Crassulacae Acid Metabolism in Cactus and Succulents ... 1/3

Introduction

Nearly all plants breathe through stomata (little holes) in the leaves (or stems in succulents) taking in Carbon dioxide (CO2) from the atmosphere, combining it with water (H2O) in the presence of chlorophyll (the green stuff!) and enzymes, using sunlight as the energy source for the manufacture of the sugars (CHO), releasing oxygen (O2) into the atmosphere as a by-product of the chemical process known as photosynthesis, (we humans and other members of the animal kingdom do the reverse - take in oxygen to burn sugars and release energy, and release Carbon dioxide as a by-product).

It was always thought that all plants photosynthesised the same way, but then it was discovered that there are at least three different pathways in which photosynthesis can occur to achieve the same end result (manufacture of sugars for growth), namely:
C3 ('normal'), C4 (high temperature/high water/high light availability), and CAM (high temperature/low water availability).
All plants use C3, but then some also use C4, and then still others use all 3. If they use more than one pathway they may do this either in different areas of the plant or at different times of the day.

Crassulacae Acid Metabolism

Romans or Geeks of old noticed that certain fleshy plants like sedums tasted "sour" in the morning and less "sour" at night, what they were unknowingly observing was Crassulacean Acid Metabolism .

Crassulacean Acid Metabolism (CAM) was first researched in the 1800's in the Crassula family, hence it's name.

CAM has evolved from normal photosynthesis independently many times (20 families of land plants have it) over the past 100 million years and is present in more than 20,000 species of plants including the cactus family and other succulents. There is a strong connection between CAM and succulence, like one needs the other in other to facilitate survival of the plant.

Families with CAM include Agavacea (agaves), Cactaceae (cactus or cacti), Crassulaceae (crassula), Euphorbiaceae (euphorbia), Liliaceae (lillies), Orchidaceae (orchids) and Vitaceae (grapes).

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