Use of this pattern in the detection of smog-forming hydrocarbons in car exhaust gases

Diagnosis of damage to vegetation is made on the basis of a syndrome which includes three types of symptoms. Macroscopically, silvering, glazing, streaking, and a formation of anthocyanin is observed. Microscopically, cell engorgement is followed by cellular dehydration in the region of the substomatal chamber. In addition there is an orientation of damage on the leaf producing a pattern which is related to the differential maturity of leaf cells. This pattern was first observed in the field and is always observed when smog damage occurs in the Los Angeles area. Older terminology described it as damage to newly matured leaves. More careful observation following smog periods of a single day showed a definite pattern which was related to the state of maturity of that portion of the leaf where injury was observed. Consecutive days of smog produce separate bands of injury on rapidly growing plants. In many cases, only a narrow transverse band of cells is very sensitive at one time. On a given leaf or blade, older bands of damage are found nearer the leaf tip and more recent damage nearer the base. No such precise pattern of damage has been previously noted, although a vague type of patternmore » has been reported in describing damage caused by hydrogen sulfide and sulfur dioxide and has been observed from ozone. This pattern first observed in the Los Angeles area is produced under controlled conditions by the oxidation products of gasoline and ozone; gasoline, ozone and oxides of nitrogen; and most readily by car exhaust gases and ozone.« less