Abstract

The evergreen C3 plant Calotropis procera is native to arid environments. Thus, it grows under high vapor pressure deficit (VPD), intense light, and severe drought conditions. We measured several ecophysiological traits in C. procera plants growing in semi-arid and seacoast environments to assess the attributes that support its photosynthetic performance under these contrasting conditions. Gas exchange analysis, primary metabolism content, nutrients, the antioxidant system, and leaf anatomy traits were measured under field conditions. In the semi-arid environment, C. procera was exposed to a prolonged drought season with a negative soil water balance during the 2 years of the study. Calotropis procera plants were exposed to a positive soil water balance only in the rainy season in the seacoast environment. The leaves of C. procera showed the same photosynthetic rate under high or low VPD, even in dry seasons with a negative soil water balance. Photosynthetic pigments, leaf sugar content, and the activity of antioxidant enzymes were increased in both places in the dry season. However, the anatomical adjustments were contrasting: while, in the semi-arid environment, mesophyll thickness increased in the driest year, in the seacoast environment, the cuticle thickness and trichome density were increased. The ability to maintain photosynthetic performance through the seasons would be supported by new leaves with different morpho-anatomical traits, with contrasting changes between semi-arid and seacoast environments. Furthermore, our results suggest that an efficient antioxidative system and leaf sugar dynamics can contribute to protecting the photosynthetic machinery even under severe drought.

Highlights

  • Changes in global rainfall patterns have resulted in more frequent drought across the semi-arid environments of the world (IPCC Climate Change, 2018)

  • Our results showed that the plants of C. procera under both studied environments had intense dynamics throughout the seasons, adjusting morphoanatomical, biochemical, and physiological aspects of their leaves (Figure 2)

  • The present work had as its main goal the investigation of what physiological and anatomical attributes allow C. procera to maintain high performance of photosynthetic metabolism activity even under high vapor pressure deficit (VPD) and low soil water availability

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Summary

Introduction

Changes in global rainfall patterns have resulted in more frequent drought across the semi-arid environments of the world (IPCC Climate Change, 2018). Mainly C3 plants, can be severely damaged and coming under threat of extinction under this scenario when considering the higher frequency of prolonged dry seasons and the low efficiency of water use among these species (Oliveira et al, 2014; Santos et al, 2014). Several plant species present outstanding performance and overcome limited resources, such as low water availability in semi-arid and arid regions, even during prolonged drought (Oliveira et al, 2014). In this context, some species have the ability to colonize environments with different available resources (Tezara et al, 2011; Frosi et al, 2013). Invasiveness can be explained by several functional traits (Funk and Vitousek, 2007; Funk et al, 2016), such as high relative growth rate (Penuelas et al, 2010), increased efficiency in uptake and use of resources, and phenotypic plasticity (Funk and Vitousek, 2007; Davidson et al, 2011)

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