Editing Chloroplast (section)

==== Starch granules ====

[[Starch granules]] are very common in chloroplasts, typically taking up 15% of the organelle's volume,<ref name="Crumpton-Taylor-2012" /> though in some other plastids like [[amyloplasts]], they can be big enough to distort the shape of the organelle.<ref name="Burgess-1989a" /> Starch granules are simply accumulations of starch in the stroma, and are not bounded by a membrane.<ref name="Burgess-1989a" />

Starch granules appear and grow throughout the day, as the chloroplast synthesizes [[sugars]], and are consumed at night to fuel [[Cellular respiration|respiration]] and continue sugar export into the [[phloem]],<ref name="Zeeman-2007">{{cite journal | vauthors=Zeeman SC, Delatte T, Messerli G, Umhang M, Stettler M, Mettler T, Streb S, Reinhold H, Kötting O |s2cid=15995416 |doi=10.1071/FP06313 |title=Starch breakdown: Recent discoveries suggest distinct pathways and novel mechanisms |year=2007  |journal=Functional Plant Biology |volume=34 |issue=6 |pages=465–73|pmid=32689375 |bibcode=2007FunPB..34..465Z }}</ref> though in mature chloroplasts, it is rare for a starch granule to be completely consumed or for a new granule to accumulate.<ref name="Crumpton-Taylor-2012">{{cite journal | vauthors=Crumpton-Taylor M, Grandison S, Png KM, Bushby AJ, Smith AM | title=Control of starch granule numbers in Arabidopsis chloroplasts | journal=Plant Physiology | volume=158 | issue=2 | pages=905–16 | date=February 2012 | pmid=22135430 | pmc=3271777 | doi=10.1104/pp.111.186957 }}</ref>

Starch granules vary in composition and location across different chloroplast lineages. In [[red algae]], starch granules are found in the [[cytoplasm]] rather than in the chloroplast.<ref name="Rochaix-1998">{{cite book | vauthors=Rochaix JD |title=The molecular biology of chloroplasts and mitochondria in Chlamydomonas|year=1998|publisher=Kluwer Acad. Publ.|location=Dordrecht [u.a.]|isbn=978-0-7923-5174-0|pages=550–565|url=https://books.google.com/books?id=apv1hktfq_8C&pg=PA550}}</ref> In [[C4 plant|{{C4}} plants]], [[mesophyll tissue|mesophyll]] chloroplasts, which do not synthesize sugars, lack starch granules.<ref name="Wise-2006b" />