Skip to content
Login Register

#land plants

4 public questions tagged with this topic.

Plant Classification

Embryos retained within maternal tissue are a feature of

Embryophyte name derived by Bower directly refers to retention and nutritional support of diploid embryo within maternal thallus after fertilization. Unlike algal zygote often released free-living and dormant, land plant zygote divides mitotically developing into multicellular embryo inside archegonium venter receiving nutrients via specialized placental transfer cells with labyrinthine walls, ensuring early development protected from drying and UV. Fungi produce dikaryotic mycelium after plasmogamy, cyanobacteria lack embryonic development completely, most algae lack maternal retention. Matrotrophy represents crucial adaptation allowing offspring survival in variable terrestrial conditions.

Ref: Kenrick 2000 Embryophyte embryo evolution; Campbell Ch 29; Bower Archegoniate

View Details
Plant Classification

The earliest land plants appeared approximately

Molecular clocks calibrated with fossils, cryptospore fossils and early macrofossils place earliest embryophytes in mid Ordovician to early Silurian, approximately 470 million years ago, long after Cyanobacteria origin. Evidence includes tetrahedral cryptospore tetrads and dyads with sporopollenin walls from Oman, Argentina and China deposits, plus liverwort-like cuticle fragments and thalloid compressions. Vascular plants appeared later near 430 million years ago. This timeframe predates Devonian forests and far exceeds 100 million years which corresponds to angiosperm radiation. Three point two billion and one billion correspond to prokaryotic and early eukaryotic algal evolution.

Ref: Wellman & Gray 2000 Cryptospores 470 Ma, Nature; Edwards et al. Early land plants

View Details
Plant Classification

The immediate ancestors of land plants are believed to be

Molecular phylogenetics using chloroplast, mitochondrial and nuclear genes, ultrastructure of mitosis, and biochemistry identify Charophyta, freshwater streptophyte algae comprising Charales, Coleochaetales, Klebsormidiales and Zygnematales as closest extant relatives to embryophytes. Charophytes share cellulosic rosette cellulose synthases, phragmoplast-mediated cytokinesis with cell plate, chlorophyll a and b, starch stored inside plastids, and glycolate oxidase photorespiration pathway. Charophyte ancestor underwent terrestrialization approximately 500 million years ago. Chlorophytes diverged earlier, rhodophytes and phaeophytes belong to different supergroups with distinct pigments. This structural framework illustrates phylogenetic relationships and adaptive significance highlighted in competitive examinations focusing on comparative plant morphology and systematics.

Ref: Lewis & McCourt 2004 Charophytes and land plants, Science; Karol et al. 2001

View Details