The volume of flame, however, is increased by inert gas, and there is a proportionate diminution of the heating effect. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 Various. Nitrogen by itself is an inert gas, colorless and uninflammable. Scientific American Supplement No. 819 Various.
Tomato Spotted Wilt Virus. The tomato spotted wilt virus (TSWV) causes dark brown, purple or black spots on leaves. The spots can spread to the stems, causing cankers and streaks. The foliage begins to wilt once the disease spreads, and the leaves become stiff.
The appearance of yellow leaves on your tomato plant is usually not a death sentence. However, it does mean that your plant has a problem in need of attention and correction. Tomatoes need nitrogen; their leaves will turn yellow without it. Mix some compost or used coffee grounds in with the soil to determine if a lack of nitrogen is the problem. If the bottom leaves of your tomato plant turn yellow, it's probably lacking in important nutrients. It may not be getting adequate sunlight.