factors such as aba, ga3, ph and ca2+; and the specific levels of aqps in certain parts of the plant, such as roots or leaves, helps to draw as much water into the plant as possible. by understanding the mechanisms of both aqps and the hormone aba, scientists will be better able to produce drought-resistant plants in the future. it is interesting that plants that are consistently exposed to drought have been found to form a sort of "memory". a study by tombesi et al., found that plants which had previously been exposed to drought were able to come up with a sort of strategy to minimize water loss and decrease water use. they found that plants which were exposed to drought conditions actually changed the way they regulated their stomata and what they called "hydraulic safety margin" so as to decrease the vulnerability of the plant. by changing the regulation of stomata and subsequently the transpiration, plants were able to function better when less water was available. in animals for animals, the most stressful of all the abiotic stressors is heat. this is because many species are unable to regulate their internal body temperature. even in the species that are able to regulate their own temperature, it is not always a completely accurate system. temperature determines metabolic rates, heart rates, and other very important factors within the bodies of animals, so an extreme temperature change can easily distress the animal's body. animals can respond to extreme heat, for example, through natural heat acclimation or by burrowing into the ground to find a cooler space. it is also possible to see in animals that a high genetic diversity is beneficial in providing resiliency against harsh abiotic stressors. this acts as a sort of stock room when a species is plagued by the perils of natural selection. a variety of galling insects are among the most specialized and diverse herbivores on the planet, and their extensive protections against abiotic stress factors have helped the insect in gaining that position of honor. in endangered species biodiversity is determined by many things, and one of them is abiotic stress. if an environment is highly stressful, biodiversity tends to be low. if abiotic stress does not have a strong presence in an area, the biodiversity will be much higher. this idea leads into the understanding of how abiotic stress and endangered species are related. it has been observed through a variety of environments that as the level of abiotic stress increases, the number of species decreases. this means that species are more likely to become population threatened, endangered, and even extinct, when and where abiotic stress is especially harsh.