title: Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioning.
abstract: Plants of several species, if grown at high relative air humidity (RH ≥85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion.
authors: Department of Plant Sciences, Horticultural Supply Chains Group, Wageningen University, The Netherlands.
authors: Dimitrios
authors: D
authors: Fanourakis
authors: Susana M P
authors: SM
authors: Carvalho
authors: Domingos P F
authors: DP
authors: Almeida
authors: Ep
authors: E
authors: Heuvelink
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects; D000388:Air; D003890:Desiccation; D006813:Humidity; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D018526:Plant Transpiration / Q000187:drug effects / Q000502:physiology; D027826:Rosa / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water; D000040:Abscisic Acid