Low air humidity during cultivation promotes stomatal closure ability in rose

Abstract

In greenhouse horticulture, evaporative demand varies between seasons. For instance, plants are typically exposed to low relative air humidity (RH) during summer, whereas elevated RH prevails in winter. Since high RH during cultivation impairs stomatal functioning, some opposite changes might be expected, when plants are subjected to long-term low RH. To investigate this, Rosa hybrida 'Pasadena' was cultivated at 40, 60 or 90% RH. Plant performance, transpiration, stomatal closing ability and anatomy were recorded. As RH increased from 40 to 60% as well as from 60 to 90%, plants showed larger leaf area and thinner leaves. Plant water loss was mainly determined by ambient RH in the growing environment, with stomatal conductance (g s) being of secondary importance. With increasing RH, plant transpiration declined at growth environment. Larger stomata were found at 90% RH, as compared to 40 or 60%. Stomatal physiology was considerably affected by 90% RH, including reduced g s oscillations within the photoperiod, attenuated opening response following dark/light transition, as well as reduced closing response upon darkening. The plants cultivated at 90% RH had a reduced ability to control water loss upon water deprivation, compared to those grown at 60%. In contrast, cultivation at 40% RH resulted in stomata, which were much more responsive to water stress, compared to 60% RH-grown plants. This superiority was dual: lower transpiration rate combined with less severe leaf drying to induce stomatal closure. In conclusion, low RH during cultivation, which is typical during summer, leads to thicker leaves with very responsive stomata.

Stomatal conductance bears no correlation with transpiration rate in wheat during their diurnal variation under high air humidity

“…Devi, Sinclair & Vadez (2010) found that Tr increased over VPD rising, with a break point occurring in some genotypes above which there was little or no further increase in Tr of peanut. Stomatal conductance declined with VPD increasing (Leonardi, Guichard & Bertin, 2000;Talbott, Rahveh & Zeiger, 2003), or RH declining (Fanourakis et al, 2016(Fanourakis et al, , 2019, which implied that Tr did not decline with g s reducing, but increased with VPD rising. And the occurrence of Tr breakpoint might be due to that g s continuously declined and turned to be the restricting factor of Tr.…”

Peer Review #1 of "Stomatal conductance bears no correlation with transpiration rate in wheat during their diurnal variation under high air humidity (v0.1)"

“…Devi et al (2010) found that Tr increased over VPD rising, with a break point occurring in some genotypes above which there was little or no further increase in Tr of peanut. Stomatal conductance declined with VPD increasing (Leonardi, Guichard & Bertin 2000;Talbott, Rahveh & Zeiger 2003), or RH declining (Fanourakis et al 2016;Fanourakis et al 2019), which implied that Tr did not decline with g s reducing, but increased with VPD rising. And the occurrence of Tr breakpoint might be due to that g s continuously declined and turned to be the restricting factor of Tr.…”

An Automatic Method for Stomatal Pore Detection and Measurement in Microscope Images of Plant Leaf Based on a Convolutional Neural Network Model

“…Pore area is dynamically adjusted by changes in pore aperture, since pore length is rather rigid during the opening and closure of stomata [10,11]. Active pore aperture adjustments in response to internal (e.g., water status) and external (e.g., environmental) factors are physiologically regulated [12][13][14][15]. Instead, pore length and stomatal density are anatomical features that are set during leaf elongation [10,16].…”