Photoinhibition of photosynthesis in mature and young leaves of grapevine (Vitis vinifera L.)

Groups of Actinidia deliciosa A. Chev. C.F. Liang et A.R. Ferguson var. deliciosa kiwifruit plants were subjected to soil water shortage (D), while other groups were well irrigated (I). Variations in chlorophyll (Chl) a fluorescence indices and leaf gas exchange were determined once plants were severely stressed (25 d after the beginning of the D-cycle). Daily maximum values of photosynthetic photon flux density (PPFD) were ca. 1 650 μmol(photon) m -2 s -1 , while air temperatures peaked at 34.6 °C. High irradiance per se did not greatly affect the efficiency of photosystem (PS) 2, but predisposed its synergistic reduction by D co-occurrence. Fluorescence showed transient photodamage of PS2 with a complete recovery in the afternoon in both D and I plants. Upon re-watering the efficiency of PS2 was suboptimal (95 %) at day 2 after irrigation was reinitiated. At early morning of the day 5 of re-watering, photosynthesis and stomatal conductance recovered at about 95 and 80 % of I vines, respectively, indicating some after-stress effect on stomatal aperture. Once excessive photons reached PS2, the thermal dissipation of surplus excitation energy was the main strategy to save the photosynthetic apparatus and to optimize carbon fixation. The rather prompt recovery of both Chl a fluorescence indices and net photosynthetic rate during re-watering indicated that kiwifruit photosynthetic apparatus is prepared to cope with temporary water shortage under Mediterranean-type-climates.

Section: Discussionmentioning

confidence: 94%

Response of photosynthetic machinery of field-grown kiwifruit under Mediterranean conditions during drought and re-watering

Montanaro¹,

Dichio²,

Xiloyannis³

2007

“…An increase in F 0 may be induced by the inactivation of part of PS2 RCs (Hong and Xu 1999). In mature grape leaves, when F 0 increased under HI, some PS2 RCs lost their photochemical activity, as indicated by a marked decline in the photochemical efficiency of PS2 (F v /F m ) (Bertamini and Nedunchezhian 2003).…”

Section: Discussionmentioning

confidence: 99%

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

Guo¹,

Guo²,

Zhou³

et al. 2006

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.

“…However, it is also noteworthy that at the drought stage, F 0 of C11/2 leaves increases, whereas other modern genotypes reveal a decrease and WT no response. Elevation in F 0 may result from inhibition of the acceptor side of PSII (Bertamini and Nedunchezhian 2003), Q A reduction, and dissociation of LHCII from PSII (Yamane et al 2000 and references therein). Consequently, F 0 ' of drought-treated C11/2 plants strongly increases.…”

Section: Cf Parameters Responsementioning

confidence: 99%

Are the fluorescence parameters of German chamomile leaves the first indicators of the anthodia yield in drought conditions?

Bączek-Kwinta¹,

Koziel²,

Seidler-Łożykowska³

2011

7-day soil drought followed by 7-day rehydration was applied to potted German chamomile (Chamomilla recutita) plants at the beginning of their generative stage. Plants of a wild type (WT), plus two diploid (2n) and two tetraploid (4n) genotypes were studied, in order to examine the alterations in chlorophyll (Chl) and carotenoids (Car) contents, and chlorophyll fluorescence (CF) parameters during water shortage and rehydration. The fresh mass of the anthodia after the recovery was also studied.WT plants adjust better to water stress than modern breeding genotypes, because drought resulted in the low fall in leaf water content of WT, the lowest decrease in the fresh mass of its anthodia (a 41% decrease from the control), and the most elastic response of the photosynthetic apparatus. 4n C11/2 strain plants suffered from the highest reduction in anthodia yield (87%), and had the lowest constitutive pigment contents. It was also the only genotype which revealed nontypical alterations in various CF parameters obtained on a dark-and light-adapted leaf. During drought, a big increase was noticed in minimal, maximal, and variable fluorescence of PSII reaction centres in the dark-adapted (F 0, F m and F v , respectively), and in the light-adapted state (F 0 ', F m ' and F v '). It was accompanied by the biggest decline in linear electron transport rate (ETR), quantum efficiency of PSII electron transport (Φ PSII ) and photochemical quenching coefficient (q P ). These alterations were prolonged to the stage when the normal leaf water content was retained. On the contrary, C6/2 strain plants had the highest constitutive Chl and Car contents, which additionally increased after rehydration, similarly to the values of F 0 , F m and F v , which reflects the high photosynthetic potential of this genotype. It was accompanied by the relatively high yield of its anthodia after drought. Considering the drop in the yield triggered by drought, it seems to be the only parameter which may be linked with the ploidy level.Although the yield formation of chamomile strains cannot simply be estimated by CF assay, this technique may serve as an additional tool in the selection of plants to drought. The following circumstances should be submitted; namely: measurement at the proper developmental stage of plants, in different water regimes, and an analysis of various CF parameters. The increase in F 0 and F 0 ', and the reduction in ETR, F v '/F m ', Φ PSII and q P values in response to water deficit should be an indicator of the impairment of the photosynthetic apparatus through drought.