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For example, chloroplasts in plants and green algae have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but instead contain stroma and grana thylakoids. The glaucocystophycean plastid—in contrast to chloroplasts and rhodoplasts—is still surrounded by the remains of the ...
Chloroplasts probably evolved following an endosymbiotic event between an ancestral, photosynthetic cyanobacterium and an early eukaryotic phagotroph. [17] This event (termed primary endosymbiosis) is at the origin of the red and green algae (including the land plants or Embryophytes which emerged within them) and the glaucophytes, which together make up the oldest evolutionary lineages of ...
A plant cell which contains chloroplasts is known as a chlorenchyma cell. A typical chlorenchyma cell of a land plant contains about 10 to 100 chloroplasts. In some plants such as cacti, chloroplasts are found in the stems, [186] though in most plants, chloroplasts are concentrated in the leaves. One square millimeter of leaf tissue can contain ...
The red algae are pigmented with chlorophyll a and phycobiliproteins, like most cyanobacteria, and accumulate starch outside the chloroplasts. The green algae and land plants – together known as Viridiplantae (Latin for "green plants") or Chloroplastida – are pigmented with chlorophylls a and b, but lack phycobiliproteins, and starch is ...
The life cycle of a dioecious flowering plant (angiosperm), the willow, has been outlined in some detail in an earlier section (A complex life cycle). The life cycle of a gymnosperm is similar. However, flowering plants have in addition a phenomenon called ' double fertilization '.
Chloroplasts and mitochondria also replicate semi-autonomously outside of the cell cycle replication system via binary fission. [12] Consistent with the theory, decreased genome size within the organelle and gene integration into the nucleus occurred. Chloroplasts genomes encode 50-200 proteins, compared to the thousands in cyanobacterium. [13]
The Zygnematophyceae, formerly known as the Conjugatophyceae, generally possess two fairly elaborate chloroplasts in each cell, rather than many discoid ones. They reproduce asexually by the development of a septum between the two cell-halves or semi-cells (in unicellular forms, each daughter-cell develops the other semi-cell afresh) and sexually by conjugation, or the fusion of the entire ...
Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores.