Articles
OSMOTIC VERSUS NUTRITIONAL EFFECTS WHEN ROOTING ASPARAGUS MINICROWNS ON HIGH SUCROSE MEDIA
At lower sucrose levels, any roots that developed were usually long, fibrous, thin and weak, whereas at 60 g/l sucrose and above, storage roots developed.
Increasing sucrose levels also resulted in a substantial reduction in shoot growth.
The combination of high initiation frequency of storage roots and reduced shoot growth at 60 g/l sucrose provides ideal asparagus plantlets for transplantation into soil.
The increased root development observed at high sucrose levels could result from either nutritional or osmotic effects.
To discriminate between these options, we substituted the additional sucrose with equimolar levels of various non or poorly metabolised carbohydrates.
Supplements of mannose, sorbitol, cellobiose and maltose all promoted root initiation to a similar extent as sucrose.
Myo-inositol, melibiose and raffinose were less effective, whereas rhamnose, mannitol and lactose had no effect.
The roots initiated in response to these various alternative carbohydrates were short, thin and poorly developed.
We therefore conclude that osmotic effects provide an important trigger for root initiation, but it is the nutritional effects of high sucrose that stimulate the development of storage roots.