You could (if you really wanted to) call the propagules 'tiny cuttings'. Micropropagation involves a few cells of the 'mother plant', propagated in vitro, usually in sterile nutrient rich agar. This is tissue culture.

I would say that one considers it 'Tissue Culture' or Micropropagation if the tissue explant in question is reduced to an undifferentiated state from which the propagules are recovered by a redifferentiation. This is generally done by reversion of a bit of meristem tissue to a callus state which will grow as such and be divided, but can be carried to extremes as in growth from cultures of suspended single cells which has been done for tobacco and carrots among others.

George

Micropropagation is a subset of tissue culture. The process takes place in a sterile in vitro envirnment on a nutrient media that may or may not have a solidifying agent and typically contains a plant growth regulators to help differentiate shoot and or root differentiation.

There are two basic types of micropropagation, somalclonal and mericlonal. Somaclonal is considered to be far inferior to mericlonal MP in regards to commercial production. Somaclonal MP involves taking any plant tissue (leaf, stem, invitro germinated seedling, flower petal, fruit etc.) using PGR concentration and ratio to form an undifferintiated callus culture and then changin the PGR ratio and concentration to form shoots. And then rooting the shoots.

Mericlonal MP skips the callus phase and uses a plant meristem (terminal or axillary) to start an a shoot culture. The shoot culture is either proliferated or rooted.

Mericlonal is considered supperior becuase a callus phase can lead to somalclonal mutations. Which is a bad thing if you are propagating a cultivar and fidelity is important.

Many decades ago in a university lab we did what geoforce described as "the tissue explant in question is reduced to an undifferentiated state from which the propagules are recovered by a redifferentiation. That lab was called "in vitro propagation" or sometimes "tissue culture". Am I correct in assuming that "micropropagation" is more recent jargon?