Generally, it is the the balance between net photosynthetic carbon uptake (source) and irreversible investments in structures or loss of carbon (sink).
These are carbohydrates that are NOT part of the structural material in a plant, e.g., cell-wall components; these are structural carbohydrates. Non-structural carbohydrates are used for storage and transport, they include sucrose, starch and fructans. I you need a reference, my textbook would be good enough for it: Lambers H, Chapin FS and Pons TL 2008 Plant Physiological Ecology, second edition. Springer, New York.
I am excited see that you have answered my question. I just started reading the section on Growth and Allocation in your textbook borrowed from my supervisor Prof. Kitajima. Your book seems to be an all-in-all textbook for my thesis. Frankly I wanted to mine from the very beginning of this research area. Thank you very much sir.
Hi, Nice to see that you got answer to your question. I did have another plant physiology book that if you want I could share with you. Please send me an email at [email protected]