I made an experiment with several tomato cultivars. I measured chlorophyll content at one middle leaf by using SPAD 502. The result showed that plant with dense leaves (high number of internodes) had lower chlorophyll contents compared to the ones with less dense leaf (Lower number of internodes).
Hi, but which leaf you measure ? could it be possible that, the different defense leaves received different light intensity
In dense canopies usually there is more shading by leaves from upper levels. In such situations the photosynthesis parameters of the shaded leaves are lower than the top leaves that face to full light. We can expect due to lower light intensities the chlorophyll level are lower than full light exposed leaves.
The best
Sasan
It is possible that dense leaves are thinner and therefore show less chlorophyll values in comparison to less dense leaves that are thicker and therefore show more chlorophyll, as SPAD measures chlorophyll as a result of absorbance of particular wavelengths. You need to confirm this using chemical chlorophyll analysis
Shaded leaves are usually thinner and chloroplast distribution is different between sun leaves (chloroplast are mostrly in palisade layers) and shaded leaves (chloroplasts located in palisade and spongy parenchyma).
I am not sure if it is also true for plant exposed to a high sun radiation due to the fact that high radiation could cause chlorophyll degradation.
It depends on plant species since PAR ranged from 100 ftC to 3000 FtC. Besides light intensity not only modified photosynthesis system, it alter the leaf anatomy as well
The plants all synthesized roughly the same amounts of chlorophyll and subsequently distributed it amongst the volume of leaves present. The fewer or smaller the leaves, the higher the concentration of chlorophyll and the higher the SPAD value will be. Leaves in shade over-compensate by housing more chloroplasts in order to take advantage of the PAR, while leaves in full sun are more diluted, because their needs are satisfied and they must employ more energy on water transfer (cooling) and a protective waxy cuticle (UV protection).
Plant has dense canopies usually being more shaded by leaves from upper side. That trigger different rate of photosynthesis between lighted leaf and covered leaf. The upper side leaf provide better amount of photosynthesis products than shaded leaf which it also has higher total number of covered leaf than lighted leaf. The shaded leaf is not only becoming a producer but also consuming higher carbon complex to maintain their life.
The higher respiration rate than photosynthesis rate which also lead to chlorophyll breakdown to provide more energy and also transport mobile element such as Mg, P, N directly to new leaf. It has been believed that dicotyle plant which have sympodial growth provide more leaf to maintain the stability between production and consumption of carbon complex.
This is a paradox
This is true for 1cm3 size of leaves, since light manipulate leaves of the same species, where under low light intensities created by dense leaves the leaves being of higher leaf area on the account of thickness. In contrast, leaves under high light intensities are thicker and less area. Therefore, when you compare you have to make the sample represent a complete leaf. and thus you can detect the differences between light intensities. Besides, in photosynthesis is highly dependent upon Ribisco activity
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