By the outward appearance of plants, the state of the vital processes of its cells can be determined. For example, if there is not enough water in the cells and the turgor pressure is not enough, then the plant withers (leaves, shoots fall) if the plant does not have enough light, the process of photosynthesis does not take place in it and the plant brightens (chlorophyll on the green set).
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.