Summer is the season of watermelon ripening. Cars and ships loaded with watermelon are continuously transported into the city from the place of origin. Interestingly, in long-distance transportation, even if the watermelon is ripe, the seeds will never germinate in the melon. Other plants, such as rapeseed after harvest, have the appropriate temperature and humidity in the pods, and they will sprout out of the pods. Why is that?
Originally, the juice of watermelon fruit contains a large amount of phenolic substances that inhibit seed growth, such as caffeic acid and ferulic acid. They promote the indoleacetate content of plants and catalyze the synthesis of large amounts of indole acetic acid. Indoleacetic acid is a plant growth hormone that promotes cell division and cell elongation and growth. However, its effect is closely related to the concentration, which promotes growth at low concentrations, inhibits growth at high concentrations, and even kills plants.
At the same time, caffeic acid and ferulic acid also interfere with the conversion of energy in plants and the production of ATP, so that the seeds do not get the necessary energy supply during germination, but are in a state of inhibition. Only when the watermelon seeds leave the melons wrapped in the syrup and rinsed with water, the substances that inhibit the germination of the seeds are eliminated, and the seeds are likely to germinate normally. Before the watermelon is planted, the melon farmer usually soaks the seeds with cold water for 4-5 hours and removes the surface mucus, thus increasing the germination rate of the seeds.
In addition to watermelon, most fruits such as melons and tomatoes also have this characteristic.