Tolerance

The concept of tolerance and its implications can be described as follows:

1. Plants (and other organisms) may have a large tolerance for a certain factor, but

2. plants with a large tolerance for a lot of factors are usually widespread.

3. If a species finds an ecological factor in a suboptimal state, its tolerance against other factors may be drastically reduced. The resistance of graminaceous and many other plants against drought decreases rapidly with soils devoid of nitrogen. This is easy to understand as plants take up a lot of water with dissolved nitrogen compounds under low-nitrogen conditions in order to supply themselves with sufficient nitrogen.

4. As biotic factors play an important role in the presence of plants, many plants live under suboptimal conditions. Often, factors or complexes of factors have a more important role than factors that are more easily recognised. Tropical orchids, for example, can be exposed to full sunlight when kept cold. In nature, they live in shadowy habitats, because they cannot stand the combination of warmth and bright sunlight.

5. The phase of propagation is usually far more sensitive towards limiting factors than the vegetative phase. Flowers, for example, are much more sensitive towards drying out than leaves.