Lycophyta-3

*As we have seen, there are several types of stems produced by Lycopodium. These include an underground Rhizome, a horizontal Stolon and Aerial Stems. Diagram of a Lycopodium* Plant The Apical Meristem is multicellular. This distinguishes it from the other plants we have seen so far. Multicellularity is a feature of the most advanced plants and probably represents a significant adaptation. However, it is unclear how this might be advantageous. Presumably the multicellular apex may have greater flexibility in terms of leaf initiation & possibly in terms of internal tissue differentiation. Lycopodium Shoot Apical Meristem (SAM) with Leaf Primordia. Leaves are initiated from single cells or a small group of cells, close to the Shoot Apical Meristem (SAM). This is typical for most vascular plants. The Epidermis of the stem typically has Stomata. The outer Cortex usually contains Chlorenchyma. This photosynthetic tissue may contain a lot of air spaces & can be continuous with the leaves. The take home message is that the stems can make a major contribution to the total amount of photosynthesis that takes place in Lycopodium. Microphylls represent a significant advance compared to leaves of the Bryophyta. However, the plant may still need a strong contribution from its stem in order to survive & thrive. Some of the internal cortical cells have thick walls which become lignified. These constitute Sclerenchyma tissue which imparts strength to the stem. Sclerenchyma cell walls typically contain Lignin and stain red with Phloroglucinol. Leaf traces are present.
Stem X-section stained with Phloroglucinol	Stem X-section stained with Toluidine Blue
An Endodermis is visible in young stems but may be hard to find in mature stems.
Lycopodium Rhizome X-section - Note the Sclerenchyma fibers which have stained red. The Xylem in the Stele has also stained red. The red color indicates the presence of Lignin.