Re: Does every chloroplast in a plant undergo photosynthesis?

According to this online biology textbook: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PlantCell.html

A typical plant cell contains 20-40 chloroplasts.  The number of cells in 
a leaf, or leaves in a plant varies greatly based on the species.

Keep asking questions!

-Marcy LaViollette



David R. Hershey adds the following:

The light reactions and the Calvin cycle can be separated experimentally in 
the 
Hill reaction.

There are several situations where some leaves on a tree may not be conducting 
net photosynthesis while others are. Leaves on the upper, outside parts of the 
canopy get more light so would start photosynthesis earlier in the day after 
sunrise than leaves deep in the canopy that are shaded.

On the other hand, leaves at the top of the canopy would close their stomata 
earlier if the tree was water stressed, as often happens in midday of hot, 
summer days. If the stomata close, net photosynthesis would be zero due to 
lack of carbon dioxide gas. Leaves deep in the canopy would not be subject to 
as much water stress as quickly because their transpiration would be so much 
lower.

In shade plants on the forest floor, parts of a leaf may intermittantly be 
exposed to high light via sun flecks. The chloroplasts hit by sunflecks could 
have net photosynthesis, while those not exposed might not have net 
photosynthesis.

In mineral nutrient deficient leaves, some parts of the leaf lose chlorophyll 
(become chlorotic) so would not photosynthesize.

Reference


Relative enhancement of photosynthesis and growth at elevated CO2 is greater 
under sunflecks than uniform irradiance in a tropical rain forest tree 
seedling