Botany - B.E. Yakubenko 2017

Part Three. Kingdom Plantae
Chapter IX. Division Angiosperms, or Flowering Plants (Angiospermae, Magnoliophyta)
Laboratory Class Topic 14.52. Hornwort family (Ceratophyllaceae)

General Remarks. Water/188.html">The Hornwort family (Ceratophyllaceae) comprises perennial, aquatic, rootless herbaceous plants. The leaves are whorled, dichotomously forked, with thread-like or linear, spiny-toothed segments. Flowers are solitary in the leaf axils, unisexual, with a simple 12-parted perianth in staminate flowers and an 8-12-parted perianth in pistillate ones. Stamens number 12–16. There is a single pistil with a superior unilocular Ovary and an awl-shaped style. The plants are monoecious. The fruit is a nutlet, tipped with the persistent remnant of the style forming a spine, often accompanied by additional lateral spines.

When examining representatives of this family, attention should be paid to leaf structural features, which may be rigid, dichotomously once- or twice-forked, dichotomously three- to four-forked into 8–15 thread-like segments, or dichotomously three- to four-forked into thread-like, distantly spiny-toothed segments. Flowers are actinomorphic, unisexual, with a simple 8–12-parted perianth in pistillate flowers and a 12-parted perianth in staminate ones. Important diagnostic features include fruit shape, the size of its apical spine, and the Morphology of the fruit margin.

Objects:

1. Coontail / Rigid hornwort (Ceratophyllum demersum L.)

2. Don hornwort (Ceratophyllum tanaiticum Sapieg.)

3. Submerged hornwort (Ceratophyllum submersum L.)

Tasks:

1. Familiarize yourself with The Diversity of plants in the hornwort family, perform a written morphological analysis, and identify the plants.

2. Perform the morphological analysis and identification using the coontail (Ceratophyllum demersum) as an example.

3. Study the botanical CHARACTERISTICS OF THE Ceratophyllaceae family.

Equipment and Materials: hand lenses, dissecting needles, taxonomic keys, herbarium and live specimens, laboratory notebook.

Macroscopic Studies of the Coontail (Ceratophyllum demersum L.) Begin your examination of the plants by analyzing their morphological Structure According to the outline provided in this laboratory practical. Ceratophyllum demersum is a perennial, herbaceous plant entirely submerged in water. Roots are absent. Stems are slender, brittle, 20–100 cm long, with occasional axillary branches. Leaves are simple, whorled, rigid, dichotomously once- or twice-forked, 1.5–2.0 cm long. Flowers are solitary, regular, unisexual, located underwater in the leaf axils. The plants are monoecious. The perianth is simple. Staminate flowers are 12-parted, arranged in rosette-like clusters in the leaf axils, and contain 12–16 stamens. Pistillate flowers are solitary in the leaf axils, with an 8–12-parted perianth. There is a single pistil with a superior unilocular ovary and an awl-shaped style. The fruit is a dry, indehiscent, single-seeded nutlet. Floral formula: *Ca_оCo₁₂A_12—16G₀; *Ca₀Co_8—12A₀G₁.

Key steps for family identification: 1, 9—, 15, 16, 17—, 19—, 20—, 21—, 22, 23—, 24—, 25—, 26, Ceratophyllaceae — Ceratophyllaceae.

Key steps for genus and species identification: 1. Coontail — Ceratophyllum demersum L.

Conclusion. Ceratophyllaceae are aquatic, perennial, rootless plants with whorled, dichotomously forked leaves. The flowers are unisexual, with a simple, reduced perianth adapted to hydrophily. Vegetative Reproduction predominates over seed reproduction.

Class="center">Review Questions

1. Why are members of the Ceratophyllaceae classified as perennial plants?

2. Do Representatives of the hornwort family possess roots?

3. What type of leaves is characteristic of hornworts?

4. What is the sexual type of flowers typical for hornworts?

5. How many segments make up the perianth in hornwort flowers?

6. How many stamens are contained in a hornwort flower?

7. What type of gynoecium is characteristic of hornwort flowers?

8. Name the representatives of the Ceratophyllaceae family and state their practical significance.