants subject to stress treatments of a restricted root zone, competition from plants of a different cultivar, and 4 cm mowing height. The plants were grown in vermiculite in plastic pots. Two experiments were conducted in the greenhouse while a third was conducted in a growth chamber. Leaf length measurements involving the sheath were taken from the crown while lamina length measurements were taken from the junction of the leaf blade and the leaf sheath. Blade width measurements were made midway along the lamina length for unmowed grasses and 1 cm from the junction of the leaf blade and leaf sheath for grasses mowed at 4 cm.The correlation coefficients for the leaf (sheath and blade) length (r ≥ 0.86), blade length (r ≥ 0.86), and blade width (r ≥ 0.92) of the third youngest leaf and the same measurements for the total leaf length of each shoot of ‘Birka’, ,‘Nugget’, ‘Sydsport’, and ‘Touchdown‘ were found to be highly significant. The γ values were highly significant. when the same measurements were made on Touchdown plants regularly mowed at 4 cm and on unmowed Nugget plants growing in competition with ‘A−34’ Kentucky bluegrass.Leaf measurements of the third youngest leaf can be used to estimate growth responses of Kentucky bluegrass plants which result in changes in leaf area. Blade measurements of intact turfgrass plants in a sward are useful to estimate changes in leaf area as they are easily obtained and result in little injury to the herbage.