Re: What determines the number of seeds in a mandarin?

Hello Katherine,

Your question does not have a simple answer! 

The number of seeds in a mandarin orange depends on the number of ovules 
in the flower that are fertilized. An ovule is the part of the plant that 
contains the egg cell. The number of ovules in the flower depends on the 
tree variety. There are a cluster of several genes which determine the 
number of ovules that the flower would produce. 

A note about genes- just like in humans (and in all other living things), 
all of the cells that make up a tree would have the same genes. These 
genes are the same ones from the pollen and the egg cell (also called an 
ovum). When the ovum is fertilized by the pollen, the ovum then begins to 
develop into a seed. The fertilized ovum is the cell which contains a 
complete set of genes that will guide the development of a new plant. 
This cell will make a copy of the set of genes, split into two cells, 
each with the same set of genes. Then these two cells will each make a 
copy of the set of genes, split into two cells, again, each with the same 
genes. This copying and splitting of the cell is already being directed 
by the genes! Even when the cells differentiate, as in when the cells 
start to take on the different shapes of the plant cells, each cell still 
contains the same set of genes. 

***What I have just written is a very simplified idea of how cells and 
genes are made in plants. This is much much MUCH more complicated with 
polyploidy and haploidy rampant in the plant world.***

There are plant cells that differentiated into the flower cells, and 
other cells that differentiated into the ovule and ovum cells. The genes 
that guided the development of the cells into the flower, ovule and ovum 
are from the same set of genes that came from that original fertilized 
ovum!

As for the number of fruits to be produced on a mandarin tree, that is 
not the same as what happens with a human female. A baby girl is born 
with all of the egg cells already formed. Her hormones will guide each 
egg cell to develop into an ovum every month once her body is mature 
enough. A tree does not have all of the egg cells already formed. These 
occur every season, when the tree produces flowers.

I hope that I have ironed out some of your questions!
Keep asking!

Evelyn

References:
*These are references that I used to answer your question. You can link 
onto them, but I do not know if they will be easy to read!*

Link to a detailed description of several varieties of mandarin orange: 
http://www.hort.purdue.edu/newcrop/morton/mandarin_orange.html#Des
cription

Link to a detailed description of cell division and differentiation http://
web.ukonline.co.uk/webwise/spinneret/life/celdiv.htm

Link to university-level descriptions of plant growth and flowering: http://www.biologie.uni-hamburg.de/b-
online/e28/28c.htm http://gears.
tucson.ars.ag.gov/book/chap5/citrus.html

Link to definition of polyploidy: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Polyploidy.
html

Link to definition of haploidy: http://www.fact-
index.com/h/ha/haploid.html