Cover illustration: The inset cover image shows a fully developed aerenchyma in sugarcane root with collapsed cell walls dividing gas spaces. The formation of these intercellular spaces involve cell wall changes and cell death and are important to maintain mechanical strength and structural stability while 40% of the root is gas spaces. The aerenchyma can be used by plants to transport volatile substances as well as oxygen conferring tolerance to flooding. See Leite et al. (pp. 693–708).