BOTANY WITH THE BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

VIII. BASICS OF PLANT MORPHOLOGY AND ANATOMY

Features of Reproduction in Angiosperms

Morphology of Inflorescences. Types of Inflorescences

An inflorescence is one of the key adaptations for plant pollination. Flowers can be solitary or gathered into inflorescences. An inflorescence is defined as a group of flowers borne on a common axis devoid of true foliage leaves. There are two main groups of inflorescences: indeterminate and determinate.

Indeterminate, or racemose, inflorescences are characterized by unlimited apical growth and monopodial branching, which results in The production of an indefinitely large number of flowers. The first flowers are laid down from the base upwards, and fruits and seeds ripen in the same manner. Indeterminate (racemose, monopodial) inflorescences are divided into simple and complex.

Simple indeterminate inflorescences are those that feature a single, unbranched common axis with flowers positioned along it (Fig. 86). Among them, the following types are distinguished.

A raceme is an inflorescence in which flowers on pedicels are arranged along the main axis of the first order (bird cherry, shepherd's purse, acacia).

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Fig. 84. Types of inflorescences:

A - simple indeterminate (racemose): 1 - raceme, 2 - simple spike, 3 - spadix,

4 - simple umbel, 5 - HEAD, 6 - capitulum (head), 7 - corymb; B - complex indeterminate (racemose): 8 - compound spike,

9 - panicle, 10 - compound umbel; C - determinate (cymose): 11 - cyme (rhipidium/bostryx), 12 - bostryx, 13 - dichasium, 14 - pleiochasium.

A simple spike is an inflorescence in which sessile flowers develop on the first-order axis from the base upwards (plantain).

A spadix is an inflorescence in which sessile flowers develop sequentially from the base upwards on a thickened axis (corn, calla lily, sweet flag).

A corymb is an inflorescence in which the flowers lie in almost the same plane, but their pedicels attach at varying heights along the first-order axis (pear, plum, sweet cherry, apple).

An umbel is an inflorescence in which flowers on pedicels arise from a single apical node of the first-order axis and are typically located at the same level (onion, primrose).

A head (capitulum) is an inflorescence in which flowers with short pedicels are densely arranged on a shortened, convex first-order axis (clover).

A capitulum (basket) is an inflorescence in which sessile flowers are arranged on a broadened, flat first-order axis (sunflower, oxeye daisy).

Complex indeterminate inflorescences are those in which axes of the first, second, third, and higher orders can be distinguished along a common axis. They comprise several different types.

A panicle is characterized by the fact that the axillary buds of the first-order axis develop not into solitary flowers, but into simple racemose inflorescences (oat, millet, bluegrass, fescue, reed) (Fig. 84).

A compound spike is distinguished by the fact that simple spikelets are located in the axils of small bracts along the first-order axis (wheat, rye, ryegrass).

A compound umbel is an inflorescence in which simple umbels, known as umbellets, are arranged on a shortened first-order axis. General involucres are situated at the Base of the primary rays, while involucels are present at the base of the secondary rays (carrot, dill, chervil, cow parsley).

Determinate, or cymose, inflorescences are characterized by sympodial or pseudodichotomous branching (Fig. 84).

A monochasium is an inflorescence in which the main axis terminates in a flower, and further growth continues through axes of the second and subsequent orders, which also end in The formation of new flowers. If the lateral axes diverge in the same direction, a bostryx (helicoid cyme) is formed (lungwort, bugloss, comfrey). When the lateral axes diverge alternately in different directions, a rhipidium (scorpioid cyme) is formed (gladiolus).

Dichasium is an inflorescence in which two opposite axes arise below the terminal flower, each ending in a flower and in turn producing two bracteate axes, repeating this branching pattern (e.g., Stellaria).

Pleiochasium is an inflorescence in which three or more bracteate axes arise below the main axis that ends in a flower, forming a whorl of monochasia or dichasial inflorescences (e.g., spurge).