Trinexapac-ethyl [4-(cyclopropyl-alpha-hydroxy-methylene)-3,5-diox ocy
clohexanecarboxylic acid ethyl ester] is a foliar-applied growth regul
ator for turfgrass that can reduce mowing frequency, clipping producti
on, and enhance turfgrass color. C-14-Trinexapac-ethyl was used to eva
luate absorption and subsequent C-14-trinexapac-ethyl translocation in
hydroponically grown 'Blacksburg' Kentucky bluegrass (Poa pratensis L
.). The magnitude and rate of' C-14 trinexapacethyl absorption by vari
ous organs was as follows: plant base > leaf blade > roots. Plant base
, as a morphological description and site of application, refers to th
e collection of leaf sheaths surrounding the compressed turfgrass stem
and the crown of the plant. Over the time period of 0 to 24 h, maximu
m absorption by the plant base was obtained in 8 h and by the leaf bla
de in 24 h. Absorption by the roots was negligible. Addition of an act
ivator organosilicone adjuvant, Sylgard 309, significantly enhanced C-
14-trinexapac-ethyl absorption by the leaf blade 1 h after application
but did not enhance absorption by the plant base. Of the C-14-trinexa
pac-ethyl absorbed by the plant base, over 50% was translocated to the
plant foliage after 24 h. Of the C-14-trinexapac-ethyl absorbed by th
e leaf blade, one-third was translocated after 24 h; the direction of
movement was predominantly basipetal. Less than 5% of absorbed C-14-tr
inexapac-ethyl from either site was translocated to roots or to rhizom
es with daughter plants, explaining the lack of inhibition of lateral
turfgrass growth. Combined effects of enhanced leaf blade absorption,
basipetal translocation from the leaf blade, and acropetal translocati
on from the plant base of C-14-trinexapac-ethyl helped explain the pos
itive impact of Sylgard 309 on efficacy and rainfastness of trinexapac
-ethyl.