Abstract
As previously reported, both MH-induced swelling and long-day-induced bulbing were caused by inhibition of meristematic activity in the buds of onion plants. On the basis of these results, this investigation was undertaken to clarify the relationship between the bulbing or swelling and function of meristematic region of the onion using cultivar‘Kaizuka-wase’, and this paper reported that the swelling of sheath was induced by means of mechanical procedure or removal of meristematic region.
1. Each leaf of onion plants grown under short-day was removed separately from the disc, and was implanted in sterilized sand after curing. Intact plants served as control were kept under the same condition as they were implanted.
Twenty days after implanting, the basal leaf- sheaths of the treated plants swelled even in short-day condition, but those of intact plants did not swell.
Especially, the 3rd and the 4th leaf-sheath of the treated plants swelled three or four times as thick as the same sheaths of the intact plants, but the inner sheaths less swelled.
Both parenchyma cells and inter-cellar spaces of the sheaths of the treated ones enlarged in size, although it was not followed by an increase in sugar content in the leaf-sheath.
2. The leaf-sheaths failed to swell when leaves removed about two-third of blade were implanted under short-day and even when complete leaves were implanted under dark condition.
On the basis of this result, it seemed reasonable to assume that cell enlargement will depend on the photosynthesis or on the process of high intensity of light.
3. The onion plants removed apical buds from the lower part of disc (bottom) by means of razer blade were planted in sterilized sand under short-day, and the plants with apical bud served as control.
Thirty days after treatment, the leaf-sheaths of the treated plants swelled as thick as those of ‘leaf-culture’. On the contrary, the onion plants with apical bud failed to swell their sheaths.
4. Both onion plants removed apical bud and intact plants were grown under short-and long-day conditions.
The plants without apical bud swelled their sheaths either in long-day or in short-day, but failed to elongate their leaves, and plants with apical buds swelled only in long-day. Long-day condition was more effective in swelling than short-day condition.
