A study was carried out to investigate the effect of temperature and light intensity on the photosynthetic rate of young pepper plants, and to know the characters of photosynthesis under the continuous illumination. The results were summerized as follows.
1. Photosynthetic optimum temperature of young pepper plant was higher under the high light intensity rather than under the low light intensity at temperature ranging from 5℃ to 35℃.
2. Photosynthetic rate was gradually increased till 25℃ under the high light intensity above 30 Klx, but the rate was rapidly decreased at high temperature above 25℃. And $quot;Kimjang-gochu$quot; was taken less the influence of temperature than $quot;Sae gochu$quot; and drawed a dull mono-peak curve. Under the low light intensity of 5 Klx and 10 Klx, the photsythetic rates between the both variety were different, however, it seemed that photosynthetic rate was higher in low temperature condition than in high temperature condition.
3. It was suggested that the growth (photosynthetic) optimum temperature of pepper plant was 20-25℃, and the saturating light intensity at 20℃ was about 40-50 Klx.
4. Considering the photosynthetic characters mentioned above, $quot;Sae-gochu$quot; was fit for early cultivation and $quot;Kimjang-gochu$quot; for common field cultivation.
5. It would have to be examined more carefully that photosynthetic rates of young pepper plant seemed high at low temperature which was not suitable for growth. But it was assumed that a little lower temperature was fit for the cultivation of pepper plants during the period of low light intensity.
6. The increase of respiratory rate was slow at 5-25℃. but increased rapidly at 35℃: 4.86㎎ CO₂/d㎡/hr and 3.45㎎ CO₂/d㎡/hr in $quot;Sae-gochu$quot; and $quot;Kimjang-gochu$quot; respectively. There was high correlation between the respiratory rate and the decreasing photosynthetic rate.
7. It seemed that photosynthetic rate was decreased in 7-8 hours after measurement (23-24 o´clock) and recovered later.
Therefore, it was suggested the time of supplementary illumination at seedling stage must be decided under the consideration of results mentioned above.
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