The independent assessment of frost hardiness of excised laminae, excised roots and trimmed tillers of tall fescue (Festuca arundinacea).
Trimmed tillers, excised roots and excised laminae of tall fescue were subjected to various temp. down to -12 deg C for various exposure times and at various cooling and warming rates. Damage to tillers was assessed by their regrowth over a period of 40 days. Damage to excised roots and excised laminae was assessed by a conductivity method. Excised laminae froze at about -3.3 deg and trimmed tillers froze at about -0.8 deg ; these temp. are above those at which significant damage occurred. Roots froze at about -0.5 deg , which was close to that which caused significant damage (-1 deg ). Laminae attached to potted plants froze at about -7.4 deg . Conductivity measurements suggested that there was a range of temp. over which leaf and root damage was only partial. Material grown in controlled-environment conditions (15 deg 12-h photoperiod, 450 mu Einsteins/m2s and 75% RH) was exposed to temp. below 0 deg for 45 min, with cooling rates between 8 deg /h and 12 deg /h and a warming rate of 20 deg /h. Excised roots suffered significant damage at -1 deg , excised laminae at -5 deg and trimmed tillers at -6 deg . Old laminae were slightly more damaged at -7 deg than were young laminae. Temp. just low enough to damage the tillers, so that they failed to survive for 40 days, only caused a small amount of tissue damage (as measured by conductivity) and the leaf sheaths could regrow for a short period. The results are used to compare the hardiness of different plant parts. The relevance of the methods to realistic assessments of frost hardiness of laminae, roots and tillers of tall fescue is discussed.