Effects of Ozone on the Growth of Radish Plants at Different Temperatures
1988 Volume 23 Issue 4 Pages 209-217
Details
1988 Volume 23 Issue 4 Pages 209-217
Radish plants (Raphanus sativus L. cv. Comet) were grown at 20/13°C, 25/18°C and 30/23°C (day/night) for 18 days after sowing. The plants were exposed to ozone (O3) at 0. 1 ppm (v/v) for 4 hrs a day for 7 days from the 11th to 17th day after sowing. The dry weight growth of the plants grown at 25/18°C and 30/23°C was significantly reduced by 20% by the exposure to O3 for 7 days. However, the dry weight growth of the plants grown at 20/13°C was not affected by the exposure to O3 for 7 days. The results of growth analysis suggested that O3-induced inhibition of dry weight growth is mainly due to the reduction in net assimilation rate.
Effects of 0.1ppm O3 on net photosynthetic rates were examined for the plants grown at different temperatures. Net photosynthetic rates were measured at respective daytime temperatures under 1, 800, μmol·m-2.s-1 (60 Klux). Net photosynthetic rates of the plants grown at 25/18°C and 30/23°C were reduced by theexposure to O3 for 4 hrs by 10.8% and 13.5%, respectively. Net photosynthetic rate of the plants grown at 20/13°C was not reduced by the exposure to O3. The inhibition rates of net photosynthesis during exposure to O3 for 4 hrs and the inhibition rates per unit O3 absorption of net photosynthesis were ranked as follows: 30/23°C≥25/18°C<20/13°C
It is concluded that the increase of O3-induced reduction in dry weight growth at relatively high temperatures (25/18°Cand 30/23°C) is mainly due to the greater inhibition of net photosynthesis at high temperatures.
