Ecophysiology of Pilocarpus microphyllus in response to temperature, water availability and vapour pressure deficit

Abstract

The jaborandi is a natural source of alkaloids used in the treatment of important diseases and, therefore, relevant for the pharmaceutical industry. However, the lack of information on the jaborandi ecophysiological responses under different climatic conditions is the major limitation for its expansion in Brazil. Thus, we investigated the effects of different environmental conditions on the ecophysiology of jaborandi seedlings, combining several ranges of mean air temperature (T), vapour pressure deficit (VPD) and water availability. For this, jaborandi seedlings were cultivated in four different environments: cold and humid (Temp: 21.1 °C, VPD: 0.31 kPa), hot and humid (Temp: 26.8 °C, VPD: 0.34 kPa), hot and dry (Temp: 26.3 °C, VPD: 1.09 kPa) and cold and dry (Temp: 20.8 °C, VPD: 0.84 kPa); all the environments had two water availability levels: well-watered (control: C) and water-stressed (45% of the maximum substrate water holding capacity). Growth and fluorescence parameters, crop water stress index and enzymatic antioxidant activity were evaluated. Our results revealed that the seedlings reduced their growth when subjected to water restriction in all treatments, resulting in a lower total dry mass production, mainly due to the reduction of the root system. In the well-watered treatments, jaborandi seedlings showed higher growth when cultivated in warmer environments, regardless of the VPD. Under low-temperature conditions, there was a reduction in maximum quantum yield efficiency of PSII, indicating damage to photosystem II; also, the minimum fluorescence and the enzymatic antioxidants activity increased. The highest dry mass accumulation was obtained when the seedlings were submitted to high temperatures, indicating that the regions that experience such conditions are the most suitable for jaborandi cultivation.