Transpiration/Evaporation Ratio in Prunus Fremontii and Marianna 2624 over a 4-Day Period of Drought

Drought stress represents one of the major environmental limitations to crop production in a large portion of the Earth’s surface. Natural genetic resources are one of the most powerful weapons against environmental stress. In such contest, the behavior in terms of water loss of two species, P. fremontii (slower-growing) and Marianna 2624 (faster-growing), native to arid and humid regions respectively, was tested. Transpiration (T) and evapotranspiration (ET) rates and soil water content (SWC) were measured in the two species under controlled conditions. Evaporation rate from the soil surface was obtained by difference, and an average transpiration/evaporation ratio (T/E) was calculated to determine the relative importance of the two processes. Soil water content decreased linearly in both species over the 4-day period, however only Marianna 2624 ET decreased along with SWC. On the contrary, T and ET of both species correlated positively with temperature, indicating a more direct response at the leaf level. A much higher T/E in Marianna 2624 than in P. fremontii also indicated that water was lost mainly by T in the faster-growing species, while evaporation from the soil surface was the predominant process of water loss in the slower-growing species.