Botany - B.Ye. Yakubenko 2017

Part Three. The Plant Kingdom (Plantae)
Chapter IX. Division Angiosperms, or Flowering Plants (Angiospermae, Magnoliophyta)
Laboratory Class Topic 14.48. Cabbage Family (Brassicaceae). Aster Family (Asteraceae)

General Remarks. The Brassicaceae family comprises 376–380 genera and about 3,200 species distributed almost globally, particularly in regions with dry temperate climates. Their highest concentration is found in the Mediterranean, South Africa, and Western and Central Asia; in Ukraine, there are over 200 species.

The Brassicaceae family includes annual, biennial, and perennial herbs, and occasionally subshrubs. In some plants, the roots are modified into ROOT crops. Phyllotaxis is alternate, with basal leaves forming a rosette. The inflorescence is predominantly a raceme. Flowers are actinomorphic, bisexual, and feature nectaries. The perianth is double. The calyx consists of four free sepals. The corolla is tetramerous, with petals arranged in a cross-like (cruciform) pattern. There are six stamens: two outer ones are shorter, and four inner ones are longer. The pistil consists of two fused carpels. The Ovary is superior, falsely bilocular due to The Development of a false septum. The fruit is a multi-seeded silique, silicle, or nutlet. The seeds are rich in fatty oil and often in Glycosides. Brassicaceae are highly polymorphic and include a significant number of cultivated species and weeds. The formula of a typical flower is *K₄C₄A₂₊₄G₍₂₎

The family Asteraceae is one of the largest families of angiosperms. The number of species is estimated to range from 18,000–20,000 to 25,000. They are distributed globally, although they rarely form continuous plant cover over large areas. The ecological range of the family is remarkably broad—from humid, hot tropics to the arid deserts of Asia and Africa, and the cold Regions of the Arctic and Antarctic. Asteraceae are mostly herbs or tropical subshrubs, as well as shrubs, lianas, or even small trees. Leaves are alternate, less frequently opposite, exstipulate, and variable in shape, size, and degree of dissection. Flowers are small, gathered on a common disc-shaped receptacle; the inflorescence is a capitulum (HEAD). Flowers are pentamerous and arranged in four whorls; all flowers in the head may be identical, or the outer ones may differ from the inner ones. The calyx is either entirely reduced or transformed into hairs, bristles, or membranous outgrowths that persist in the fruit. The corolla is sympetalous, actinomorphic (tubular or funnel-shaped), or zygomorphic (bilabiate, unilabiate, or, most commonly, ligulate). There are five stamens with filaments attached to the corolla tube. The ovary is inferior, composed of two carpels, unilocular, with a single ovule. The fruit is an achene, often equipped with a pappus or a membranous crown.

Depending on The Structure of the corolla, four MAIN TYPES OF Asteraceae flowers are distinguished: 1) tubular flowers—bisexual, actinomorphic, with a tubular, five-lobed corolla; 2) false-ligulate (ray) flowers—pistillate only, often acting as marginal flowers in the capitulum; due to the reduction of the upper lip, these flowers have become unilabiate, with their lower lip ending in three Teeth; 3) ligulate flowers—bisexual, zygomorphic, with the corolla ligule ending in five teeth; 4) funnel-shaped flowers—sterile marginal flowers, zygomorphic, with the corolla having five unequal teeth, giving it a bilabiate appearance.

Objects. Living, fixed, or dried plants. Brassicaceae family: garlic mustard (Alliaria petiolata (Bieb.), Cavara et Grande), shepherd's purse (Сapsella bursa-раstoris (L.) Medik), field pennycress (Thlaspi arvense L.), wild radish (Rарhanus raphanistrum L.), cabbage (Brassica oleracea L.), great yellow-cress (Rorippa amphibia (L.) Besser), cuckoo flower (Cardamine pratensis L.); Asteraceae family: Canadian fleabane (Еrіgerom саnаdensis L.), gallant soldier (Galinsonga parviflora Cav.), milfoil (Асhillea submillofolium L.), dandelion (Taraxacum officinale Webb ex Wigg.), cornflower (Сеntаurea cyanus L.); perennial sow thistle (Sоnсhus аrvensis L.); hemp-agrimony (Eupatorium cannabinum L.); nodding bur-marigold (Bidens cernua L.)

