Allocation of Absorbed Light Energy in Photosystem II in NPQ Mutants of Arabidopsis.

To analyze changes of energy allocation in PSII at non-steady state photosynthesis, the induction and relaxation of non-photochemical quenching of Chl fluorescence was re-evaluated with the use of Arabidopsis thaliana mutants in which the ability to induce non-photochemical quenching was either enhanced (npq2) or suppressed (npq1 and npq4). When dark-treated leaves of the wild type (WT) were illuminated, very high Φ, which represents the loss of excitation energy via non-regulated dissipation, at the beginning of light illumination was gradually decreased to the steady-state level. In contrast, Φ, representing regulated energy dissipation in PSII, was relatively constant after a significant change in the first 10 min.

Growth Properties and Biomass Production in the Hybrid C4 Crop Sorghum bicolor.

Hybrid vigor (heterosis) has been used as a breeding technique for crop improvement to achieve enhanced biomass production, but the physiological mechanisms underlying heterosis remain poorly understood. In this study, to find a clue to the enhancement of biomass production by heterosis, we systemically evaluated the effect of heterosis on the growth rate and photosynthetic efficiency in sorghum hybrid [Sorghum bicolor (L.) Moench cv.

Physiological functions of PsbS-dependent and PsbS-independent NPQ under naturally fluctuating light conditions.

The PsbS protein plays an important role in dissipating excess light energy as heat in photosystem II (PSII). However, the physiological importance of PsbS under naturally fluctuating light has not been quantitatively estimated. Here we investigated energy allocation in PSII in PsbS-suppressed rice transformants (ΔpsbS) under both naturally fluctuating and constant light conditions.

Light energy allocation at PSII under field light conditions: how much energy is lost in NPQ-associated dissipation?

In the field, plants are exposed to fluctuating light, where photosynthesis occurs under conditions far from a steady state. Excess energy dissipation associated with energy quenching of chlorophyll fluorescence (qE) functions as an efficient photo-protection mechanism in photosystem II. PsbS is an important regulator of qE, especially for the induction phase of qE.

Diurnal and developmental changes in energy allocation of absorbed light at PSII in field-grown rice.

The allocation of absorbed light energy in PSII to electron transport and heat dissipation processes in rice grown under waterlogged conditions was estimated with the lake model of energy transfer. With regard to diurnal changes in energy allocation, the peak of the energy flux to electron transport, J(PSII), occurred in the morning and the peak of the energy flux to heat dissipation associated with non-photochemical quenching of Chl fluorescence, J(NPQ), occurred in the afternoon. With regard to seasonal changes in energy allocation, J(PSII) in the rapidly growing phase was greater than that in the ripening phase, even though the leaves of rice receive less light in the growing phase than in the ripening period in Japan.