CAM plants require special treatment

CAM plants are a group of plants that only assimilate at night and grow slowly. The cultivation of these plants requires special treatment.

CAM plants naturally grow in climates that are usually hot and dry. To avoid drying out, they only open their stomata at night to allow CO2 inside for the assimilation. They bind the CO2 and store it as malate. Nothing else happens at that stage and besides, the storage capacity is limited: at some point the plant is full. In daylight they keep their stomata tightly closed. The stored malate is transported to the leaves where it is converted into sugars during the photosynthesis process. This can only take place during the day: photosynthesis requires energy from the sun.

This special way of assimilation may be a good adaptation to natural conditions, but not really  efficient. These plants grow very slowly which is inconvenient in a greenhouse. Slow growth costs money. Well-known CAM plants are cacti, succulents, bromeliad species and thick-leaved orchids, to which the much-cultivated Phalaenopsis belongs.

Kalanchoe plant


Some of these species are very strictly CAM plants, others can sometimes also switch to the ‘normal’ way of photosynthesis (known as C3) and thus assimilate during the day.Young leaves of the Phalaenopsis, for example, have C3 characteristics; the older ones function in the CAM way. The young Kalanchoe blossfeldiana plants are C3, the older ones CAM; thus at some stage a transition takes place which can be delayed through taking cultivation measures.

Furthermore, breeders often select on productivity and for CAM plants this means that specimens with C3 capacities are favoured. This is most visible in Phalaenopsis. Many species no longer behave as typical CAM plants, but are capable of assimilating during part of the day. At some point they close their stomata again. The cultivation of such plants requires much insight into the characteristics of the specific variety. Giving CO2 only makes sense when the stomata are open, and illumination when the plant is photosynthetically active. In fact, a different cultivation recipe applies to each species and variety.

Allow more light

Because Phalaenopsis, Kalanchoe, Bromeliad species and others are often no longer strictly CAM plants, it could make sense to allow them more light, and this development shows up in practice. It is also very useful to make the light diffuse with ReduFuse during the season as it gives a better light penetration even in compact plants, which will result in more active leaves. Later in the season the light can be tempered with one or more layers of coating such as ReduSol.

Light colour

A new insight is that the light colour plays a role in the transition of C3 to CAM characteristics in plants that change with age. A reduced amount of blue light ensures a later transition. Insight in this still has to grow for practical application. With Phalaenopsis, the ratio of red/far red radiation also plays a role in the tendency to produce flower branches. High levels of red encourages this process, which would justify the application of ReduFuse IR in the cooling phase (when the branch induction takes place). It is essential to customize this per species and variety.

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