Plant Origins & Adaptations Lecture 21 PDF
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Uploaded by AdventuresomeMridangam
University of Maryland, College Park
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Summary
This lecture focuses on plant origins, specifically relating modern plants to green algae and discussing the transition to land. It details adaptations like the development of vascular tissues, seeds, and the evolution of flowers. The summary also covers plant reproduction strategies.
Full Transcript
Plant Origins closest relative to modern plants = green algae (Charophytes) Charopyceans = closest relative to land plants ○ Same proteins in plasma membranes for synthesizing cellulose ○ Share anti-photorespiration enzymes in organelles called peroxisomes ○ Similar structure with agellated sperm ○...
Plant Origins closest relative to modern plants = green algae (Charophytes) Charopyceans = closest relative to land plants ○ Same proteins in plasma membranes for synthesizing cellulose ○ Share anti-photorespiration enzymes in organelles called peroxisomes ○ Similar structure with agellated sperm ○ Similar microtubules during cell division Life in water is easy Bathed in nutrients Support against gravity = buoyancy Extensive transport not necessary Gametes, offspring dispersed by water No problem of desiccation Leave Water more direct sunlight Nutrients and minerals on land Abundant CO2 for photosynthesis Absence of herbivores New niches available Land is harsh Land plants must ○ Conserve water - cuticle ○ Transport nutrients ○ Withstand gravity ○ Disperse gametes ○ Protect vulnerable life stages ◆ Sporopollenin fl 4 successful adaptive radiations of plants 1. Non-vascular (bryophytes), moss 2. Pteridophytes (ferns) 3. Gymnosperms (Pine) 4. Angiosperms Non-vascular plants moss Abundant 2 major breakthroughs ○ Cuticle ○ Protected embryo Limited by ○ Lack of vascular tissue and support ○ Reliance on water for reproduction ○ Lack of a durable dispersal phase Ferns ( rst vascular plant) seedless vascular plants Breakthrough ○ Vascular tissue = tracheids ◆ Large size - lignin ◆ Ef cient distribution of water and nutrients by xylem and phloem Overtopping ○ Competition for light Limited by presence of fragile gametophyte stage Reliance on water for reproduction Gymnosperms Naked seed = no ovaries for development of seeds Breakthroughs fi seed plants fi ○ Evolution of seeds ◆ Embryo protected inside seed ◆ Packed with food supply ◆ Wait favorable conditions ◆ Carried by wind or animals ○ reduction of gametophyte ◆ Male gametophyte can be carried by wind to female gametophyte ◆ Heterospory Limited ○ Wind pollination = inef cient, must produce a lot of pollen Angiosperms owering plant Most successful More ef cient pollination ○ Don’t need to rely on wind ○ Easier to avoid inbreeding Flowers and fruits are costly to produce fi fi Fruits derived from ovary of the ower fl fl ○ Reproduce even in low abundance
