PLANT PHYSIOLOGY Chapter Photosynthesis in Higher Plants Chapter Respiration in Plants Chapter Plant Growth and Development M ELVIN C ALVIN born in Minnesota in April, , received his Ph.D. in Chemistry from the University of Minnesota. He served as Professor of Chemistry at the University of California, Berkeley. Just after world war II, when the world was under shock after the Hiroshima-Nagasaki bombings, and seeing the ill- effects of radio-activity, Calvin and co-workers put radio- activity to beneficial use.
He along with J.A. Bassham studied reactions in green plants forming sugar and other substances from raw materials like carbon dioxide, water and minerals by labelling the carbon dioxide with C . Calvin proposed that plants change light energy to chemical energy by transferring an electron in an organised array of pigment molecules and other substances. The mapping of the pathway of carbon assimilation in photosynthesis earned him Nobel Prize in .
The principles of photosynthesis as established by Calvin are, at present, being used in studies on renewable resource for energy and materials and basic studies in solar energy research. Melvin Calvin All animals including human beings depend on plants for their food. Have you ever wondered from where plants get their food? Green plants, in fact, have to make or rather synthesise the food they need and all other organisms depend on them for their needs.
The green plants make or rather synthesise the food they need through photosynthesis and are therefore called autotrophs. You have already learnt that the autotrophic nutrition is found only in plants and all other organisms that depend on the green plants for food are heterotrophs. Green plants carry out ‘photosynthesis’, a physico-chemical process by which they use light energy to drive the synthesis of organic compounds. Ultimately, all living forms on earth depend on sunlight for energy.
The use of energy from sunlight by plants doing photosynthesis is the basis of life on earth. Photosynthesis is important due to two reasons: it is the primary source of all food on earth. It is also responsible for the release of oxygen into the atmosphere by green plants. Have you ever thought what would happen if there were no oxygen to breath?
This chapter focusses on the structure of the photosynthetic machinery and the various reactions that transform light energy into chemical energy.