Effects of (2 Chloro-Ethyl) Trimethlammonium Chloride on Plant Growth, Leaf Area, and Net Assimilation Rate

Both under glasshouse conditions and in a constant environmentwith light from fluorescent tubes, mustard plants' treatmentwith (2 chloro-ethyl) trimethylammonium chloride (CCC) respondedby an increase in total leaf area. In the glasshouse the increasewas due to the production of more lateral leaves, and in thegrowth chambers to the enlargement of stem leaves, since lateralbranches did not form. Despite the increase in area, the netassimilation rate fell; this may be attributable to an effectof CCC on the photosynthetic mechanism or to an increase inthe mutual shading of leaves, but it is more probable that theinhibition of stem growth also caused by CCC decreases the demandfor photosynthate and leaves photosynthesise less. The leafarea of mustard (a long-day plant) is increased also by short-daytreatment, and here again there is a concomitant shorteningof the stem. Chlorophyll content, both per leaf and per unit area, and totaldry matter per unit area, were increased in tobacco plants grownin culture solutions containing CCC. The treatment affectedthe distribution of nitrogen, increasing the amount per leafand decreasing it per stem.