Temperature Control of Physiological Dwarfing in Peach Seedlings

Publisher Website
Google Scholar
Abstract
Physiological dwarfing in peach seedlings from non-afterripened seeds has been considered by others to be the result of a growth inhibitor persisting from the resting seeds. However, this dwarfing factor never enters the axillary buds nor does it appear to be degraded or diluted during seedling growth. The present study was made using resting peach seeds [Prunus persica (L.) Batsch. cv. Elberta] permitted to germinate by removal of part of the seed coat and associated endosperm tissue. The expression of dwarfing symptoms during growth was found to be controlled by germination temperature during the 1st 2 or 3 to 8 or 9 days. Within this period, germination at 22[degree]C produced almost entirely normal plants; germination at 25[degree] resulted in severe dwarfing. Almost all of the affected organs were formed during or after the germination period. Other peach varieties responded in the same general way. Daily alternation between 25[degree] and 19[degree] (12 or 16 hr and 12 or 8 hr), or 2-day exposure at 25[degree] during a 9 day germination period at 19[degree], produced plants with less severe symptoms than those germinated at a constant 25[degree]. Treatment with gibberellin during germination did not alter temperature sensitivity. Imbibed seeds did not become temperature sensitive until removal of part of the seed coat permitted germination to begin: no sensitivity could be shown beyond the 9 day germination period. Afterripening seeds at 5[degree]C reduced the severity of dwarfing resulting from 25[degree] exposure, but did not shorten the sensitive period. The physiological and anatomical aspects of dwarfing suggest control by a self-duplicating system localized in a limited region of the apical meristem and transmitted only by cell division. This system is temperature sensitive during only a limited period of plant development.