Botany - B.Ye. Yakubenko 2017

Part Three. Kingdom Plantae
Chapter IX. Division Angiosperms, or Flowering Plants (Angiospermae, Magnoliophyta)
Laboratory Session Topic 14.42. Structure and Types of Fruits. Infructescences

General Remarks. The fruit is designed to protect and disperse seeds and is characteristic of angiosperms only. It develops from a flower As a result of its transformation following double Fertilization. The gynoecium plays the primary role in fruit formation. In some cases, other floral elements also participate in this process: the receptacle, and the bases of the stamens, petals, and sepals. In certain varieties (such as grapes and cucumbers), fruits form without fertilization and do not produce seeds. Such fruits are called parthenocarpic.

A fruit consists of the pericarp and the seed. The pericarp develops from the Ovary wall and sometimes from other PARTS OF THE flower; it comprises three layers: the exocarp (outer layer), the mesocarp (middle layer), and the endocarp (inner layer).

The Diversity of fruits is extremely wide, driven by their adaptation to seed dispersal. A fruit is called simple if it develops from a single pistil (e.g., in peas).

Simple fruits may break apart into separate segments (such as in caraway, maple, and carrot). Therefore, they are called schizocarpic. If simple fruits break along transverse partitions into single-seeded segments, they are called loments (e.g., wild radish).

A fruit formed by several pistils of a single flower (like raspberry or buttercup) is called an aggregate fruit. Unlike true fruits, multiple fruits (or infructescences) develop from an entire inflorescence (such as in mulberry, fig, and pineapple). In The formation of multiple fruits, both the flowers and the inflorescence axis are involved. The further Classification of simple and aggregate fruits is based on the following features: the consistency of the pericarp (dry or fleshy), the number of seeds (one or many), the mode of pericarp dehiscence (dehiscent or indehiscent), and the number of carpels forming the fruit, among others.

Objects: Fruits of various types and plant species.

Tasks.

1. Study the Structural Features of fleshy fruits.

2. Study the structural features of simple fruit types.

3. Study the structural features of various types of aggregate fruits and multiple fruits.

Equipment and Materials: Hand lenses, scalpels, dissecting needles, live and preserved material, charts, slides, anatomical models, etc.

Macroscopic study of fleshy fruits. Using a plum or cherry fruit as an example, examine The Structure of fleshy fruits. It is advisable to make a longitudinal section through the pulp. The following constituent parts can be distinguished on a Cytology/practical/54.html">Longitudinal section of the fruit: the exocarp, which is a thin outer Skin often covered with a waxy bloom or film; the mesocarp, which constitutes the main bulk of the pericarp and serves as a storage tissue for nutrients; the endocarp, the inner layer of the pericarp that forms a stony layer in stone fruits; and the seed, which ensures plant propagation. Make a drawing of the longitudinal section of the fleshy fruit and label its constituent parts.

Macroscopic study of a raspberry fruit. Take a raspberry fruit and make a longitudinal section through it. This section (Fig. 110) reveals an elongated, conical receptacle to which simple drupelets are attached. In each drupelet, one can distinguish the exocarp, mesocarp, and endocarp, which were already observed in the cherry drupe. Therefore, such a fruit, where simple fruitlets develop on a common receptacle, is called an aggregate fruit.

Using a tomato fruit as an example, examine the structure of a berry (see Fig. 110). Here, the exocarp, mesocarp, locules (seed chambers), central axis (or Placenta), and seeds can be clearly distinguished.

Using a strawberry fruit as an example, study the STRUCTURE OF THE accessory aggregate fruit, specifically an aggregate achene (see Fig. 110). To do this, make a longitudinal section of the fruit and carefully examine its structure. You will observe a greatly enlarged, fleshy receptacle and numerous achenes embedded in the fruit pulp.

The raspberry fruit is similar to a berry but differs from it in having a leathery exocarp, a fleshy mesocarp, and a woody endocarp. The fleshy part is formed by enlarged placentae.

Macroscopic study of dry fruits. Dry fruits are those in which the hygroscopic moisture content does not exceed 15%. They include simple, aggregate, and schizocarpic fruits. Draw the most common types of dry Water/157.html">Fruits and Their constituent parts (see Fig. 110).

A legume (pod) is a simple dehiscent fruit formed by two Valves, to the margins of which endosperm-free seeds are attached. The fruit is formed from a single carpel but dehisces along two sutures—a true and a false one.

A silique is formed by two carpels, has two locules, and features a transverse partition to which the seeds are attached. A silicle has a similar structure, but its width is equal to its length, or its width is ²/₃ of its length.

A capsule is formed by 3–5 or many carpels. Through the fusion of their margins, a 1-, 2-, or multilocular capsule is formed. Examine the capsule of a poppy, datura, or henbane.

A caryopsis is a single-seeded fruit in which the seed coat is fused with the pericarp. You observed the longitudinal section of a caryopsis in wheat when studying nutrient reserves.

A nut is a single-seeded fruit in which the pericarp is stony and not fused with the seed, as seen in hazelnuts.

An achene is a single-seeded indehiscent fruit in which the pericarp is leathery and not fused with the seed. An example is the achene of a sunflower.

A samara is a single- or two-seeded fruit in which the seed is enclosed by unfused leathery or woody pericarp walls bearing a wing-like appendage, characteristic of the fruits of ash and maple.

A follicle is a dehiscent fruit formed by a single carpel. The seeds are attached to the margin of the leathery valve, as seen in the fruit of larkspur (Delphinium).

Class="center">Figure 110. STRUCTURE AND TYPES of fruits:

a — nut; b — achene; c — aggregate achene of strawberry; d — legume; e — silique;

e — silicle; f — follicle; g — samara; h — double samara; i — drupe;

j — cross-section of a drupe; k — aggregate drupe; l — valvate capsule; m — poricidal capsule; n — denticidal capsule; o — acorn; p — caryopsis; q — berry; r — cross-section of a berry; 1 — valves; 2 — seeds; 3 — exocarp; 4 — mesocarp; 5 — endocarp; 6 — seed; 7 — central partition; 8 — cupule; 9 — fruit; 10 — pericarp;

11 — seed coat; 12 — endosperm; 13 — embryo; 14 — locules of the fruit;

15 — seeds; 16 — free central placenta