Chapter 4-Fruits and Nuts of Temperate Regions What is a fruit? A fruit is botanically defined as a mature, or ripened ovary of a flower along with its contents and any adhering accessory structures. Seed and fruit maturation can occur without fertilization. agamospermy (without sperm) parthenocarpic (“virgin fruit”) Ex: Navel oranges – vegetatively propagating parthenocarpic mutants Ex: Seedless grapes- hormones that trigger fruit production without fertilization Table 4.1 Fruit Types with examples

Untreated Treated with

gibberellins

Figure

29.17

Fruits are often classified by: The ovary can be simple or compound. The notion of simple or compound ovaries involves the concept of the carpel. Foliar Hypothesis The ovary was derived from a leaf-like structure with uncovered ovules. During the course of plant evolution, this flat structure unfolded and produced the closed characteristics of angiosperms. A simple ovary is derived from one carpel, a “single, folded, leaf-like unit.” A compound ovary is produced by the fusion of two or more of these leafy structures.

Simple fruits are derived a flower with a single ovary (simple or compound). The nature of a simple fruit depends on whether the ovary is superior or inferior. A superior ovary An inferior ovary If a fruit results from a single, superior ovary, it will have one or more seeds surrounded by the pericarp. The pericarp is made up of 3 layers of ovary wall:

The pericarp can develop in various ways and lead to an assortment of fruit types. Dry fruits are described as: Fruits may be dehiscent (splits open) Peas are dehiscent, the pods split along the side releasing the seeds. Additional simple, dehiscent fruits: Follicle The follicle develops from a single carpel and opens along only 1 side. Capsules are simple fruits derived from compound ovaries

Simple fruits can also be indehiscent (doesn’t split open), and either dry or fleshy. Nuts are one type of dry, indehiscent fruit. Other dry, indehiscent simple fruits include: achene The sunflower “seed” is actually an achene; the shell is the pericarp. caryopsis The “seeds” of corn and other grasses. samara The winged fruits of maples and elms. schizocarp The fruit of the carrot family that splits into two halves at maturity.

Fleshy fruits are often given different names depending on which part becomes the juicy, edible portion. Fleshy, simple fruits include: Berry Berries are derived from a superior ovary (compound), and many seeds are embedded in the fleshy pericarp. Drupes are berry-like fruits with the seed enclosed in a hard stony endocarp. A hesperidium is another specialized berry and includes the citrus fruits. The thick peel that has numerous oil cavities is the exocarp and mesocarp.

Because the pericarps of inferior ovaries are fused with the bases of floral parts surrounding them, the fruit wall consists of the ovary wall and extra, or accessory (non-ovary) parts. Many plant families have distinct accessory fruits. The fruits of the squash family are called pepos, distinguished by their hard rind. If numerous superior ovaries are borne within a single flower, then each ovary matures to form part of a compound fruit known as an aggregate fruit. Multiple fruits are the enlarged ovaries of multiple flowers that more or less fuse together.

Stamen

Stigma Ovary

Raspberry flower

Aggregate fruit

Stamen

Carpels

Carpel (fruitlet)

Raspberry fruit

Pineapple inflorescence

Multiple fruit

Flower

Each

segment

develops

from the

carpel

of one

flower

Pineapple fruit

The rose family (Rosaceae) produces the majority of our familiar dessert fruits. The structure of the fruit varies across genera. Malus (apple) and Pyrus (pear), as well as Cydonia (quince) produce pomes. Apples are the most important temperate fruit tree crop. (60% of the world’s temperate fruit tree production) The modern apple (Malus domestica = Malus pumila) is a direct descendant of Malus sieverii, a wild species that grows in southeastern Kazakhstan. The earliest evidence of domesticated apples dates to 3000-4000 years ago from the Middle East region. The earliest record of grafting was 300 B.C. Cultivated edible apples were brought to North America by Europeans. Apples were first planted in North America in the 1620’s on Bunker Hill.

Pears are the second largest temperate fruit tree crop worldwide. The genus Pyrus originated in Asia and the widely cultivated species is Pyrus communis. The slightly gritty texture of pears is caused by the presence of sclereids or stone cells. In Asia, Pyrus pyrifolia (Asian pear), are important commercial species commonly sold in U.S. supermarkets. The third economically important fruit of the apple group is the quince (Cydonia oblonga).

The genus Prunus gives us several important fruits including: The fleshy mesocarp is the part eaten in all the fruits of the plum group The ancient origin of the genus is central or western China. In Eurasia, plums, peaches and apricots have been cultivated for more than 2000 years. All cultivated cherries are derived from Old World species. In 1847, the Lewelling brothers settled in Oregon with several hundred cherry seedlings. Maraschino cherries are named after an Italian cordial, maraschino (after the marasca cherrry). Peaches, Prunus persica, are the third most important tree fruit crop in the United States.

Peaches are native to China and have been cultivated for thousands of years. The peach tree has come to symbolize long life and wisdom. Spaniards introduced peaches to Mexico in the late 1500’s. The cultivation of peaches has spread with many varieties that allow their growth in a variety of climates.