
TY  - JOUR
A1  - Munné-Bosch, Sergi 
A1  - Alegre, Leonor 
T1  - The significance of &#946;-carotene, &#945;-tocopherol and the xanthophyll cycle in droughted <emph type="2">Melissa officinalis</emph> plants
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 2000
VL  - 27
IS  - 2
SP  - 139
EP  - 146
KW  - &#945;-tocopherol, antioxidants, carotenoids, drought, photosynthesis, stress, xanthophyll cycle.
UR  - https://doi.org/10.1071/PP99107 
N2  - Diurnal variations in pigment composition, &#945;-tocopherol and photosynthesis were measured during the summer drought and recovery after autumn rainfalls in Melissa officinalis L. grown under Mediterranean climate. Summer drought caused a drastic decrease in relative water content and water potential of leaves to ca 35% and &#8722;3 MPa respectively, indicative of severe stress. Chlorophyll levels decreased progressively in drought, associated with the inability to increase total carotenoids, and especially &szlig;-carotene. In contrast, &#945;-tocopherol increased by ca 60% in response to drought and showed a significant decrease at midday in severely stressed plants. The intrinsic efficiency of PSII photochemistry remained unchanged at predawn throughout the experiment and decreased up to ca 65% in plants exposed to the interaction of high light and drought, associated with an enhanced de-epoxidation state of the xanthophyll cycle. Although droughted M. officinalis plants showed a significant decrease in the endogenous levels of photosynthetic pigments, the antioxidant function of a-tocopherol and the dissipation of excess excitation energy by the xanthophyll cycle may help to avoid irreversible damage to the photosynthetic apparatus. 
ER  -

