Can the capacity for isoprene emission acclimate to environmental modifications during autumn senescence in temperate deciduous tree species Populus tremula?
2012
Sun, Zhihong | Copolovici, Lucian | Niinemets, Ulo
Changes in isoprene emission (Φᵢₛₒₚᵣₑₙₑ), and foliage photosynthetic (A) rates, isoprene precursor dimethylallyldiphosphate (DMADP), and nitrogen and carbon contents were studied from late summer to intensive leaf fall in Populus tremula to gain insight into the emission controls by temperature and endogenous, senescence-induced, modifications. Methanol emissions, characterizing degradation of cell wall pectins, were also measured. A rapid reduction in Φᵢₛₒₚᵣₑₙₑ and A of 60–70% of the initial value was observed in response to a rapid reduction of ambient temperature by ca. 15°C (cold stress). Later phases of senescence were associated with further reductions in Φᵢₛₒₚᵣₑₙₑ and A, with simultaneous major decrease in nitrogen content. However, during episodes of temperature increase, A and in particular, Φᵢₛₒₚᵣₑₙₑ partly recovered. Variation in Φᵢₛₒₚᵣₑₙₑ during senescence was correlated with average temperature of preceding days, with the highest degree of explained variance observed with average temperature of 6 days. Throughout the study, methanol emissions were small, but a large burst of methanol emission was associated with leaf yellowing and abscission. Overall, these data demonstrate that the capacity for isoprene emission can adjust to environmental conditions in senescing leaves as well, but the responsiveness is low compared with mid-season and is also affected by stress.
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