Effects of Oxygen and Respiratory Inhibitors on Induction and Release of Dormancy in Aerial Tubers of Begonia evansiana

Abstract

Effects of 02 and some respiratory inhibitors on the induction and release of bud dormancy were examined with the aerial tubers of different ages of Begonia evansiana Andr. Oxygen was needed not only for tuber sprouting but also during the chilling process at 2 to 5 C to break tuber dormancy. If the mature tubers were exposed to blue light during the chilling period, their dormancy was strikingly released even by the chilling given under an 02 concentration as low as 3%. Blue light pretreatment promoted photo-sprouting of immature tubers only when given under lower 02 concentrations. On the other hand, red light became effective in inducing dormancy in the immature tubers and in prolonging dormancy in the mature tubers as 02 tension was increased. This was also the case with the induction of dormancy in the immature tubers by exposing them to a lower temperature (17 C) in the dark. The development of dormancy was suppressed by 2,4-dinitrophenol, p-nitrophenol, and sodium azide.There are two stages of bud dormancy in the aerial tubers of Begonia evansiana, as in the case of dormant buds in many woody plants (5). One occurs in the immature tubers which require blue or far red light for their sprouting, and is called the photo-sprouting stage; the other appears in the mature tubers which require chilling for their sprouting, and is called the thermo-sprouting stage. These two states of dormancy correspond to those of the summer and the winter dormancy in woody plants, respectively. If the isolated immature tubers are exposed to red light or moderately low temperatures, however, they advance to the thermo-sprouting state (7). Dormancy-inducing effects of these treatments are negated by the application of inhibitors of biosyntheses of nucleic acids and proteins, which suggests that the DNA-RNA-mediated biosynthesis of proteins is an important event in the development of dormancy in the Begonia tuber (8). On the other hand, some workers have recently reported that some respiratory inhibitors as well as the inhibitors of nucleic acid and protein biosyntheses stimulate seed germination (2, 3, 9). These findings seem to indicate the participation of active synthetic systems in maintaining the dormant state in buds and seeds.It is well known that O2 is required for breaking dormancy of buds and seeds by chilling or stratification (10). However, little notice has been taken of the need of 02 for dormancy induction in both buds and seeds, although an anaerobic environment is reported to impose a secondary dormancy upon some kinds of seeds (1). The present work was undertaken to investigate the relation of 02 to bud dormancy in Begonia tubers. MATERIALS AND METHODSImmature and mature aerial tubers of B. evansiana Andr. were used as materials. The immature tubers at stages 4 to 6 as defined by the size of tubers (4) were isolated from the plants growing under short days in the field or greenhouse. The mature tubers, which were in a half-dormant state by receiving natural chilling in the field, were harvested late in N...

Spatio-temporal relief from hypoxia and production of reactive oxygen species during bud burst in grapevine (Vitis vinifera)

“…The transition to bud burst can be accelerated by numerous sub-lethal stresses, including transient inhibition of respiration, heat shock or hypoxia ( Esashi and Nagao, 1973 ; Erez et al ., 1980 ; Erez, 1987 ), as is also the case with seed germination ( Roberts, 1962 ; Siegel et al ., 1962 , 1964 ; Chen, 1970 ; Al-Ani et al ., 1985 ). ROS are proposed to be key signalling agents induced by respiratory inhibition, as they function both directly on the cell cycle and by modulating activities of plant growth regulators such as ethylene, abscisic acid and auxin ( Ophir et al ., 2009 ).…”