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Ben Gurion University of the Negev (2013)

Photosynthesis and protection from light in annual desert plant species

Eppel, Amir

Titre : Photosynthesis and protection from light in annual desert plant species

Auteur : Eppel, Amir

Université de soutenance : Ben Gurion University of the Negev

Grade : Doctor of Philosophy (PhD) 2013

Résumé partiel
Light is essential for plant growth, since it provides the energy that drives carbon assimilation through photosynthesis. The energy of light, in the visible spectrum, is absorbed by light harvesting protein-pigment complexes that are found in the chloroplasts of plants. The energy absorbed is funneled to drive the primary reaction that converts the energy of light into chemical energy, which occurs at photosystem II (PSII) reaction centers. As a byproduct of this reaction, there is continuously occurring photodamage to the PSII reaction centers, which requires constant repair ; if the rate of damage creation exceeds the rate of repair, it leads to long-term damage to PSII, which is termed photoinhibition. Environmental stresses, such as drought, increase the risk of photoinhibition in plants. In order to avoid photoinhibition, plants possess various mechanisms to reduce the damage in PSII. Photoprotective mechanisms can be divided into two forms : mechanisms that reduce the amount of light that is absorbed by the light harvesting complexes and mechanisms that mitigate the potentially damaging energy after it has been absorbed by the light harvesting complexes. One of the mechanisms that reduce light absorbance is the accumulation of non-photosynthetic pigments, such anthocyanin. Two important mechanisms that deal with energy after it has been absorbed by PSII are nonphotochemical quenching (NPQ), and photorespiration. NPQ diverts energy directly and harmlessly into heat. Photorespiration is another process that protects PSII from photoinhibition in an oxygen-dependent manner. Annual desert plants are exposed to high light intensity that can cause photodamage, especially when photosynthesis is inhibited due to unfavorable environmental conditions, such as drought and a high vapor pressure deficit. On the other hand, annual plants need to complete their life cycle in a relatively short period of time, before water is lost from the soil due to the high evaporation that occurs in deserts. The goal of this research was to study how photoprotective mechanisms are used by annual desert plants, under various conditions. In order to address this goal, two different studies were performed.

Mots clés : Desert plants — Adaptation — Israel — Negev ; Annuals (Plants) — Environmental aspects — Israel — Negev ; Photosynthesis — Environmental aspects

Présentation (BGU)

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Page publiée le 31 mars 2015, mise à jour le 21 novembre 2018