Effects of drought stress on chlorophyll a fluorescence in two rubber tree clones

- A significant difference in leaf water potential between two rubber tree clones was observed at 38 days after water deficit (DAWD).
- In the FX3864 clone, the appearance of positive L- and K-bands occurred at 36 DAWD.
- At 36 DAWD, F0 values were significantly higher in FX3864 than in the control.
- The two rubber tree clones differed in the plasticity of their response to drought and rewatering.
- The RRIM600 clone showed an advantage over the FX3864 clone in low rainfall regions.

This study compared the photosynthetic responses of two clones (RRIM600 and FX3864) of the rubber tree (Hevea brasiliensis L.) subjected to drought stress. This stress was imposed by complete removal of watering until the leaf water potential (Ψw) reached critical values, which occurred at 38 days after water deficit (DAWD) for both rubber clones. One-year-old rubber plants were cultivated in 20 L pots filled with a soil:sand:humus ratio of 4:3:3. Photosynthetic performance was analyzed by measuring chlorophyll a fluorescence transients at 0, 28, 36, and 38 DAWD. The photochemical process was altered to some extent following water deficit. A decrease in Ψw was observed for both rubber clones at 36 DAWD. The FX3864 clone was more susceptible to drought and showed a deficiency in photosynthetic electron transport. The RRIM600 rubber clone showed an advantage over the FX3864 clone in terms of stability and efficiency in utilizing energy in low rainfall sites.