Re: Are the green parts of plants the only structures that produce oxygen?

In some tree species with green twigs and bark, photosynthesis can occur during
the winter assuming temperatures are favorable and water is available. Many
deciduous trees have young twigs that are green. Some examples of trees with
green bark on their main trunks are striped maple (Acer pensylvanicum), silk
cotton tree (Chorisia speciosa) and quaking aspen (Populus tremuloides). 

Generally, bark photosynthesis seems to be less than or about equal to the rate
of cellular respiration so there would be no net oxygen production but there is
photosynthesis so it would benefit the tree (Brayman and Schaedle 1982; Aschan
et al. 2001). There is a considerable amount of literature on the topic of bark
photosynthesis as indicated by the citations in Brayman and Schaedle (1982). It
has been found that 5 to 40% of total tree photosynthesis could be due to bark
photosynthesis in aspen.

Generally, if a plant tissue is green, it probably can photosynthesize.
Exceptions occur in plants with nongreen leaves such as red Japanese maple,
purpleleaf plum and blue Colorado spruce. Gardeners grow hundreds of plant
cultivars or cultivated varieties with nongreen leaves as novelties. The
nongreen leaves still contain chlorophyll so photosynthesize quite well. The
leaf color is determined by anthocyanins which obscure the green chlorophyll. 

Even nongreen stems may have green tissue beneath the bark. It seems logical
that those cells can photosynthesize. 

In some orchids, the green roots photosynthesize. Some cacti and other plants
have green stems that conduct virtually all the photosynthesis. 


References


Aspen photosynthetic trunks


Brayman, A. A. and Schaedle, M. 1982. Photosynthesis and respiration of
developing Populus tremuloides internodes. Plant Physiol. 69: 911–915.


Pearson, L. C. and Lawrence, D.B. 1957-58. Photosynthesis in aspen bark during
winter months. Proceedings of the Minnesota Academy of Science 25-26: 101-107.


5 to 40% of aspen tree photosynthesis due to bark photosynthesis


Green bark of striped maple (Acer pensylvanicum)


Green bark of silk cotton tree (Chorisia speciosa)


Green bark of silk cotton tree (Chorisia speciosa)


Photosynthetic Orchid Roots 

Pfanz, H., Aschan, G., Wittmann, C. 2001. Bark photosynthesis: Fact – not
fiction. In: Labrecque, M. (ed.): L´abre – The tree 2000, IQ Collectif,
Montreal, Canada, S. 117-121.


Aschan, G., Wittmann, C. and Pfanz, H. 2001. Age-dependent bark photosynthesis
of aspen twigs. Trees - Structure and Function. 15: 431-437.