Topic 27: Fruits I 

Fruits--What happens during the ripening of a fruit? 

 All fruits have essentially the same two phases of growth--

 Phase 1--development of the seeds, fruit parts; at this stage the fruits are hard, not attractive in color or flavor.  If eaten or picked at this stage the viable seed are not formed yet.

 Phase 2--involves ripening.  Seeds are essentially mature and all parts of the fruit are formed. Fruit now becomes attractive for animal. Changes color, taste, etc.  As part of ripening there is a great increase in metabolism, consumption of oxygen and production of CO2.

 The change from phase 1 to 2 is triggered by a hormone called ethylene, which is a gas, produced within the green fruit, and triggers ripening; if ethylene is removed by filters, and then ripening is prevented.  Another way of controlling ripening is to slow down metabolism.

 Commercial fruit growers and shippers control ripening by controlling ethylene, preventing the fruit from getting to the stage they make it, or filtering it out.

 Apples are stored in high nitrogen gas chambers, so oxygen is not available for metabolism.  Ethylene is filtered out of the air.  Tomatoes and bananas are picked green and dosed with ethylene prior to sale to cause them to ripen.  One bad apple will spoil the barrel--a saying that reflects the promotion of ripening.

 Why does a banana or a tomato, or a peach become soft?  The glue that holds the cells together gets broken down, and the cells become loosened from each other.

 Apples--Most important temperate fruit crop.  Are members of the rose family, with peaches, pears, cherries, strawberries, raspberries, almonds, plums, apricots.

 Apples originated in Eurasia and have been eaten since prehistoric times.  The modern apple was derived from the crabapple, which is defined as an apple that is smaller than two inches across.  Selection was practiced early, so the Romans had 22 different varieties.  By the 1800s there was a great proliferation of varieties, many of which have been lost.  A total of 6500 apple varieties have been registered.  These old types are called antique apples.  New Jersey was the site of origin of a number of apple varieties.

 Apple in history--The genus name is Malus, which means bad, for the presumed role of the fruit in the fall of man; the idea was that the apple was the forbidden fruit on the tree of the knowledge of good and evil.  But apples did not grow in the Near East when the Garden of Eden was located there.  A climatic change has occurred so they can grow there now.  It's really any body's guess what the apple of the bible really was.

 What are some other apple incidents in history?  Have you heard of William Tell, who shot an arrow at an apple on his son's head.  Then there was the incident of an apple falling on Sir Isaac Newton's head, leading to his important work on gravity.

 The most famous apple-loving American was John Chapman, AKA Johnny Appleseed.  He lived to be 71, from 1774 to 1845.  He is famous for a few things: He walked a long ways alone in ragged clothing through the wilderness mid-West, planting apple seeds.  He was famous for wearing an old sack and a pot on his head, being a kindly vegetarian who sacrificed himself for the good of others.  He had chosen the nursery business for his career, but had a lust for travel.  He had also joined a religious movement, and did some preaching on the side.  In his journeys he lectured on apples, preached, and planted orchards well ahead of the arrival of any settlers, choosing the best sites with his practiced eye.  He wanted there to be food plants around when the settlers arrived.  Many of the orchards later became settlements, and later cities.  Apples were a mainstay of the early settlers, who pressed the apples into juice and made apple cider, which became alcoholic and could be kept over the winter.   Apples could be dried and stored, or made into a jamlike apple butter. 

 Johnny Appleseed planted seeds that he carried with him, which he obtained from cider mills in large quantity.  His trees were highly variable for that reason--apples do not breed true.  In most cultivated orchards, there was uniformity because grafting was used.  In grafting apple trees are cloned--branches are spliced onto a rootstock, which is not allowed to produce any shoots of its own.  Johnny Appleseed did not believe in grafting.  What often happened was that when settlers arrived there were trees bearing fruit, and they could receive grafts.  Also a number of new varieties were discovered by raising seedlings.

 There is more than a little irony in the great success of the Red Delicious apple.  Apple tasters recognize that it has the poorest taste of many apples, with a bitter skin besides.  It's popularity is due to other factors, such as cosmetic appeal, a large red shiny apple is hard to resist. 

 Dwarfing rootstocks--Apple trees get very large and live a long time, to 30 or more feet, which make them hard to pick.  To reduce their size, a series of dwarfing rootstocks have been developed, onto which a graft is made.  They limit the ultimate size of the tree, to 60% or less, even down to 15% of the normal size; it is possible to make mini-dwarf apples, only 5-7 feet tall that bear normal size fruit.

 Figs--Ficus carica, a subtropical tree from w. Asia , and E. Mediterranean , all around Jordan and the Red Sea .  Was one of the most important foods throughout Egypt and Mesopotamia , Palestine .  The grape, date, and olive were the other important crops.

 The fig, along with the date formed the basic diet, either fresh or dried, when people traveled long journeys, they could live on dried figs.  Adam and Eve sewed fig leaves together to disguise nakedness.

In Greece and Italy there were many different varieties with different cultural requirements.  Pliny described 29 varieties of figs.

Figs disappeared from parts of Europe during the Dark Ages, and reappeared in the 14 and 1500s

Most edible figs have an elaborate pollination mechanism that is one of the wonders of nature--

A fig is really a cluster of flowers called an inflorescence.  It is unusual because the flowers are all sealed up inside, and can only be reached by crawling through an opening.  There are three kinds of flowers, male, sterile female, and fertile female.

 1. It involves tiny wasps that mate inside the fruits.

2. Females emerge from the fruit with fertilized eggs inside them and carry pollen from the male flowers of the fig.

3. Female wasps fly to immature figs and enter the fig.  The pollinate female flowers, and lay there eggs in sterile flowers and then die inside the fig.

4. Eggs hatch, with males emerging first, who fertilize the females, still sleeping inside their own flowers.

5.  Males are wingless, and chew open a hole at the end of the fruit with powerful jaws, and then die.

6. Females crawl out, collect pollen and fly off.