I have some questions about how a large change in size might affect a chloroplast. I have reasons to believe that somehow this change in chloroplast size results in a cell signal that turns on a developmental gene that I am interested in.

I am working on an photosynthetic organism (Volvox carteri, a multicellular relative of Chlamydomonas reinhardtii) that undergoes a lot of cell divisions in short succession during embryogenesis. A large reproductive cell (55 um diameter) divides into about 2000 much smaller cells (3.3 um diameter). Most of of each cell (before and after embryogenesis) is filled with a single chloroplast. The small cells have a similar morphology to Chlamydomonas reinhardtii.

Now I am curious to know what changes in a small compared to a large chloroplast. Assuming for simplicity sake a sphere, one obvious answer is that the surface-to-volume ratio is higher in a small than in large chloroplast (16 fold).

But how does this change in size affect the thylakoid membranes? Since grana are stacks of membranes they are rather like 3 dimensional objects inside the chloroplast, while lamellae would be more like 2 dimensional objects. (I do not know if I apply the concept of fractal dimension here correctly since my understanding of complexity research is on the level of popular science books, but I would say the fractal dimension of grana should be higher than for lamellae).

So analogous to a increase in surface-to-volume ratio from a large to a small chloroplast, I would predict that the lamellae-to-grana ratio also increases.

So my questions are:

1) Is my prediction correct that the lamellae-to-grana ratio should increase from a large to a small chloroplast?

(Or is my prediction just my haphazard application of long-forgotten high school math?)

2) What effect would an increase in lamellae-to-grana ratio have? Might it change the chloroplast redox poise in the dark?

(e.g. since PSI is mostly located in lamellae and PSII in the lamellae the grana, the PSI-to-PSII ratio would also change)

3) Do you have any other suggestions what might change inside a chloroplast due to a change a large to a small size? I would be especially interested to changes in the chloroplast in the dark.

(e.g. the ratio of membrane bound proteins involved in electron transport to electron acceptors in the stroma increases; might this affect the redox poise of the chloroplast in the dark? )

4) Could the drastic change in chloroplast size result in some sort of stress? How?