Why do plant leaves turn yellow?

Question

Why do plant leaves turn yellow if they don't get enough water or get too much water? I want to know the process. I've been searching in Google for an explanation, but none of the sites did. Please describe the process.

Answer 1

It's all about the chlorophyll. When chlorophyll production decreases for any reason (including the plant saving energy and responding to stress from dehydration, or not having the right nutrient balance to fuel the production), the green goes away. These two resources can describe the process more in depth:

https://homeguides.sfgate.com/leaf-turning-yellow-physical-chemical-change-104665.html

https://harvardforest.fas.harvard.edu/leaves/science