Effect of Low Light on Photosynthetic Performance of Tomato Plants-Ailsa Craig and Carotenoid Mutant Tangerine

Abstract

The effects of a five-day treatment with low light intensity on tomato plants-Ailsa Craig and tangerine mutant-at normal and low temperatures and after recovery for three days under control conditions were investigated. The tangerine tomato, which has orange fruits, yellowish young leaves, and pale blossoms, accumulates prolycopene rather than all-trans lycopene. We investigated the impact of low light at normal and low temperatures on the functioning and effectiveness of photosynthetic apparatuses of both plants. The photochemical activities of Photosystem I (PSI) and Photosystem II (PSII) were assessed, and the alterations in PSII antenna size were characterized by evaluating the abundance of PSII-associated proteins Lhcb1, Lhcb2, CP43, and CP47. Alterations in energy distribution and interaction of both photosystems were analyzed using 77K fluorescence. In Aisla Craig plants, an increase in thylakoid membrane fluidity was detected during treatment with low light at a low temperature, while for the tangerine mutant, no significant change was observed. The PSII activity of thylakoids from mutant tangerine was more strongly inhibited by treatment with low light at a low temperature while low light barely affected PSII in Aisla Craig. The obtained data indicated that the observed differences in the responses of photosynthetic apparatuses of Ailsa Craig and tangerine when exposed to low light intensity and suboptimal temperature were mainly related to the differences in sensitivity and antenna complexes of PSII.

Keywords: 77K fluorescence; PSII antenna proteins; electron transport rate; fluidity; low light intensity; low temperature; photosystem I; photosystem II; tangerine mutant; tomato.

Figure 1

Alterations of values for ETR in thylakoid membranes from Ailsa Craig (A) and tangerine (B) plants, treated with low light (LL) and control (NT) or low (LT) temperature for 5 days and after recovery at control conditions for 3 days. Mean values ± SE were calculated from two independent experiments with 3 parallel samples at every time point (n = 6). Significant differences between values at p < 0.05, as estimated by Fisher’s LSD test of multifactor ANOVA analysis, were indicated with different letters.

Figure 2

Alterations in photochemical activity of PSI (A,C) and PSII (B,D) in thylakoid membranes from Ailsa Craig (A,B) and tangerine (C,D) plants, treated with low light (LL) and control (NT) or low (LT) temperature for 5 days, and after recovery at control conditions for 3 days. Results were presented as % from the respective, non-treated control plants (0 days). For PSI, 100% corresponded to 91.5 ± 7.2 and 128.3 ± 3.1 µmol O₂ mg Chl⁻¹ h⁻¹ for Ailsa Craig and tangerine, respectively. For PSII, 100% corresponded to 30.4 ± 1.7 for Ailsa Craig and 48.3 ± 1.8 1 µmol O₂ mg Chl⁻¹ h⁻¹ for tangerine. Mean values ± SE were calculated from two independent experiments with 3 parallel samples at every time point (n = 6). Significant differences between values at p < 0.05 as estimated by Fisher’s LSD test of multifactor ANOVA analysis were indicated with different letters.

Figure 3

Effect of treatment with low light (LL) at control (NT) or low (LT) temperature and after recovery at control conditions on fluorescence ratio F735/F685 (A,C) and F685/F695 (B,D) of Ailsa Craig (A,B) and tangerine (B,D) thylakoid membranes. Mean values ± SE were calculated from two independent experiments with two parallel samples at every time point (n = 4). Significant differences between values at p < 0.05, as estimated by Fisher’s LSD test of multifactor ANOVA analysis, were indicated with different letters.

Figure 4

Fluorescence excitation ratios of emission at 735 nm (E680/E650) (A,C) and at 685 nm (E470/E436) (B,D) in thylakoid membranes from Ailsa Craig (A,B) and tangerine (B,D) plants, treated with low light (LL) at control (NT) or low (LT) temperature and after recovery at control conditions. Mean values ± SE were calculated from two independent experiments with two parallel samples at every time point (n = 4). Significant differences between values at p < 0.05, as estimated by Fisher’s LSD test of multifactor ANOVA analysis, were indicated with different letters.

Figure 5

Degree of fluorescence polarization (P) of the fluorescent probe DPH in thylakoid membranes from Ailsa Craig (A) and tangerine (B) plants, treated with low light (LL) at control (NT) or low (LT) temperature and after recovery at optimal conditions. Mean values ± SE were calculated from two independent experiments with at least 3 parallel samples at every time point (n = 6). Significant differences between values at p < 0.05 were estimated by Fisher’s LSD test of multifactor ANOVA analysis and indicated with different letters.

Figure 6

Abundance of Lhcb1 (A,C) and Lhcb2 (B,D) in thylakoid membranes from Ailsa Craig (A,B) and tangerine (C,D) plants, treated with low light (LL) at control (NT) or low (LT) temperature and after recovery at optimal conditions. Results were presented as % from the respective, non-treated control plants (0 days). Mean values ± SE were calculated from two independent experiments with at least 3 parallel samples at every time point (n = 6). Significant differences between values at p < 0.05 were estimated by Fisher’s LSD test of multifactor ANOVA analysis and indicated with different letters.

Figure 7

Abundance of CP43 (A,C) and CP47 (B,D) in thylakoid membranes from Ailsa Craig (A,B) and tangerine (C,D) plants, treated with low light (LL) at control (NT) or low (LT) temperature and after recovery at optimal conditions. Results were presented as % from the respective, non-treated control plants (0 days). Mean values ± SE were calculated from two independent experiments with at least 3 parallel samples at every time point (n = 6). Significant differences between values at p < 0.05 were estimated by Fisher’s LSD test of multifactor ANOVA analysis and indicated with different letters.