Abstract
BackgroundHigh temperature, whether transitory or constant, causes physiological, biochemical and molecular changes that adversely affect tree growth and productivity by reducing photosynthesis. To elucidate the photosynthetic adaption response and examine the recovery capacity of trees under heat stress, we measured gas exchange, chlorophyll fluorescence, electron transport, water use efficiency, and reactive oxygen-producing enzyme activities in heat-stressed plants.ResultsWe found that photosynthesis could completely recover after less than six hours of high temperature treatment, which might be a turning point in the photosynthetic response to heat stress. Genome-wide gene expression analysis at six hours of heat stress identified 29,896 differentially expressed genes (15,670 up-regulated and 14,226 down-regulated), including multiple classes of transcription factors. These interact with each other and regulate the expression of photosynthesis-related genes in response to heat stress, controlling carbon fixation and changes in stomatal conductance. Heat stress of more than twelve hours caused reduced electron transport, damaged photosystems, activated the glycolate pathway and caused H2O2 production; as a result, photosynthetic capacity did not recover completely.ConclusionsThis study provides a systematic physiological and global gene expression profile of the poplar photosynthetic response to heat stress and identifies the main limitations and threshold of photosynthesis under heat stress. It will expand our understanding of plant thermostability and provides a robust dataset for future studies.
Highlights
High temperature, whether transitory or constant, causes physiological, biochemical and molecular changes that adversely affect tree growth and productivity by reducing photosynthesis
Response of the photosynthetic rate to heat stress To examine the effects of high temperature on poplar photosynthesis, we measured the dynamic Pn, Ci, Stomatal conductance (Gs), transpiration rate (Tr), and Intrinsic water use efficiency (iWUE) over a time course of high temperature treatment (0 h, 3 h, 6 h, 12 h, 24 h) (Figure 1A-E)
Pn, Gs, Tr and Ci were significantly lower in heat-treated plants than in control plants, but iWUE was significantly higher
Summary
Whether transitory or constant, causes physiological, biochemical and molecular changes that adversely affect tree growth and productivity by reducing photosynthesis. In Populus euphratica, heat stress causes a decrease in PSII abundance and an increase of Photosystem I (PSI); it induces photosynthetic linear. Transitory or constant high temperature causes morphological, physiological, and biochemical changes that reduce photosynthesis and limit plant growth and productivity [2,6]. Moderate heat stress causes a reversible reduction of photosynthesis; increased heat stress causes irreversible damage to the photosynthetic apparatus, resulting in greater inhibition of plant growth [7]. A fundamental understanding of the response of photosynthetic physiology and related gene expression under heat stress may help to improve the thermostability of plants and limit the adverse effects of climate change on crop yield
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