Photosynthetic Induction Phenomena in Plants of Various Light Habits
Changes in photosynthetic rates and duration of photosynthet ic induction were studiedin plants of various light habits，Such as Alocasia macrorrhize（shade－loving），Coffea arabica（hemishade－loving）and Hevea brasiliensis（light loving）separately exposed under different pho-ton flux density（PFD）and extreme PFD. The fesults showed that photosynthetic induction ex-isted in all the three plants. Different plants demanded different optimum PFD and maximum rateof photosynthesis（Amax），which were both the lowest in A，macrorrhize，the highest in Heveabrasiliensis and medium in Coffea arabica.When exposed under optimum PFD,A. macrorrhizehad the shortest duratfon of induction，Hevea brasiliensis，the longest and Coffea arabica， medi-um. Comparison of the duration ratios of rapidvariation to induction among the plants exposed un-der their optimum PFD revealed that the ratio was the highest in A. macrorrhize（31 ％），the low-est in Hevea brasiliensis（3．8％）and medium in coffea arabica（16．7％）．The response of theplants to extreme PFD indicated that A. macrorthize was adaptable to low PFD（20μm~(-2)·s~(-1)）and sensetive to high PFD（1500μE·m~(-2)·s~(-1)），which was contrary in Hevea brasiliensis.A. macrorrhize was adaptable to weak light and Hevea brasiliensis was adaptable to stronglight，which was the photosynthetic characterisitics of the plants of various light habits formedthrough long－term adaption to environment．Besides having lower light compensation point，A.macrorrhize has formed the mechanism to capture light energy rapidly under weak light within ashort time.