4.
In Vitro Meristem and shoot-tip culture
4.1.
Explant terminology
The scientist who have attempted to recover pathogen-free plants through tissue culture techniques have indiscriminately designated the explants required to initiate cultures as ‘shoot-tip', ‘tip-meristem' and ‘meristem-tip'. The apical meristem of a shoot is the portion lying distal to the youngest leaf primordium, it measures up to about 100µm in diameter and 250µm in length. The apical meristem together with one to three young leaf primordia, measuring 100-500µm, constitutes the shoot-apex (Figure 7.2A and B). Although the chances of eradicating viruses is higher through ‘meristem' culture, in most successful reports virus-free plants have been raised by culturing 100-1000µm long explants which could be according to the above definition is referred as ‘shoot-tip'. To distinguish it from the in vivo technique of propagation through shoot-tip cuttings, the term ‘meristem-tip' culture has been preferred for in vitro culture of small shoot-tips.
