Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 1998
Publication Date: N/A
Interpretive Summary: For us, and our crops, minor cuts and scrapes are entry points for disease-causing microorganisms. The wound-healing process of plants is dependent upon the rapid formation of a protective barrier. In many plants this barrier is made of lignin. While lignin is important to plant health, measuring how much is present is a tedious and time consuming task. We have developed a method to rapidly measure the amount of lignin present in plant tissues. Using this method we found several treatments that speed up the formation of lignin by injured plants. Application of one of these treatments increased the resistance of squash to decay. All plants, especially fruits and vegetables, are subjected to injuries which may lead to decay. Our technique will speed research by us and other scientists to devise better methods of promoting plant health. This will ultimately lead to less spoilage of produce in transit, in markets and in our refrigerators.
Lignification of injuries is an important component of a plant's defense against postharvest diseases. Currently available methods for determination of lignin are slow and tedious. We describe a method to rapidly quantify lignin in plant tissue discs based on measurement of color difference following selective staining with Schiff's reagent. The effect of elicitor treatment on accumulation of lignin at 30§C was evaluated using storage tissues of four plants. Root tissues of daikon, turnip and sweet potato all exhibited increased lignification in response to elicitation with pectinase, chitosan or a yeast extract. Acorn squash tissue responded only to pectinase. Squash tissue elicited and then held at 28§C for 18 h developed considerable resistance to infection by Penicillium italicum. Accumulation of lignin over time, by either the color difference method or the thioglycolic acid (TGA) method, were very similar in elicited tissues of the different plants. However, the two methods gave very different impressions of the time course of lignification. As measured by the color difference method, lignin accumulation became apparent only 4 h after elicitation and the lignification process was complete within 24 h. In contrast, lignin accumulation by the TGA method was much slower, increases were not evident until 8 to 12 h after elicitation, and lignin continued to accumulate for 36 more hours