Low foliar construction cost and strong investment in root biomass in Calotropis procera, an invasive species under drought and recovery

Abstract

The relationship between uptake and use of resources has always been highlighted among functional traits to explain the performance of invasive and native species. However, previous studies have shown that, under resource limitation, the species of both groups tend to have similar functional behavior. We measured a group of resource-use traits under controlled drought stress in Cenostigma microphyllum native to Caatinga of Brazil and the invasive species Calotropis procera that has a large occurrence in semiarid regions. The results showed that invasive well-watered plants always had higher CO2 assimilation rates and lower leaf construction costs than native plants, while stomatal conductance was similar. On the other hand, under water deficit conditions, the invasive plants tolerated more days of drought and showed higher root/shoot biomass ratio, leaf relative water content, lower leaf construction costs and payback time than the native species. Moreover, seven days after stress, the invasive plants displayed higher CO2 assimilation, photosynthetic nitrogen use efficiency, instantaneous efficiency of energy use and lower leaf construction costs compared with the native species. The ability to acquire and distribute resources among the different plant tissues at the right time seems to be a fundamental combination for the plants used in the experiment. Thus, a more acquisitive strategy is fundamental for having enough carbon to invest in the root biomass in C. procera under drought, which could contribute to maintain higher leaf water status for longer time compared with C. microphyllum.