They include roots or rootlike structures, a waxy cuticle that covers the surfaces of leaves and stems and limits the evaporation of water, and pores called stomata in leaves and stems that allow gas exchange but close when water is scarce, thus reducing water loss.
词汇讲解：
waxy /'wæksɪ/ adj. 蜡状的
cuticle /'kjʊtɪkl/ n. ‘植物’角皮，角质层;表皮，外皮
scarce /skeəs/ adj. 不足的，稀有的
结构划分：
They include roots or rootlike structures, (a waxy cuticle)(that covers the surfaces of leaves and stems and limits the evaporation of water), and pores (called stomata)(in leaves and stems)(that allow gas exchange but close when water is scarce, thus reducing water loss).
深度分析：
这个句子的主干就是：
They include roots or rootlike structures and pores
修饰一：(a waxy cuticle) ，同位语
中文：一种蜡状角质层
修饰二：(that covers the surfaces of leaves and stems and limits the evaporation of water) ，从句，修饰a waxy cuticle
中文：覆盖在叶子和茎表面并且限制水分蒸发
修饰三：(called stomata) ，修饰pores
中文：称之为气孔
修饰四：(in leaves and stems) ，介词短语
中文：在叶子和茎上
修饰五：(that allow gas exchange but close when water is scarce, thus reducing water loss) ，从句，修饰pores，但是注意这个从句里还有三个修饰成分。
从句：but close
从句：when water is scarce
非谓语动词： thus reducingwater loss
中文：保证气体交换但当水分不足时则会关闭，从而减少水分流失
参考翻译：
他们包括根部或类似根部的结构(一种覆盖在叶子和茎表面并限制水分蒸发的蜡状角质层)以及在叶子和茎上的称之为气孔的毛孔(这些毛孔保证气体交换但当水分不足时则会关闭，从而减少水分流失)。
