Keep reading both terms quite frequently while studying plant physiology. I did some research trying to establish their differences and I learnt that meristems are undifferentiated cells that can generate more cells that eventually could grow to form any part of the plant. But I really mess up both concepts, so I would really appreciate a comprehensive explanation of both of them separately. Thank you in advance for your help!
I looked in Taiz and Zeiger. Plant Physiology 5th ed and this is what I found:
Plant growth is concentrated in localized regions of cell division called meristems. Nearly all nuclear divisions (mitosis) and cell divisions (cytokinesis) occur in these meristematic regions. In a young plant, the most active meristems are called apical meristems; they are located at the tips of the stem and the root (see Figure 1.1). At the nodes, axillary buds contain the apical meristems for branch shoots.
The root and shoot apical meristems formed during embryogenesis are called primary meristems. After germination, the activity of these primary meristems generates the primary tissues and organs that constitute the primary plant body.
Most plants also develop a variety of secondary meristems during postembryonic development. Secondary meristems can have a structure similar to that of primary meristems, but some secondary meristems have a quite different structure. These include axillary meristems, inflorescence meristems, floral meristems, intercalary meristems, and lateral meristems.
Axillary buds are secondary meristems; if they are also vegetative meristems, they will have a structure and developmental potential similar to that of the apical meristem.
So, briefly, I could say that meristems are localized regions where undifferentiated cells reproduce themselves and originate new plant tissue. Axillary buds contain secondary (formed after embryogenesis) meristems. This meristem can behave like an apical meristem if it becomes vegetative i.e. either apical dominance disappears or it is excised and subcultured elsewhere.
A bud is capable of developing into a new individual while meristem can develop into any part of the individual. Buds can produce shoots, flowers, etc. while meristems have more variability - capable of developing into the tissues within the stem, a new individual, etc.
Meristems in plant's kingdom are functionally similar to stem cells in animal kingdom, even you can see it in their names, meriSTEMs & STEM cells ,stem cells are more flexible,okay going back to meristems ,buds are complex of apical or lateral meristems which are covered by special kind of leafs according to enzymatic change,photoperiod and climate conditions buds can produce new leafs,branches or reproductive parts such as flowers, so we can say that buds are some kind of meristems themselves,but there are some other kind of meristems which act more particular and they are referred as cambium which usually cause the production of cork and cause the lateral growth and vascular elements reproduction.