Three species, Zygophyllum coccineum L., Zygophyllum decumbens
Delile and Zygophyllum simplex L., (Zygophyllaceae) were collected
from three localities of Wadi Hagul in Egypt to study their adaptive
responses to different environmental conditions. Plant analyses (degree of
succulence, water content, total pigments, proline, antioxidant enzymes,
total phenols, ascorbic acid, hydrogen peroxide and malondialdehyde)
were estimated to study their roles in the adaptive responses of those
plants under their natural drought conditions. Results have revealed that
xerophytes can further be divided into two groups depending on their
drought tolerance strategies. The first group includes perennial plants
(Zygophyllum coccineum and Zygophyllum decembens) that able to
tolerate and resurrect following desiccation into photosynthetically active
states in a short period of time, the other is the dessication avoiding
group; annual or biennial plant (Zygophyllum simplex), which possess an
improved water-storing organ, efficient water conduction within the plant
body and/or a combination of these features. Moreover, plants in this
group (true xerophytes) are thought to have a unique system to cope with
stress tolerance, since they are able to defend their photosynthetic
apparatus and other fragile cellular components from composite stresses
in the harsh environments in which they are found.