TY - JOUR

T1 - Drought differentially elicits antioxidant defense systems in two genotypes of Euphorbia tirucalli

AU - Abuelsoud, Walid

AU - Papenbrock, Jutta

N1 - Funding Information: Egyptian Scientific Missions Department, Egyptian Higher Education Ministry and Leibniz University Hanover co-funded this research. Thanks go also to Dr. Yvana Glasenapp, Hannover, for help in phenolics and flavonoids quantification and profiling by LC?MS.

PY - 2019/10

Y1 - 2019/10

N2 - Euphorbia tirucalli, a member of Euphorbiaceae, is a drought and salt-tolerant species. It is distributed in subtropical and semi-arid parts of Africa and was brought to Asia and North America. The plant has succulent stems performing CAM metabolism and small non-succulent leaves performing C3 metabolism. Different genotypes of E. tirucalli showed different tolerance to drought stress, especially Morocco and Senegal genotypes. This difference has tempted us to investigate the difference in antioxidant stress mechanisms in stems as compared to leaves. Plants from both genotypes have been subjected to drought (10% Volumetric Water Content, VWC) for 8 weeks and the leaves and stems were investigated for their reactive oxygen species (ROS) and antioxidants levels. Shoots of Morocco genotype retained water more efficiently under drought compared to Senegal shoots. Although H2O2 accumulated in stems under drought compared to leaves, however, the stems have elevated levels of various non-enzymatic and enzymatic antioxidants. Stems of Morocco increased their levels of H2O2 more under drought compared to Senegal stems, and Morocco stems showed a higher increase in their non-enzymatic and enzymatic antioxidants under drought. Morocco stems are distinguished by increased ascorbate peroxidase (APX) and peroxidase (POX) activities, while in Senegal stems catalase (CAT) activity specifically increased under drought. Levels of H2O2 in leaves were higher as compared to stems even under control conditions; however, leaves did not show increased antioxidant enzymes levels under drought stress. This tendency to accumulate H2O2 could be used by E. tirucalli as strategy to kill and get rid of leaves under drought to reduce transpirational water loss. These differences in antioxidant systems of Morocco and Senegal genotypes could, at least partly, explain their differences in drought tolerance and may reflect evolutionary adaptations to different local native climates.

AB - Euphorbia tirucalli, a member of Euphorbiaceae, is a drought and salt-tolerant species. It is distributed in subtropical and semi-arid parts of Africa and was brought to Asia and North America. The plant has succulent stems performing CAM metabolism and small non-succulent leaves performing C3 metabolism. Different genotypes of E. tirucalli showed different tolerance to drought stress, especially Morocco and Senegal genotypes. This difference has tempted us to investigate the difference in antioxidant stress mechanisms in stems as compared to leaves. Plants from both genotypes have been subjected to drought (10% Volumetric Water Content, VWC) for 8 weeks and the leaves and stems were investigated for their reactive oxygen species (ROS) and antioxidants levels. Shoots of Morocco genotype retained water more efficiently under drought compared to Senegal shoots. Although H2O2 accumulated in stems under drought compared to leaves, however, the stems have elevated levels of various non-enzymatic and enzymatic antioxidants. Stems of Morocco increased their levels of H2O2 more under drought compared to Senegal stems, and Morocco stems showed a higher increase in their non-enzymatic and enzymatic antioxidants under drought. Morocco stems are distinguished by increased ascorbate peroxidase (APX) and peroxidase (POX) activities, while in Senegal stems catalase (CAT) activity specifically increased under drought. Levels of H2O2 in leaves were higher as compared to stems even under control conditions; however, leaves did not show increased antioxidant enzymes levels under drought stress. This tendency to accumulate H2O2 could be used by E. tirucalli as strategy to kill and get rid of leaves under drought to reduce transpirational water loss. These differences in antioxidant systems of Morocco and Senegal genotypes could, at least partly, explain their differences in drought tolerance and may reflect evolutionary adaptations to different local native climates.

KW - Antioxidants

KW - C3 metabolism

KW - CAM metabolism

KW - Drought tolerance

KW - Lipid peroxidation

KW - Proline

KW - Reactive oxygen species

UR - http://www.scopus.com/inward/record.url?scp=85072077974&partnerID=8YFLogxK

U2 - 10.1016/j.flora.2019.151460

DO - 10.1016/j.flora.2019.151460

M3 - Article

AN - SCOPUS:85072077974

VL - 259

JO - Flora: Morphology, Distribution, Functional Ecology of Plants

JF - Flora: Morphology, Distribution, Functional Ecology of Plants

SN - 0367-2530

M1 - 151460

ER -