Photoinhibition and xanthophyll cycle activity in bayberry (Myrica rubra) leaves induced by high irradiance

Abstract

The effect of high irradiance (HI, photosynthetically active photon flux density of 1 300 μmol m −2 s −1 ) on net photosynthetic rate (P N ), chlorophyll fluorescence parameters, and xanthophyll cycle components were studied in fruit tree bayberry leaves. HI induced the photoinhibition and inactivation of photosystem 2 (PS2) reaction centres (RCs), which was characterized by decreased P N , maximum yield of fluorescence after dark adaptation (F m ), photochemical efficiency of PS2 (F v /F m ) and quantum yield of PS2 (Φ PS2 ), and increased reduction state of Q A (1 -q P ) and non-photochemical quenching (NPQ). Initial fluorescence (F 0 ) showed a decrease after the first 2 h, and subsequently increased from the third hour exposure to HI. Furthermore, a greater increase in the ratio (F i -F 0 )/(F p -F 0 ) which is an expression of the proportion of the Q B non-reducing PS2 centres, whereas a remarked decrease in the slope of F i to F p which represents the rate of Q A reduction was observed in leaves after HI exposure. Additionally, HI caused an increase in the pool size of the xanthophyll cycle pigments and sustained elevated contents of zeaxanthin (Z), antheraxanthin (A), and de-epoxidation state (DES) at the end of the irradiation period. During HI, decreased F m , F v /F m , Φ PS2 , NPQ, slope of F i to F p , V+A+Z, and DES, and increased F 0 , 1 -q P , ratio (F i -F 0 )/(F p -F 0 ), and V were observed in dithiothreitol (DTT)-fed leaves compared to control ones under the same conditions. Hence photoinhibition caused by HI in bayberry was probably attributed to inactivation of PS2 RCs, and photoprotection from photodamage were mainly related to the xanthophyll cycle-dependent heat dissipation in excess photons.

Physiological and growth characteristics of Ginkgo biloba L. exposed to open field and shade enclosure during the reproductive stage

“…In the present study, this parameter was the most representative of the effect of high irradiance stress. Similar observations have also been reported by Guo et al (2006) in bayberry plants subjected to high irradiance.…”

“…According to Guo et al (2006), photoinhibition in higher plants occurs when plants experience irradiance at or above the level that is saturating for growth. The lower photosynthetic rate observed in O-plants could be ascribed to partial photoinhibition.…”

Composition of photosynthetic organisms and diurnal changes of photosynthetic efficiency in algae and moss crusts

“…But for the photosynthetic organisms in BSCs, they have no stomata except for a few liverworts and mosses (Wu 1992). Meanwhile, some studies also reported that the midday depression of photosynthetic efficiency coincided with the higher PAR and photoinhibition (Guo et al 2006;Huang et al 2006). Therefore, we speculate that PAR may play a significant role during the course of diurnal changes of photosynthetic efficiency in BSCs.…”

<b>Morphoanatomy and physiology of Pouteria gardneriana Radlk plantlets grown in vitro at varied photosynthetic photon flux densities

“…Plants grown at low PPFD have low photosynthetic capacity and a low CO 2 assimilation rate. In contrast, an environment with high irradiance can negatively affect photosystem II (PSII) and photosynthesis declines (Guo, Guo, Zhou, Hu, & Shen, 2006).…”