If seeds don't perform photosynthesis why do they accumulate chlorophyll? There is also a strong correlation between chlorophyll content and longevity of seeds during development.
First, respiration is NEVER a source of sugars. Sugars are consumed in respiration, and thus provide energy.
Second, I do not necessarily believe seeds do not perform photosynthesis; if they are green they probably do. I would measure it, before jumping to conclusions. That may then offer you an explanation for the correlation you refer to.
I expressed my idea wrong when I said sugars, what I meant was energy in that case. Thanks for the reply.
Yes, that makes a lot more sense. The rest of my response, about chlorophyll and photosynthesis, still stands, of course.
I talked to a friend about this question and, apparently, developing green seeds are photosynthetically active. A guy called Giovanni Finazzi, if I am not wrong, measured it in Arabidopsis seeds inside siliques. The main thing about his findings was that those seeds were mainly doing cyclic photosynthesis not fixing carbon but producing ATP instead. The reasons for that could be many. For example, lack of proper light (Blue/Red balance), CO2 diffusion into the seeds and or the tissue "preference". That is all not clear. It is still puzzling for me that a tissue that is buried inside a fruit and almost do not receive light has to have a developmental phase which is rich in chlorophyll.
Pea seeds inside a pod are green. The issue to consider is: how much light actually does penetrate where those chloroplasts are? Probably as much as in a thick shade leaf of Schefflera arboricola, og which I show images in my textbook (see attached). Interesting question!
The fruit can receive light and have photosynthesis.
Here are some references about fruit's photosynthesis:
C. T. Phan. 1970. Photosynthetic activity of fruit tissues. Plant & Cell Physiol. 11, 823-825
A. W. Whiley, B. Schaffer and S. P. Lara. 1992. Carbon dioxide exchange of developing avocado (Persea americana Mill.) fruit. Tree Physiology 11, 85-94
L. F. M. Marcelis and L. R. Baan Hofman-Eijer. 1995. The contribution of fruit photosynthesis to the carbon requirement of cucumber fruits as affected by irradiance, temperature and ontogeny. Physiologia Plantarum 93, 476-483.
J. Bower, B. D. Patterson and J. J. Jobling. 2000. Permeance to oxygen of detached Capsicum annuum fruit. Australian Journal of Experimental Agriculture 40, 457–463
E. D. Barrera and P. S. Nobel. 2004. Carbon and water relations for developing fruits of Opuntia ficus-indica (L.) Miller, including effects of drought and gibberellic acid. Journal of Experimental Botany 55, 719- 729
Previous studies, within about 428 kinds of seeds contain chlorophyllous embryo(Dahlgren, 1980; Yokovlev and Zhukova, 1980). But, we do not know that the synthesis of chlorophyll at chlorophyllous embryo is light or dark synthesis. It is a very interesting question. We did a similar experiment on soybean. The proportion of light to penetrate the seed coat is high.
R. Dahlgren. 1980. The taxonomic significance of chlorophyllous embryos in angiosperm seeds. Bot. Notiser. 133, 337-341.
M. S. Yokovlev and G. Y. Zhukova. 1980. Chlorophyll in embryos of angiosperm seeds, a review. Bot. Notiser. 133, 323-336.
In connection with the previous discussion the question arises: anybody had determined or could determine the number, location and status of photosynthetic elements during seed germination or buds swelling? Modelling shows that the photosynthetic elements can be placed in separate groups by two per group in seedling. In course of germination number of active groups must increase.
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