Fungi cannot grow in dark .why?
Answers
Answer:
Explanation:
The study of plant disease, plant pathology, is a large and important one. Many universities have entire departments of plant pathology. The importance of the subject is obvious; since the beginning of agriculture humans have had to endure major crop losses because of disease. Even today, when crop health is under careful scrutiny, disease may suddenly strike and ruin an entire season's growth. It happens every year in some part of the globe, even in so-called developed nations.
Most plant diseases are caused by fungi; losses to bacteria and viruses are important, but less so than those caused by fungi. A great diversity of fungi cause plant disease, nearly all major groups are involved. In spite of these numbers there are just two types of parasite to consider: nectrotrophs and biotrophs. Necrotrophs are a little like predators; they kill the tissues they are about to consume before they eat them. Unlike predators, however, they don't normally kill the whole organism, just a part of it. They do this by means of toxins that diffuse out into the host tissues, killing the cells they encounter. The fungus then extends its hyphae into these killed areas and digests them. Biotrophs obtain their nutrition from living cells with which they may establish fairly long-lived associations. They usually penetrate the cell walls of their hosts and establish contact with the cell membrane by means of haustoria, cells specialized for the absorption of nutrients.
Plants do not just accept parasitic fungi. They have a large array of defense mechanisms that guard against fungal disease so that most fungi cannot get in. These defenses include physical barriers like the tough cuticle lining the surfaces of plants or the bark on trees. Chemical barriers including various toxins and strong oxidizers may be utilized. Fungi in their turn have developed ways of circumventing these defenses and seem to be able to develop new ones as soon as the plant confronts them. Some scientists have referred to this as a biological arms race. Plants differ greatly from one another in how they resist disease.
NECROTROPHS