D O P LANTS B REATHE ? Well, the answer to this question is not quite so direct. Yes, plants require O for respiration to occur and they also give out CO . Hence, plants have systems in place that ensure the availability of O .
Plants, unlike animals, have no specialised organs for gaseous exchange but they have stomata and lenticels for this purpose. There are several reasons why plants can get along without respiratory organs. First, each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.
Second, plants do not present great demands for gas exchange. Roots, stems and leaves respire at rates far lower than animals do. Only during photosynthesis are large volumes of gases exchanged and, each leaf is well adapted to take care of its own needs during these periods. When cells photosynthesise, availability of O is not a problem in these cells since O is released within the cell.
Third, the distance that gases must diffuse even in large, bulky plants is not great. Each living cell in a plant is located quite close to the surface of the plant. ‘This is true for leaves’, you may ask, ‘but what about thick, woody stems and roots?’ In stems, the ‘living’ cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels.
The cells in the interior are dead and provide only mechanical support. Thus, most cells of a plant have at least a part of their surface in contact with air. This is also facilitated by the loose packing of parenchyma cells in leaves, stems and roots, which provide an interconnected network of air spaces. The complete combustion of glucose, which produces CO and H O as end products, yields energy most of which is given out as heat.
C H O H O Energy → If this energy is to be useful to the cell, it should be able to utilise it to synthesise other