Dependence of the detectability of stored growth on the elongation rate in IAA- and acid-induced elongation of wheat coleoptile sections

The detectability of stored growth at various elongation rates(IAA- and acid- induced) was investigated in 5-mm wheat coleoptilesegments. After 20 min turgor reduction by 0.15 M or 0.20 Mmannitol, the detectability of stored growth depended on theelongation rate before turgor reduction. A hypothesis was proposedthat the amount of stored growth is limited. Depending on theelongation rate, this then appears as complete or partial compensationof the growth lost during turgor reduction. The limit for fullcompensation was about 300 µm/hr?segment. At elongationrates of > 600 µm/hr?segment, no stored growth couldbe detected. The elongation of the wheat coleoptile sectionsat low and high elongation rates is assumed to be limited bydifferent rate-determining steps. (Received November 22, 1977; )