A flower of the same GFP plant as in the last image. While the natural color of chlorophyll is green, which is the cause of the green color of plants, its fluorescence is red. Therefore the green leaves of a flower of an Arabidopsis plant are red in this image and the white petals are transparent, because they do not have a natural fluorescence.
Pumpkin, squash and other species from the cucurbit family contain the largest sieve elements known and have been the subject of phloem investigations for more than a century. Two adjacent sieve elements with sieve plates are shown here.
A fluorescence micrograph of a cross section through a bamboo stem. Phloem, the system plants use to move nutrients, is the bright blue/white area. Sieve elements, the tubes used to transport sugar through the phloem, are the darker circles within the phloem.
Plants are not defenseless, they have mechanisms called forisomes to counteract attacks. An injured sieve element (in green) is shown here. The large red body in the center is a forisome.
Scanning electron microscopy permits imaging of surfaces at high resolution. Objects as small as 1 nanometer (one billionth of a meter) can be resolved. A sieve plate with sieve plate pores is shown above. Nutrients must pass through these tiny openings as they travel through a plant.
Green Fluorescent Protein (GFP) is a protein from a deep sea jellyfish which fluoresces in green when excited with blue light. This protein has become one of the most important proteins in cell biology. A root that carries a phloem protein fused to GFP is shown here.
Starch grains in a storage cell. Starch is the storage form of sugars in plants and the most important substance in human nutrition. Potatoes, rice, wheat (flour) and many other important food sources are mainly comprised of starch.
A microscopic image of a cross section through a leaf. In plants, photosynthesis takes place in leaves. Photosynthesis uses energy from the sun to convert carbon dioxide and water into sugars. The energy stored inside the sugars is the basis for almost all life on earth.
This is the first image of living translocating sieve elements taken with a confocal laser scanning microscope. The picture was a cover image of the journal “Plant Cell” in 1998.
Forisomes are unique in that they contract in response to calcium ions or pH changes. They can even be excited electrically. Because of their unique properties, forisomes are currently the subject of investigations to assess the feasibility of using them for flow control in microchips or to block tumor arteries.
Aphids are among the animals that directly feed on sieve elements. Because aphids cannot see the sieve elements, they probe cell sap on their way through the tissue until they “taste” the right solution.
Aphids can spread out quickly because they have an extremely high reproductive rate. Adults carry their already developed children, which in turn carry developing grandchildren. They also can grow wings to spread out and infest new plants.
An electron micrograph of a cross section through a plant cell wall. The cell wall is layered and thick to withstand mechanical forces. Cell walls like this form a substance we usually call wood. A major part of cell walls are sugars.
A fluorescence micrograph of an Arabidopsis thaliana root. The phloem is loaded with a dye that fluoresces in blue.
