Botany - B.Ye. Yakubenko 2017

Part Three. Plant Kingdom (Planthae)
Chapter IX. Division Angiosperms, or Flowering Plants (Angiospermae, Magnoliophyta)
Laboratory Session Topic 14.47. Mint family (Lamiaceae). Figwort family (Scrophulariaceae)

General Remarks. The Lamiaceae family comprises about 200 genera and 3,500 species. They are distributed across all continents, with the greatest species diversity concentrated in the arid Regions of the Mediterranean.

This group includes herbaceous plants, subshrubs, and shrubs. The stem is quadrangular. Leaves are simple, exstipulate, and arranged oppositely. The stems and leaves bear glandular hairs or glandular scales that secrete Essential Oils. Flowers are zygomorphic, often bilabiate, and occasionally nearly actinomorphic (e.g., in species of the genus Mentha). The calyx is gamosepalous, bell-shaped, tubular, or bilabiate, typically 5-merous. The corolla is always 5-merous. Its lower part forms a tube, while the upper part forms a limb. Typically, the limb is bilabiate: the upper lip consists of two petals, and the lower lip consists of three. Rarely, the corolla is 4-merous or unilabiate, as seen in species of the genera Teucrium and Ajuga. Inside, the corolla tube is naked, smooth, or bears a ring of hairs slightly below the point of filament attachment, which restricts insect access to the nectar. The presence or absence of this adaptation is an important taxonomic feature. The androecium consists of four stamens attached to the corolla tube. Stamens attached closer to the lower lip are termed anterior or lateral, while those positioned further back are termed posterior or median. However, species of the genus Salvia and certain other genera possess only two stamens. The gynoecium always consists of two fused carpels. The Ovary is 4-lobed, with the style arising from its center. Flowers are aggregated into axillary dichasial cymes that form false whorls (verticillasters), as each whorl consists not of individual flowers, but of two oppositely positioned cymose inflorescences. These whorls are often grouped into complex racemose or paniculate inflorescences. The fruit is a set of four nutlets (tetranutlet).

The Scrophulariaceae family is represented by about 200 genera and 3,000 species distributed across temperate and warm regions of both hemispheres, with about 160 species found in the flora of Ukraine. Most species are herbs, and more rarely shrubs or trees (in the tropics). Leaves are alternate, opposite, or whorled, without stipules. Flowers are bisexual, zygomorphic, and less commonly nearly actinomorphic. The corolla is 4–5-lobed, bilabiate, rotate, or funnel-shaped; stamens are mostly 4, rarely 2 or 5; the pistil consists of two carpels with a superior bilocular ovary and numerous ovules. The fruit is a capsule, and rarely a berry.

In some genera (such as Pedicularis, Melampyrum, Euphrasia, and Odontites), There is a transition from autotrophic Nutrition to hemiparasitism or even complete parasitism (e.g., Lathraea). Representatives of many other genera (such as Scrophularia, Gratiola, Linaria, and Verbascum) occasionally infest meadows and pastures, reducing their productivity. Digitalis and certain Verbascum species are of significant medicinal importance. Antirrhinum, Calceolaria, Salpiglossis, and individual Veronica species are cultivated as ornamentals.

Objects: Lamiaceae family: white dead-nettle (Lamium album L.), ground-ivy (Glechoma hederacea L.), motherwort (Leonurus cardiaca L.), yellow archangel (Galeobdolon luteum Huds.), oregano (Origanum vulgare L.); Water mint (Mentha aquatica L.), gypsywort (Lycopus europaeus L.); Scrophulariaceae family: great mullein (Verbascum thapsus L.), common toadflax (Linaria vulgaris Mill.), figwort (Scrophularia nodosa L.), germander speedwell (Veronica chamaedrys L.), brooklime (Veronica beccabunga L.)

