Hi Huan

Considering that different plant species (shade tolerant or not tolerant) do not respond in the same way against different shading levels, in general the shading of plants causes: 1) decrement of the dry mass productivity, 2) increment of the plant height, 3) decrement of the photosynthetic rate 4) increment of the photosynthetic pigments.

For more details you can see the paper below.

Depending on whether the plants are shade  or sun loving, there could be dramatic effects on the physiological process and overall plant performance. However, we can generalize  the effects of shading in the following ways:

1. shading will affect leaf area which has direct relation to production

2. Decrease in growth rate

3. the plant height will often increase as in etiolated plants, and

4. will see reduced general vigour and in case of dragon fruits, the plants might become brittle due to reduced metabolism and other processes....

These are some  directs but there could be many more depending on plant species.

Thank you both. In my experiment i worked with stems under poly-shade mesh of 30% and 60%, and they haver better response (in terms of new stems appearing and growing) that the control stems (with no shading), why could be that ?

Mr. Calero,

Apart from the responses of plants to shading which were already mentioned (by Mr. Zervoudakis and Mr. Chhogyel), in addition, shading can cause decreased flowering (general rule) and increased specific leaf area. Regarding the better response of plants to shading, in terms of the appearance and growth of new stems, as you referred, please have in mind that plants adopt their strategy in order to increase their competitive ability under reduced light regimes. The latter may help you to interpret your results. Also, the attached files may be useful to your research.

I wish you quick progress in your research. 

Best Regards,

A. Matsoukis

Article Environmental conditions and drenched-applied paclobutrazol ...

Article Mepiquat chloride and shading effects on specific leaf area ...

Article Leaf Area Response of Lantana camara L. subsp. camara to Pla...

Article Growth and Flowering of Lantana camara L. subsp. camara as A...

Article Impact of shading and chlormequat chloride on Lantana specif...

Article Response of Lantana camara L. subsp. camarato paclobutrazol ...

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Mr. Juan, Dragon Fruit is a sun loving crop being an cactus it is expected that it will remain more in erect condition in sunny situation. As you suggested that you got more branching in shaded condition, I expect the branches must have been longer and thin compared to that in the sunny condition to overcome its photosynthetic need. Kindly let me know if my assumptions are true.

Mr. Matsoukis and Mr. Mohan, thank you for your contributions, they helped a lot. The new stems were longer and thin than the others exposed to sunlight, and also there was more branching at shadow conditions. It helps a lot to get fast planting material.

Mr. Juan, although you got very fast planting material, take care you wont overshadow them, otherwise after few months of such exposure your mother block will only have weak branches left. Better way is remove the shade net after a few days or months and allow sufficient sunlight to reach the plant.

If you are doing a nursery business, sapling with new weak branches you may end up failing to get premium prices for the plant. So, after the roots are initiated make them exposed to sufficient sunlight, so that it looks in good condition.

Thank You

 Green plants produce shade by absorbing sunlight to invest as energy in photosynthesis to produce sugar. They also actively transpire, producing an additional cooling effect. In gardening terms, there are various types of shade: Full sun - more than five hours of direct sun per day. Part shade - two to five hours of direct sun, or all-day dappled sun (sunlight shining through open trees). Full shade - less than two hours of direct sun per day... Under a dense forest canopy, light intensity can be very low. Special adaptations produce the shade tolerancethat allows plants to survive in the understory. In addition, shade within a canopy can elicit shade avoidance responses whereby plants elongate their shoots in order to reach light for optimal photosynthesis.