The Structure and Function of Xylem in Seed- Free Vascular Plants: An Evolutionary Perspective
نویسنده
چکیده
The evolution of xylem was critical to the success of embryophytic land plants. According to the fossil record, the earliest terrestrial autotrophs were algae followed by bryophytes, simple organisms that lacked the ability to effi ciently transport water (Raven 1984 ; Sperry 2003 ; Taylor et al. 2009 ; Pittermann 2010 ). Like their ancestors, today’s non-vascular plants have essentially two options for survival: inhabit perennially wet substrates such as stream sides or exploit poikilohydry, the capacity to recover from near complete desiccation (Niklas 2000 ; Proctor and Tuba 2002 ; Sperry 2003 ). In the absence of xylem, non-vascular plants are subject to the vagaries of
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