Submicroscopic, infectious agent, too small to be seen with a compound microscope, that multiplies only in living cells. A virus consists of nucleic acid (DNA or RNA) surrounded by a protein coat.
Virus particles can be rod shaped, like TMV on the left or isometric (spherical) as on the right.
Teresa Sawyer, Electron Microscope Facility. Images taken with the Titan ChemiStem made by FEI CO in Hillsboro OR.
Lack of freshness and turgor and drooping of leaves from lack of water; a vascular disease that interrupts the plant's normal uptake and distribution of water.
The plant on the left is wilting due to Verticillium wilt, while plant on right has leaf spot and stem rot.
The yellow color of plant parts resulting from the excessive proportion of yellow pigments, in turn produced by the underdevelopment or partial destruction of the green pigments.
