The limiting effect of genome size on xylem vessel diameter is shifted by environmental pressures in seed plants

Abstract Current and previous studies have extensively studied the physiological and ecological consequences of genome size (GS) on plants because of the limiting effect of GS on cell size. However, it is still obscure whether such limiting effect could be shifted by environmental pressures, or not. Here, we compiled a global dataset comprised of GS, xylem vessel diameter (Vdia), xylem hydraulic conductivity (KS), P50 (xylem water potential at the loss of 50% maximum KS), and climate factors of 251 phylogeny and habitat divergent species from 59 families. The results showed that GS could limit the Vdia of the species from the same family sampled in the similar climate conditions. But the expected positive relationship between GS and Vdia became uncertain and even negative across different environmental conditions. Vdia was strongly positively coordinated with mean annual temperature (MAT), mean annual precipitation (MAP), and potential evapotranspiration (PET). Furthermore, Vdia as the anatomic foundation of plant hydraulic performance was strongly positively coordinated with KS and negatively coordinated with −P50. The strong environmental selection on KS and P50 explained the concerted regulation of Vdia by environmental factors. The findings revealed the combined regulation of GS and environmental pressures on xylem cell size and thus affected plant eco‐physiological performance. The shifted cell size limiting effect of GS by environmental factors manifests plants great plasticity under changed environmental conditions.