How exactly do oranges with seeds reproduce? What is the purpose of the bubbles inside the sections?

Question

How exactly do oranges with seeds reproduce? What is the purpose of the bubbles inside the sections?

Answer 1

The fruit of the orange, or other citrus, is dropped by the tree once it is ripe, if left to mature naturally. This happens in the cool, wet winter months in the subtropics where citrus trees are native. However they are usually eaten by birds or animals first. The bright color was to attract fruit-eating birds who will eat the seeds with the fruit. The birds fly away and leave the seeds in a new location so act to spread the trees' seeds into new territory. The tree attracts the birds by color to signal there is a reward. The birds co-evolved with the fruit tree to act for the plant and be paid for the service. This is true for all fleshy fruit though not all depend on birds some fruit seeds are spread by mammals.

This ability to survive being eaten explains how the bitter orange was brought to South America but became naturalized there 400 years ago.

http://www.jstor.org/pss/3038017

http://www.jstor.org/pss/2461256

http://www.jstor.org/pss/3565617

http://www4.gu.edu.au:8080/adt-root/uplo...

The bubbles in each section are the pulp vesicles. The orange segment is called a locular cavity that grows into a sac filled with thin walled cells with watery juice, the pulp vesicles.

There are primitive forms of the citrus family of trees that show less structure and specialization in the pulp vesicles.

In them there may be few pulp vesicles in the locule sac because the space is taken by the very large seeds that almost fill the locules.

The citrus has been selected over centuries of cultivation, since before 300 BC in China, for more pulp and fewer, smaller seeds.

http://books.google.com/books?id=SmRJnd7...

Answer 2

Oranges, like all other fruit trees, reproduce using their seeds.  How do they do this? Naturally, trees "drop" their fruits when it's in the right age, and the fruits on the ground naturally becomes the fertilizer for the seeds inside them.  The tiny bubbles that are the edible parts of the fruit are actually the undeveloped seeds.  As time grows these bubbles become seeds of the orange.  Some never develop, and becomes a nutrient sustainer for the seeds themselves.