Tasks:

1. Perform a morphological Analysis of the main plant species from the specified families.

2. Study, describe, and illustrate the diagnostic taxonomic Features of the indicated species.

3. Identify the studied species, recording the identification steps using the dichotomous keys (leads and antileads).

4. Write out the floral formulas and draw diagrams of the identified plants.

Equipment and Materials: live, fixed, and herbarium specimens, stereomicroscopes, hand lenses, dissecting needles, tweezers, Glass slides, identification tables, and taxonomic keys.

Macroscopic Study of the white dead-nettle (Lamium album L.) The plant is a perennial herb, 30–140 cm tall. The ROOT System consists of adventitious roots formed on a horizontal rhizome. The stem is quadrangular, erect, sparsely branched, and hollow at the nodes. Leaf arrangement is opposite. Leaves are exstipulate; the lower ones are long-petiolate, while the upper ones are nearly sessile or short-petiolate; simple, ovate, softly pubescent above, nearly glabrous beneath, and rugose. The leaf margin is serrate. Flowers are gathered into spike-like inflorescences. Bracts are 6–8 times shorter than the calyx and Ciliate along the margin. The calyx is 1–1.5 cm long, consisting of five fused sepals that are subulate-pointed at the apex. Two of them are slightly larger than the others. The corolla is zygomorphic and bilabiate. The upper lip is helmet-shaped (galeate), and the lower lip is reflexed. Four stamens are concealed beneath the helmet of the upper lip; their anthers are arranged in pairs one below the other, and between them, an arcuate-curved style with a bilobed stigma is visible. There are 3–4 stamens: two median (posterior) ones are shorter and positioned beneath the lower lip, whereas two lateral (anterior) ones are longer than the median ones and attach to the lower lip. The lower part of the corolla tube features a hairy ring that blocks access to the Base of the tube. By tearing the calyx tube, one can observe a 4-lobed ovary. The lobes are obliquely truncate at the apex. The base of the ovary is surrounded by a lobed nectary disc. The fruit is a set of four nutlets. Floral formula: ↑K₍₅₎C₍₂₊₃₎A₍₂₊₂₎G₍₂₎. After the investigation, the plant is identified. Other species are studied and identified following the same Procedure.

Conclusion. During evolution, Lamiaceae and Scrophulariaceae developed as independent lineages. However, morphological comparison reveals that representatives of these families share certain features. Like the Lamiaceae, the Scrophulariaceae are represented by herbaceous plants (annuals and perennials), shrubs, and trees. The shoots of many representatives possess simple, exstipulate leaves that are arranged oppositely or in whorls.

Nevertheless, despite their external resemblance, Scrophulariaceae have no direct phylogenetic ties to Lamiaceae. Lamiaceae differ significantly from them in The Structure of the gynoecium and fruit. The gynoecium in Lamiaceae consists of two carpels, with a superior, 4-locular ovary containing a single ovule in each locule. In Scrophulariaceae, the ovary is superior, bilocular, and contains numerous ovules. The fruit is a set of four nutlets in Lamiaceae, whereas in Scrophulariaceae it is a capsule.

The formula for a typical flower in Lamiaceae is ↑K₍₅₎C₍₂₊₃₎A₂₊₂G₍₂₎, and in Scrophulariaceae it is ↑K₍₄₎C_(4,5)A_(4,5)G₍₂₎

Class="center">Self-Check Questions

1. What life forms represent the Lamiaceae and Scrophulariaceae families?

2. Which of the studied families is characterized exclusively by a quadrangular stem?

3. What type of phyllotaxy is typical for Representatives of the Scrophulariaceae family?

4. Which family includes plants whose stems and leaves are covered with glandular hairs or scales that secrete essential oil?

5. What is the shape of the corolla in members of the Lamiaceae family?

6. What are the differences in ovary structure between Scrophulariaceae and Lamiaceae?

7. What are the most important economic representatives of the Lamiaceae family?

8. What types of fruits are produced by members of the Scrophulariaceae family?

9. Name the most important medicinal and ornamental plants of the Scrophulariaceae family.

10. Write out typical floral formulas for representatives of the studied families.