BIOLOGY 3 Lecture Notes - Lecture 12: Infant Mortality, Panicum, Stoma
Document Summary
Less than one half of one percent of the earth"s atmosphere is comprised of carbon dioxide. The oxygen that is released into the atmosphere comes from the split water molecule, not from splitting co2. And plants need more than water, co2 and sunlight. All the wood (cellulose) on the planet is the result of fixed carbon dioxide. Atmospheric co2 has varied considerably during earth"s history. The energy of ancient sunshine, plus ancient atmospheric carbon dioxide, was locked up in plant cellulose which when buried and compressed became coal. Organisms that can breakdown cellulose did not evolve until after the carboniferous which allowed plant material to accumulate. Today cellulose is turned back into co2 by wood digesting insects and fungi. Photosynthetic organisms sequester the tiny amount of co2 that is in the atmosphere because they have an enzyme with a high affinity for co2 . Co2 enters the plant primarily through the leaves and rarely the stems.
