Gymnosperms

The origin and early evolution of vascular plant shoots and leaves

“…Polyphyletic leaf origins are reflected in diverse patterns of leaf development among living vascular plants, reviewed by group in: Ambrose, lycophytes [ 114 ]; Tomescu et al ., horsetails [ 75 ]; Schneider and Vasco et al ., ferns [ 111 , 112 ]; Stevenson, gymnosperms [ 115 ]; and Tsukaya, angiosperms [ 116 ]. Shared properties of vascular plant leaf development include initiation in a regular phyllotactic pattern at a distance from stem cells that propagate the shoot axis, establishment of proximodistal, mediolateral and dorsiventral axes of symmetry, vein insertion, laminar development, proliferation and growth, but the sequence and extent to which these events occur and are combined vary, leading to diversity in leaf form [ 105 ].…”

“…However, the extent of homology in developmental traits such as leaf initiation pattern, determinacy, dorsiventrality and lamination is currently unclear. [115]; and Tsukaya, angiosperms [116]. Shared properties of vascular plant leaf development include initiation in a regular phyllotactic pattern at a distance from stem cells that propagate the shoot axis, establishment of proximodistal, mediolateral and dorsiventral axes of symmetry, vein insertion, laminar development, proliferation and growth, but the sequence and extent to which these events occur and are combined vary, leading to diversity in leaf form [105].…”

“…Whisk ferns (figure 2k) have very small bifid leaves subtending sporangia, ophioglossid ferns (figure 2l ) have a single entire leaf, and filmy ferns (figure 2m) have leaves comprising partially webbed bifurcating axes, with lamina a single cell layer thick [112]. Gymnosperm leaves (figure 2n-q) are similarly diverse and range from small and scale-like to large multipinnate forms [115]. ( proliferative) zone of multicellular meristems [121,122].…”