Effects of low irradiation on photosynthesis and antioxidant enzyme activities in cucumber during ripening stage

Abstract

In order to investigate the effects of low irradiation (LI) on cucumber (Cucumis sativus L. cv. Jinyou 35) during a ripening stage, an experiment was conducted in a climate chamber. Two levels of PAR were set for plants: normal irradiation [NI, 600 μmol(photon) m -2 s -1 ] and LI [100 μmol(photon) m -2 s -1 ], respectively. The experiments lasted for 9 d; then both groups of plants were transferred under NI [600 μmol(photon)m -2 s -1 ] to recover for 16 d. The plants showed severe chlorosis after the LI treatment. Chlorophyll (Chl) a, initial slope, photosynthetic rate at saturating irradiation (P max ), light saturation point, maximal photochemical efficiency of PSII (F v /F m ), electron transport rate of PSII (ETR), soluble protein content, and catalase (CAT) activity in cucumber leaves decreased under LI stress, while Chl b, carotenoids, light compensation point, nonphotochemical quenching (q N ), superoxide dismutase (SOD), and malondialdehyde (MDA) exhibited an increasing trend under LI. After 16 d of recovery, values of P max , F v /F m , ETR, q N , SOD, CAT, MDA, and soluble protein were close to those of the control after one, three, and five days of the LI treatment, while those kept under LI for 7 and 9 d could not return to the control level. Therefore, 7 d of LI stress was a meteorological disaster index for LI in cucumber at the fruit stage.Additional key words: lipid peroxidation; low light intensity; meteorological disaster; PN/PPFD response curve.

Low temperature and low irradiation induced irreversible damage of strawberry seedlings

“…In our study, compared to the control, the value of F0 under LI stress was higher and restored to the control level after 15 d of recovery (Fig. 3D), implying that low light intensity induced reversible inactivation of PSII reaction center, which was consistent with the results of Yang et al (2016). Whereas, the large decline in Fm and Fv (both were unrecoverable) demonstrated that LL caused the destruction of PSII reaction center (Fig.…”

“…For example, stomatal closure following chilling may be a direct low-temperature effect on the function of guard cells, or an indirect response to an increase of intercellular CO2 concentration (Ci) caused by a chill-induced loss of Rubisco activity. Yang et al (2016) studies show that low irradiation (LI) may block the transport of electrons in the photosystems, reduce the activity of carbon assimilation enzymes, and alter the activity of antioxidant enzymes. Therefore, low temperature and low light intensity can affect the performance and activity of photosynthetic apparatus.…”

Conjugated Polymer Nanoparticles to Augment Photosynthesis of Chloroplasts

“…Thee xperiments were conducted with the optimal CPNs concentration (10 mgmL À1 )a nd light intensity (4 mW cm À2 ), which is 30 %o ft he light saturation for photosynthesis (Supporting Information, Figure S2). [15] As shown in Figure 3c,under light irradiation, the absorbance at 600 nm gradually decreases with prolonged irradiation time, which implies that the photosynthesis of chloroplasts themselves leads to DCPIP reduction. Fort he chloroplast/CPN complex, the reduction rate of DCPIP is obviously accelerated in comparison to chloroplast itself.C PNs could not reduce DCPIP without chloroplasts,demonstrating the accelerated reduction rate of DCPIP is attributed to the combination of chloroplast and PFP-NPs.B yb inding to the membrane of chloroplasts,PFP-NPs with good light-harvesting ability strongly absorb ultraviolet light and transform to blue light that could be absorbed by chloroplasts,t hereby enhancing the sunlight utilization of chloroplasts.A saconsequence,C PNs endow the chloroplast/PFP-NP system with better solar energy conversion than natural chloroplast.…”

Conjugated Polymer Nanoparticles to Augment Photosynthesis of Chloroplasts

“…Considering blue light is involved in a broad range of plant processes and associated with the expression of sun‐type characteristics such as a high photosynthetic capacity at the chloroplast level, blue‐emitting PFP‐NPs were firstly investigated. The experiments were conducted with the optimal CPNs concentration (10 μg mL −1 ) and light intensity (4 mW cm −2 ), which is 30 % of the light saturation for photosynthesis (Supporting Information, Figure S2) . As shown in Figure c, under light irradiation, the absorbance at 600 nm gradually decreases with prolonged irradiation time, which implies that the photosynthesis of chloroplasts themselves leads to DCPIP reduction.…”