Effects of Nitrogen Deficiency on Gas Exchange, Chlorophyll Fluorescence, and Antioxidant Enzymes in Leaves of Rice Plants

Abstract

Gas exchange, chlorophyll (Chl) fluorescence, and contents of photosynthetic pigments, soluble proteins (ribulose-1,5bisphosphate carboxylase/oxygenase, RuBPCO), and antioxidant enzymes were characterized in the fully expanded 6 th leaves in rice seedlings grown on either complete (CK) or on nitrogen-deficient nutrient (N-deficiency) solutions during a 20-chase period. Compared with the control plants, the lower photosynthetic capacity at saturation irradiance (P max ) was accompanied by an increase in intercellular CO 2 concentration (C i ), indicating that in N-deficient plants the decline in P max was not due to stomatal limitation but due to the reduced carboxylation efficiency. The fluorescence parameters Φ PS2 , F v ′/F m ′, electron transport rate (ETR), and q P showed the same tendency as P max in N-deficient plants. Correspondingly, a higher q N paralleled the rise of the ratio of carotenoid (Car) to Chl contents. However, F v /F m was still diminished, suggesting that photoinhibition did occur in the photosystem 2 (PS2) reaction centres. In addition, the activities of antioxidant enzymes on a fresh mass basis were gradually lowered, leading to the aggravation of membrane lipid peroxidation with the proceeding N-deficiency. The accumulation of malonyldialdehyde resulted in the lessening of Chl and soluble protein content. Analyses of regression showed PS2 excitation pressure (1 -q P ) was linearly correlated with the content of Chl and inversely with soluble protein (particularly RuBPCO) content. There was a lag phase in the increase of PS2 excitation pressure compared to the decrease of RuBPCO content. Therefore, the increased excitation pressure under N-deficiency is probably the result of saturation of the electron transport chain due to the limitation of the use of reductants by the Calvin cycle. Rice plants responded to N-deficiency and high irradiance by decreasing light-harvesting capacity and by increasing thermal dissipation of absorbed energy.

β-Carotene production enhancement by UV-A radiation in Dunaliella bardawil cultivated in laboratory reactors

“…Furthermore, N deficiency can produce oxidative damage in illuminated cultures as reported for higher plants (38). Thus, carotenoid accumulation might be a biological response to induce oxidative damage.…”

“…It was shown that nitrogen deficiency affected the photosynthetic apparatus in leaves of rice plants, leading to lowered fluorescence parameters (photosynthetic yield, quantum yield for photosystem II, PSII, electron transport rate, and quenching) as well as lowered photosynthetic capacity at saturation irradiance, which are indicators of photoinhibition. In addition, the carotenoid-to-chlorophyll ratio increased and the activities of antioxidant enzymes were lowered, which led to aggravation of membrane lipid peroxidation (i.e., oxidative damage) (38).…”

“…In N-deprived mulberry (Morus alba) plants, lipid peroxidation and activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase increased (24), while in rice (Oryza sativa) plant leaves, changes in the level of antioxidant enzyme activities were found (25). This suggests that a combination of UV-A and N starvation could be a tool for enhancing carotenoid production in microalgae.…”

Chlorophyll a fluorescence as a tool to monitor physiological status of plants under abiotic stress conditions

“…Nitrogen is also an important element in RuBisCO photosynthetic complexes, the Calvin-Benson cycle enzymes, chlorophyll, and carotenoids (Correia et al 2005). Nitrogen deficiency contributes to reductions in transpiration, stomatal conductance, the chlorophyll and carotenoids content, and the concentration of soluble sugars (Huang et al 2004). Insufficient nitrogen uptake also reduces the electron acceptor pool in PSII and decreases RuBisCO and phosphoenolpyruvate carboxylase (PEPCase) activity (Correia et al 2005).…”

Local wind monitoring matched with lichen Pseudevernia furfuracea (L.) Zopf transplantation technique to assess the environmental impact of a biomass power plant

“…Lipid peroxidation was measured according to the experimental procedure of Huang et al (2004). First, 50 mg of thalli was rinsed in distilled water and homogenized in 0.1% trichloroacetic acid, and subsequently a small amount (1.5 mL) of homogenate was centrifuged.…”