Fenestration in the leaves of Monstera and its bearing on the morphogenesis and colour patterns of leaves

Programmed Cell Death Remodels Lace Plant Leaf Shape during Development[W]

“…In a vast majority of vascular plants, pinnately or palmately dissected leaves are formed through localized growth enhancement or suppression during the early morphogenetic phase of leaf development (Kaplan, 1984;Sinha, 1999;Dengler and Tsukaya, 2001;Gleissberg, 2002). By contrast, the complex leaf shapes of a handful of monocotyledonous species arise solely through the death of discrete patches of cells early in the leaf expansion phase (Melville and Wrigley, 1969;Kaplan, 1984;Greenberg, 1996;Jones and Dangl, 1996;Beers, 1997;Pennell and Lamb, 1997). In certain Monstera species, the initial pinprick-sized holes formed by PCD are stretched by leaf expansion, and patches formed earlier tear through the leaf margin, forming a deeply lobed leaf (Melville and Wrigley, 1969;Kaplan, 1984).…”

“…By contrast, the complex leaf shapes of a handful of monocotyledonous species arise solely through the death of discrete patches of cells early in the leaf expansion phase (Melville and Wrigley, 1969;Kaplan, 1984;Greenberg, 1996;Jones and Dangl, 1996;Beers, 1997;Pennell and Lamb, 1997). In certain Monstera species, the initial pinprick-sized holes formed by PCD are stretched by leaf expansion, and patches formed earlier tear through the leaf margin, forming a deeply lobed leaf (Melville and Wrigley, 1969;Kaplan, 1984). A single species of the aponogeton family, lace plant, uses PCD during leaf development in quite a different way (Sergueff, 1907): leaf blades retain a simple oblong outline during expansion but become perforated with rectangular holes that are positioned equidistantly between longitudinal and transverse veins.…”

“…What processes from signaling pathways and cell death mechanisms already present in ancestral aponogetons have been coopted for this purpose? Although Monstera and other aroids are more familiar examples of the involvement of PCD during leaf morphogenesis, they are much less tractable than lace plant, because perforations are formed while leaves are rolled tightly in the bud (Melville and Wrigley, 1969;Kaplan, 1984). The accessibility and predictability of leaf perforation formation in the aquatic lace plant provides an attractive model system for the study of developmental PCD in planta.…”

Programmed cell death during plant growth and development

“…While the potential for phagocytosis of apoptotic bodies by plant cells could be explored using protoplast experimental systems, such as that described by Wang et al (1996), heterophagy of wall-bounded plant cells has not been reported. Four fates for plant cells during pcd are presented in Figure 1: (1) complete disappearance of cells, including cell walls (e.g., during aerenchyma formation and the production of fenestrated leaves (Melville and Wrigley, 1968)), (2) crushing, tearing or overgrowth of death cells by their expanding neighbors, as in the case of megaspore development, (3) persistence of cell walls with or without degraded components of dead protoplast (e.g., mature tracheary elements), and (4) post-senescence shedding of entire organs or tissues consisting of dead cells. That autolysis and perhaps autophagy rather than heterophagy appear to be the predominant mechanisms employed during both the suicide and the elimination of plant cells may in part be due to the presence of the plant cell wall.…”

“…These areas then expand along with the growing leaf resulting in a perforated lamina. Although some morphological and physiological aspects of this process have been characterized (Melville and Wrigley, 1968), nothing is known about the molecular biology of this interesting phenomenon. In contrast, more extensive information is available on the biology of cell death programs engaged during germination, vascular differentiation, and stress-and age-dependent death of mature tissues and organs, and these processes are discussed below.…”