DR KENNETH R. MILLER / SCIENCE PHOTO LIBRARY DR KENNETH R. MILLER / SCIENCE PHOTO LIBRARY
Transmission electron micrograph (TEM) of stacks of grana in a chloroplast from a leaf of maize, Zea mays. The grana in chloroplasts are the sites of photosynthesis in higher plants. They bear the light-receptive green pigment chlorophyll, which contains the enzymes that convert carbon dioxide & water into useful chemical energy in the presence of sunlight. Higher plants usually have 20-50 chloroplasts per cell, or about 500,000 per square millimetre of leaf surface. The black particles in this micrograph are fat droplets which act as a reserve of raw materials for production of new cell membranes. Magnification: x8700 at 35mm size, x61,000 at 8x10-inch size. Reference: MICROCOSMOS, figure 6.13, page 116.
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