The effects of enhanced UV-B radiation on photosynthetic and biochemical activities in super-high-yield hybrid rice Liangyoupeijiu at the reproductive stage

Abstract

We investigated the light reactions, CO 2 assimilation, but also the chloroplast ultrastructure in the upper three functional leaves (flag, 2 nd , and 3 rd leaves) of the Chinese super-high-yield hybrid rice (Oryza sativa L.) Liangyoupeijiu (LYPJ) with ultraviolet-B (UV-B) treatment during reproductive development. Photosynthetic parameters showed that the upper 3 functional leaves of LYPJ entered into senescence approximately 15 days after flag leaf emergence (DAE). Leaves in UV-B treatment exhibited greater efficiency in absorbing and utilizing light energy of photosystem II (PSII), characterized by higher chlorophyll (Chl) content and the whole chain electron transport rate (ETR). However, UV-B radiation reduced activities of Ca 2+ -ATPase and photophosphorylation. The significantly decreased activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was greatly associated with the decline in photosynthetic efficiency. The net photosynthetic rate (P N ) and stomatal conductance (g s ) suffered strong reductions before 25 DAE, and afterwards showed no significant difference between control and treatment. UV-B treatment delayed chloroplasts development of flag leaves. Chloroplast membranes later swelled and disintegrated, and more stromal thylakoids were parallel to each other and were arranged in neat rows, which might be responsible for better performance of the primary light reaction. It is likely that accumulation of starch and an increase in the number of lipid droplet and translucent plastoglobuli were results of an inhibition of carbohydrate transport. Our results suggest that long-term exposure to enhanced UV-B radiation was unlikely to have detrimental effects on the absorption flux of photons and the transport of electrons, but it resulted in the decrease of photophosphorylation and Rubisco activation of LYPJ. The extent of the damage to the chloroplast ultrastructure was consistent with the degree of the inhibition of photosynthesis.

Impact of environmental factors on rice starch structure: A review

“…Crops cultivated between 40°N and 40°S latitudes are exposed to UVB daily doses of 2–9 kJ/m 2 during summer . Even a small increase in incident UVB radiation may cause significant biological effects, since UVB is readily absorbed by a number of important biological macromolecules, such as DNA and proteins . Rice cultivars differ in sensitivity to enhanced UBV .…”

“…Even a small increase in incident UVB radiation may cause significant biological effects, since UVB is readily absorbed by a number of important biological macromolecules, such as DNA and proteins . Rice cultivars differ in sensitivity to enhanced UBV . A decrease in kernel size was observed in response to enhanced UVB , but information is inadequate as to the detailed effects of enhanced UVB on the structural features of rice starch.…”

Roles of osmoprotectants in improving salinity and drought tolerance in plants: a review

“…salinity and drought, that arrest agricultural production throughout the world (Le and McQueen-Mason 2006;Galvani 2007;Gosal et al 2009;Wani et al 2010;Wani and Gosal 2011;Yu et al 2013;Wani et al 2013;Yadav et al 2014). In response to salinity and drought stresses, plants adopt various strategies including modification in different physiological as well as biochemical processes such as signal perceptions and transduction cascades for survival against these stresses (Faical et al 2009;Ranganayakulu et al 2013).…”

Impact of silicon on maize seedlings exposed to short-term UV-B irradiation

“…Similar results were observed in rice plants, where UV-B treated leaves exhibited greater efficiency in absorbing and utilizing energy of PSII. Higher F v /F m implies that UV-B treated leaves of rice plants were more tolerant to photoinhibition (Yu et al 2013).…”