Changes in carotenoids, tocopherols and diterpenes during drought and recovery, and the biological significance of chlorophyll loss in Rosmarinus officinalis plants

Abstract

Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) alpha-tocopherol increased 9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and beta-carotene contents decreased on a dry-weight basis, but an 80% increase in lutein and constant levels of beta-carotene were observed on a chlorophyll basis; (iii) there were transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status, alpha-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, alpha-tocopherol and abietane diterpenes to chlorophyll increase.

Growth Characteristics, Physiological and Metabolic Responses of Teak (Tectona Grandis Linn. f.) Clones Differing in Rejuvenation Capacity Subjected to Drought Stress

“…In addition to structural roles, they are well known for their antioxidant activity by quenching 3 Chl and 1 O 2 , inhibiting lipid peroxidation, and stabilizing membranes (DEMMIG-ADAMS and ADAMS, 1992;FRANK and COGDELL, 1996;NIYOGI, 1999). Carotenoids also play a critical role in the assembly of the light-harvesting complex and in the radiationless dissipation of excess energy (STREB et al, 1998;MUNNÉ-BOSCH and ALEGRE, 2000).…”

Does a terminal drought tolerance QTL contribute to differences in ROS scavenging enzymes and photosynthetic pigments in pearl millet exposed to drought?

“…Stress caused a significant decline in total chlorophyll and carotenoids content in the magnitude usually described as "non-lethal" (roughly 10-30%) under harsh drought stress in pearl millet (Ashraf et al, 2001) and other species (Terzi and Kadioglu, 2006;Kiani et al, 2008;Farooq et al, 2009). In certain species like rosemary and maize retaining of carotenoids level and so decrease of Chl/Car ratio due to drought conditions was reported (MunneÂ-Bosch and Alegre, 2000;Mohammadkhani and Heidari, 2007). In contrast to these results we found an increased Chl/Car ratio suggesting proportionally higher loss of carotenoids compared to chlorophylls and therefore the involvement of other strong ROS scavenging mechanisms additional to carotenoids.…”

“…Many reports emphasize the role of carotenoids (especially xanthophylls) in direct deactivation of ROS in homoiochlorophyllous plants (e.g. Demmig-Adams and Adams, 1992;MunneÂ-Bosch and Alegre, 2000;Takano et al, 2005;Telfer, 2005;Farooq et al, 2009). Xanthophylls were shown to be spatially associated with chlorophylls (Schmid, 2008) where they can account up to 50% of total carotenoids content and contribute sustaining the photochemical functions (Demmig-Adams and Adams, 1992;Farooq et al, 2009).…”

Preparation of phytol-loaded nanoemulsion and screening for antioxidant capacity

“…There are a number of commercially used natural antioxidants, including some diterpenes-kahweol, cafestol [44], carnosic acid, and carnosol [19], and oxidation products of carnosic acid (rosmanol and isorosmanol) [45]. On the other hand, there are also numerous natural antioxidants with reactive hydroxyl (-OH) groups, including carvacrol, thymol, euginol, isoeuginol, gereniol, caffeic acid, p-cumaric acid, terpein-4-ol, alpha-terpenol, limonen, and p-cymene [46].…”