c7.5.7 – Stomatal sluggishness as a response to ozone exposure in species of different physiognomic class

Paoletti E* (1), Grulke NE (2)

(1) IPP-CNR, v. Madonna del Piano 10, I-50019 Sesto Fiorentino (FI), Italy; (2) US Forest Service, 4955 Canyon Crest Drive, Riverside, CA 92507 USA
Collocazione: c7.5.7 – Tipo Comunicazione: Presentazione orale
7° Congresso SISEF *
Sessione 5: “Risposte ai disturbi ambientali” *

Contatto: Elena Paoletti (e.paoletti@ipp.cnr.it)

Abstract: Tropospheric ozone (O3) pollution is a global climate change phenomenon. To explain loss of plant yield and productivity, attention has traditionally focused on ozone effects on photosynthesis. The photosynthetic impairment has been attributed to the decline in the efficiency in carboxylation, the electron transport system, and/or direct effects on stomata. Closure of stomata is a defence from ozone entry into the leaf, and has often been described as a secondary response to ozone (i.e. when stomatal conductance decreases following a decrease in intercellular ozone concentration), but an understanding of stomatal responses to ozone is still imperfect. Incomplete or sluggish stomatal closure can occur with moderate and above ozone exposures. Sluggish stomatal response with ozone exposure is here defined as a delayed reaching a stable conductance relative to leaves without ozone exposure. Our aim was to test whether ozone exposure causes stomata to be sluggish in both crops and forest species. Stomatal responses to light variation and assimilation curves in response to CO2 were tested in three species: ozone-sensitive and ozone-insensitive snap bean (Phaseolus vulgaris) cultivars, and seedlings of California black oak (deciduous broadleaf, Quercus kelloggii) and blue oak (winter green broadleaf, Quercus douglasii). The effects of 1-month (snap beans) and 2-month (oaks) ozone exposure (70 ppb over 8 hours per day) were investigated. Results suggest sluggish stomatal responses to fluctuating stimuli are both an effect of ozone exposure and a reason of increased ozone sensitivity in snap bean cultivars, as they imply higher ozone uptake before stomata reach an equilibrium. Sluggishness increased the time to open and close stomata after abrupt changes in light level. The effects of ozone and cultivar/species on photosynthesis were not correlated to the effects on stomatal sluggishness, suggesting that antioxidative processes were in progress. Stomatal aberrations in response to ozone exposure have been largely ignored in current modeling efforts of ozone effects on plants. The consequence is to minimize the importance of ozone impact on plant water balance and susceptibility to water stress and fire.

Citazione: Paoletti E , Grulke NE (2009). Stomatal sluggishness as a response to ozone exposure in species of different physiognomic class . 7° Congresso Nazionale SISEF, Isernia – Pesche (IS), 29 Set – 03 Ott 2009, Contributo no. #c7.5.7