Plant responses to water deficit occur in a complex framework of organ interactions, but few studies focus on the effect of drought stress on all organs in a whole-plant. The effects of repeated dehydration and rehydration (DH) on physiological and biochemical responses in various organs of Periploca sepium Bunge (P. sepium) were investigated. The leaf relative water content decreased significantly during drought, but recovered and showed an increase when compared to well-watered control plants. The malondialdehyde (MDA) content increased in mature and old leaves, but decreased in young leaves, new stems and fine roots during drought, indicating that the young and vigorous tissues of a whole-plant are protected preferentially from the oxidative stress. Among all organs, the fine roots showed the highest levels of proline, total free amino acids (TFAA) and Na+, while the leaves showed the highest levels of total soluble sugars (TSS), soluble proteins (SP), Ca2+ and Mg2+. The response to DH differed in different organs, both in magnitude and in the type of solutes involved. Drought stress increased the contents of proline, TFAA, TSS, SP and K+ in all organs of P. sepium plants, while the accumulation amounts were obviously different among the organs. The storage starch in stems and roots plays an important role in providing carbohydrates for growth. Changes in Na+, Ca2+ and Mg2+ under DH presented a high degree of organ specificity. Our data indicates that response strategies are different between different organs; therefore, evidence the needs to integrate all the information in order to better understand plant tolerance mechanisms.
