A mathematical model relating environmental temperatures to rest completion of 2 peach cultivars has been developed. The model equates temperatures to effective chill-units, such that, one can predict when rest will or has been completed with a high degree of accuracy.

A model has been developed that relates the stages of spring bud development of ‘Redhaven’ and ‘Elberta’ peaches (Primus persica (L.) Batsch) to an accumulation of growing degree hours following rest completion. The accumulation of growing degree hours is based on a lower limit of 4.5°C and an upper limit of 25°.

Temperature treatments influenced inception, intensity and termination of rest in peach trees [Prunus persica (L.) Batsch]. A substance that affected the response was translocated within the trees. The time of leaf abscission in the fall was related to duration and intensity of rest in ‘Gleason Elberta’ peach leaf terminal buds. An August application of 100 ppm gibberellic acid (GA3) and warm field temperatures delayed defoliation and extended rest.

Oats, flax and barley were spraved with varicus formulations of MCp (2-methyl-4-chlorophen-oxy-acetic atid) and 2,4-D (2,4-

Electron micrographs of ‘Gleason Elberta’ peach flower buds, Prunus persica (L.). Stobes, during rest indicated only moderate metabolic activity prior to December 20. In the December 27 collection, however, a single membrane-bound body (microbody or lysosome) and rough endoplasmic reticulum (RER) were present. Also, the Golgi bodies (dictyosomes) were nearly mature. Heterochromatin disappeared on January 3. By the end of February the number of mitochondria, Golgi bodies, and vesicles had increased markedly. During the first week of March, large nucleopores were observed in the nucleus. These data indicated that bud cells were changing at cold temperatures during winter. Organellar changes were compared to the predicted date for end of rest (13).