Tasks:

1. Perform a morphological Analysis of the main plant species from the Brassicaceae and Asteraceae families.

2. Examine, describe, and sketch the characteristic systematic Features of the specified species.

3. Identify the studied species.

4. Write down the formulas and draw diagrams of the identified species.

Equipment and Materials: binocular microscopes, magnifiers, dissecting needles, tweezers, Glass slides, identification tables, and botanical keys.

Macroscopic Study of the perennial sow thistle. A perennial herbaceous plant, 60–150 cm tall. The underground part features a rhizome with adventitious buds and roots. The stem branches only in the upper part; it is erect and round in cross-section. Leaves are alternate, simple, sessile, and pinnatifid, with the lower ones petiolate. Stipules are absent. Capitula are many-flowered, gathered in a panicle. Flowers are zygomorphic, with four whorls. The calyx is modified into a pappus (tuft of hairs). The corolla is ligulate and yellow. The androecium consists of five stamens forming a tube. The gynoecium is paracarpous, formed by two carpels. The ovary is inferior. The fruit is an achene.

Macroscopic study of garlic mustard. Garlic mustard is a biennial plant, 25–60 (100) cm tall. The Root System is taproot-based, with a prominent main root that stands out in thickness and length, accompanied by shorter and thinner lateral roots. When the root is rubbed, a distinct garlic odor is released, hence the common name garlic mustard.

Carefully examine the stem: its outline is round. In cross-section, it is filled with ground and Vascular Tissues. Simple hairs are scattered all over the stem, and it is hairy-pubescent at the base. Phyllotaxis is alternate. Note that the leaves are heterogeneous: lower leaves are long-petiolate, reniform, with a purplish or bluish hue; middle leaves are short-petiolate and cordate; upper leaves are sessile, ovate-cordate or triangular, and sharply dentate. The inflorescence is a raceme. Flowers are attached to the axis by elongated pedicels. A characteristic feature of Brassicaceae is structural constancy in their flowers. Note that garlic mustard clearly displays four greenish, free sepals arranged crosswise. There are four white petals arranged cross-wise (in a cross), which is why the family was formerly known as Cruciferae (crucifers); today, the preferred name is Brassicaceae. Surrounding the double perianth (calyx and corolla) is a two-whorled androecium. The inner whorl consists of four longer stamens, and the outer whorl consists of two shorter stamens. The gynoecium consists of two carpels that form a bilocular syncarpous ovary. The style is short and thickened. The stigma is entire and capitate.

The flower formula is as follows: *K₄C₄A₄₊₂G₂.

Closely examine the STRUCTURE OF THE fruit. Its length is many times greater than its width, which is why it is called a silique. A longitudinal partition runs down the middle, to which numerous small dark or dark-brown seeds are attached. The Valves are convex, with a prominent midvein and two thin, inconspicuous lateral Veins.

Following the examination, identify the plant using the methodology described above. Study and identify other species using the same scheme.

Conclusion. The Brassicaceae family is quite polymorphic. The genera are so closely related that clear and reliable morphological differences between them are frequently absent. The greatest uniformity is observed in flower structure. Some variations do occur in fruit structure. Representatives of the Brassicaceae family may produce the following types of fruits: 1) a linear, dehiscent silique; 2) an indehiscent, articulated silique; 3) a silicle or nutlet.

Compared to Brassicaceae, the Asteraceae family is an evolutionarily higher and more numerous group of plants. Many genera within this family are extremely polymorphic because they are undergoing active speciation (form generation). They are characterized by high ecological plasticity and high reproductive energy, both through seeds and vegetatively. Representatives of Asteraceae are very frequently a component of plant cover and rank among the leading families in the flora of Ukraine.

Class="center">Self-Control Questions

1. Name the taxonomic characteristics and life forms represented by the Brassicaceae and Asteraceae families.

2. Representatives of which studied family exhibit uniform flower structure?

3. Describe the characteristic features and write the flower formula for representatives of the Brassicaceae family.

4. What types of flowers are found in representatives of the Asteraceae family?

5. Which flower types in representatives of the Asteraceae family are sterile?

6. Which of the bisexual flowers in the Asteraceae family are zygomorphic?

7. Name and describe the Structural Features of the inflorescences of the studied families.

8. What types of fruits are found in representatives of the Brassicaceae family, and What are the structural differences between them?

9. Name the most important economically significant representatives of the Brassicaceae family.

10. Name the most important economically significant representatives of the Asteraceae family.