Chapter 1

Introduction to Plants and Botany

Topics

• Why knowledge in Botany is crucial?

• What is a plant?

• Kingdom Plantae

• Origin of photosynthesis

• Origin of plants

Why Botany? Me, others and abiotic environment

• Buildup of atmospheric CO2 - many sources - global climate change/warming

• CO2 removal and O2 release - only one way - Can plants reverse the CO2 accumulation? - plants have changed earth’s climate - impacted evolution and biodiversity

• Plants & People: Food - agriculture and human society today; Fiber - keep us unnaked; Lumber and paper - forestry and wood-based industries; Chemicals - Phytopharmacognosy, Dyes, Flavors, Perfumes, Pesticides, Preservatives, Texture-makers, Hormones; Biotechnology; Beauty and Spirituality

http://www.botanic.cam.ac.uk/Botanic/Trail.aspx?p=27&ix=11

Plants – Kingdom Plantae

Defining the term, plant, is difficult

– Inclusion or exclusion of some groups

– Green algae - similar biochemistry

– Archaeplastids – plants+green and red

algae

– phytoplanktons – CaCO3

tests – global CO2-O2

balance

• Brown algae: Is it a plant?

Plant Systematics - Natural selection

• Organisms make non-identical offspring whose features pass to its offspring

• Offspring with features that are well-adapted to the environment reproduce more

• New phenotypes arise periodically

by mutations - P=G X E• Natural selection - new features are

eliminated or continued/balanced• Evolution by natural selection is

consistent with:– observations on nature/life

– experimentation

– chemistry and physics

Origin of photosynthesis and plants

• Life on earth ~3.5 bybp with prokaryotes (bacteria and later archaeans)– Photosynthesis - 2.8 bybp in cyanobacteria mainly

• Organelles by endosymbiotic events (1.5 bybp) followed by division of labor and specialization– Eukaryotes nuclei and other organelles (plants, fungi, animals,

algae)

– DNA became stationary in its own organelles

– Those with mitochondria evolved to be protozoans, fungi, and animals

– Those with mitochondria + chloroplasts evolved into plants and algae – plants evolved from green algae ~475 mybp

Photosynthetic bacteria•Cyanobacteria – oxygenic - water is e donor - make O2

•Purple and purple sulfer bacteria, green sufer and green gliding bacteria etc. - nonoxygenic - H2S is a main e donor

Chl a + c/d + carotenoids

Chl a + b + carotenoids

Archaeplastid super group

Origin of plants

• Green algae to Bryophytes (~475 mybp) to Tracheophytes

• Flowering plants evolved 100-120 mybp– Many characteristics evolved with/following the flower

• Fruits• Simple, flat, broad leaves• Complex vascular syst.• Wood• Most dominant today

• Cladogram NEXT