Responses of Nouelia insignis Franch (Asteraceae) and Terminalia franchetii Gagnep. (Combretaceae) seedlings to long-term water stress

The responses in terms of seedling growth, biomass allocation and photosynthesis of Nouelia insignis Franch. and Terminalia franchetii Gagnep. to long-term water stress were studied in a greenhouse experiment. Three-month-old seedlings were subjected to the following water supplies for about 79 days: 80, 60, 40 and 20% of field water capacity (FC). The results showed that, as water stress was increased, seedling height, leaf number, root length, specific leaf area (SLA), biomass production and stomatal limitation value (L-s) of both seedlings decreased, and water use efficiency (WUE) increased, and biomass allocation, the diurnal gas exchange and P-n-PAR response curves also altered. Water supply T. franchetii seedlings were much higher than those of N. insignis seedlings. However, T. franchetii seedlings were more vulnerable to long-term water stress than N. insignis seedlings. Simultaneously, N. insignis seedlings had a higher ability to use strong light and a lower ability to use weak light than T. franchetii seedlings. Although water stress had a great impact on their growth, biomass allocation and photosynthesis, both of N. insignis and T. franchetii seedlings displayed considerable water stress resistance, and they tolerated even the most severe water stress (20% FC), and no seedlings died. However, the field conditions were worse; most of them might be hard to get though the long dry season.