Lamium multifidum

Atasagun, Bayram, Aksoy, Ahmet & Martin, Esra, 2015, Contribution to the systematic knowledge of Lamium multifidum and L. orientale (Lamiaceae), Phytotaxa 203 (2), pp. 147-158 : 149-150

Lamium multifidum

Root:—As a protective tissue, the periderm is located in the outermost layer. Under the periderm is a parenchymatous cortex consisting of 6–7 layers of cells. The endodermis layer cannot be distinguished. Underneath the cortex layer is the vascular cylinder, consisting of the xylem and phloem. The phloem cells are smaller and less numerous, while xylem cells cover a larger area. A cambium consisting of 2–3 layers of cells can be distinguished immediately under the phloem. Within the xylem tissue under the cambium, the trachea and the tracheids can be identified. The pith region contains parenchymatous cells, which have rounded shapes ( Fig. 3A ).

Stem:—The stem is quadrangular. The outermost layer is covered with the epidermis, which consists of a single layer of rectangular cells. Localized patches of trichomes are also observed on the epidermis. There is an 8–9 cell thick collenchyma layer immediately under the epidermis on the corners of the stem. A cortex consisting of 2–3 layers of oval parenchymatous cells is located under the collenchyma in the corners; the same cortex consists of 5–6 layers of cells underneath the epidermis in other areas. The vascular bundles at the corners are larger than those located between the corners. The trachea and tracheids within the vascular bundles are distinct and pronounced. The phloem cells are smaller and less numerous, mostly being localized on the xylem. There is a 1–2 layer cambium between the phloem and xylem. On the lower side of the vascular bundles is the pith region, which consists of parenchymatous cells and covers a large area ( Fig. 3B ).

Leaf:—In the cross section of the leaf, it is possible to observe a single layer of regular and rectangular epidermal cells on both the upper and lower sides. The lower epidermal cells are smaller than the upper epidermal cells. Hairs are common on both the upper and lower epidermises. There is a mesophyll layer between the two epidermises. The leaf type is bifacial (dorsiventral). Under the upper epidermis is a palisade parenchyma consisting of regularly arranged cells with very little space between them. Under this palisade parenchyma is a spongy parenchyma consisting of irregularly arranged cells with numerous spaces between them ( Fig. 3C ). In the center of the median vein, which is quite pronounced and located centrally on the leaf, there is a vascular bundle consisting of the xylem and phloem. The vascular bundles are surrounded by a single layer of sclerenchymatic cells. The region between the sclerenchymatic cells and the epidermis is occupied with parenchymatous cells ( Fig. 3D ).

Figures

FIGURE 3. Cross section of Lamium multifidum A. Root. B. Stem. C–D. Leaf (p: periderm, c:cortex, ca: cambium, x: xylem, t: trachea, pi; pith, pr: pith ray, co: collenchyma, ph: phloem, ad: adaxial surface, ab: abaxial surface, ue: upper epidermis, le: lower epidermis, p: parenchyma, pp: palisade parenchyma, sp: spongy parenchyma, vb: vascular bundle, h: hair).