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How does the VPD response of isohydric and anisohydric plants depend on leaf surface particles?
Author(s) -
Burkhardt J.,
Pariyar S.
Publication year - 2016
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1111/plb.12402
Subject(s) - beech , vapour pressure deficit , transpiration , scots pine , horticulture , botany , agronomy , biology , chemistry , photosynthesis , pinus <genus>
Atmospheric vapour pressure deficit ( VPD ) is the driving force for plant transpiration. Plants have different strategies to respond to this ‘atmospheric drought’. Deposited aerosols on leaf surfaces can interact with plant water relations and may influence VPD response. We studied transpiration and water use efficiency of pine, beech and sunflower by measuring sap flow, gas exchange and carbon isotopes, thereby addressing different time scales of plant/atmosphere interaction. Plants were grown (i) outdoors under rainfall exclusion ( OD ) and in ventilated greenhouses with (ii) ambient air ( AA ) or (iii) filtered air ( FA ), the latter containing <1% ambient aerosol concentrations. In addition, some AA plants were sprayed once with 25 mM salt solution of ( NH 4 ) 2 SO 4 or Na NO 3 . Carbon isotope values (δ 13 C) became more negative in the presence of more particles; more negative for AA compared to FA sunflower and more negative for OD Scots pine compared to other growth environments. FA beech had less negative δ 13 C than AA , OD and Na NO 3 ‐treated beech. Anisohydric beech showed linearly increasing sap flow with increasing VPD . The slopes doubled for ( NH 4 ) 2 SO 4 ‐ and tripled for Na NO 3 ‐sprayed beech compared to control seedlings, indicating decreased ability to resist atmospheric demand. In contrast, isohydric pine showed constant transpiration rates with increasing VPD , independent of growth environment and spray, likely caused by decreasing g s with increasing VPD . Generally, Na NO 3 spray had stronger effects on water relations than ( NH 4 ) 2 SO 4 spray. The results strongly support the role of leaf surface particles as an environmental factor affecting plant water use. Hygroscopic and chaotropic properties of leaf surface particles determine their ability to form wicks across stomata. Such wicks enhance unproductive water loss of anisohydric plant species and decrease CO 2 uptake of isohydric plants. They become more relevant with increasing number of fine particles and increasing VPD and are thus related to air pollution and climate change. Wicks cause a deviation from the analogy between CO 2 and water pathways through stomata, bringing some principal assumptions of gas exchange theory into question.