Decline in stomatal response to leaf water deficit in Corylus maxima cuttings

Abstract

Many woody species can be propagated from leafy cuttings. However, following rooting, cuttings of Corylus maxima Mill. cv. Purpurea do not always survive the transition from a highly supportive rooting environment (e.g., fog) to a more natural environment where evaporative demand is higher. We found that it is not the supply of water to leaves, but stomatal dysfunction that leads to severe water deficits in the rooted cuttings. Two hours after well-rooted cuttings were transferred from the rooting environment, we were able to relate visible signs of leaf water deficit to high stomatal conductance (g(s)) and low relative water content (R). Small expanding leaves (L3) had unusually high g(s) and lower R than fully expanded leaves (L1). Although high cuticular conductances (g(c)) were occasionally observed in L3, SEM confirmed that increased total leaf conductance (g) was mainly a result of abnormally wide stomatal opening. We measured changes in the ability of stomata to control water loss during rooting by determining stomatal responsiveness to leaf water deficit in detached L1 and L3 harvested from cuttings during the first 75 days after severance from stock plants. Reduced stomatal responsiveness was observed within 7 days of severance, prior to adventitious root formation, and was more pronounced in L3 than in L1. A period of acclimatization after rooting (no leaf wetting, but a vapor pressure deficit of 0.20 kPa) reduced g(s) by 50% in L3 but not in L1, and partially restored stomatal responsiveness in L1 but not in L3. After rooting, the original leaves on the cutting retained substantial capacity for photosynthesis (e.g., in L1, 8 micromol m(-2) s(-1) at a photosynthetic photon flux density of 400 micromol m(-2) s(-1)). The implications of the results for post-rooting acclimatization procedures are discussed.

Effects of leaf wetting and high humidity on stomatal function in leafy cuttings and intact plants ofCorylus maxima

“…Measurements of stomatal pore dimensions indicated more rounded stomatal pores in cuttings of C. maxima than in intact plants. Qualitatively, scanning electron microscopy has also shown this phenomenon in cuttings of C. maxima (Fordham et al 2001). Similarly, the development of stomata in vitro leads to progressively more rounded stomatal pores than the elliptical pores observed in ex vitro stomata (Ziv et al 1987, Santamaria et al 1993, Zacchini et al 1997, and is associated with irregular stomatal function (Marin et al 1988).…”

“…It has been extensively reported that stomata developing during in vitro micropropagation, under very high humidity and low VPD, have a reduced capacity to control water loss in response to desiccation. In C. maxima , we have shown that similar stomatal dysfunction can also occur during the propagation of leafy cuttings (Fordham et al 2001). The present study investigated effects on stomatal sensitivity to other stimuli, and whether it is severance from the stock‐plant or the extremely supportive rooting environment that leads to stomatal dysfunction.…”

“…Purpurea), a widely sought after hardy ornamental tree, is an example of a subject that, when well rooted, is difficult to wean from the rooting environment. In this case, poor survival rates do not appear to be due to poor hydraulic conductance of the adventitious root system (Ford and Harrison‐Murray 1997), but rather to an inability of the stomata to control water loss in response to leaf water deficit (Fordham et al 2001). There are few published studies of changes in stomatal conductance (g s ) during rooting of leafy cuttings (e.g.…”

Natural variation in stomatal response to closing stimuli among Arabidopsis thaliana accessions after exposure to low VPD as a tool to recognize the mechanism of disturbed stomatal functioning

“…In all the mentioned studies, the short-term response of the stomata to VPD was investigated, and the focus was on the stomatal response to high VPD. However, when plants were grown at low VPD, the behaviour of the stomata in response to desiccation or ABA changed and the stomata showed a diminished response to closing stimuli ( Fordham et al ., 2001a, b ; Rezaei Nejad and van Meeteren, 2005 , 2007 , 2008 ; Rezaei Nejad et al , 2006 ; Fanourakis et al , 2011 ; Arve et al , 2012 ; Aliniaeifard and van Meeteren, 2013 ; Aliniaeifard et al , 2014 ). Even when full-grown leaves were transferred from high to low VPD this loss of stomatal response to closing stimuli could be induced ( Rezaei Nejad and van Meeteren, 2008 ).…”

Stomatal response characteristics of Tradescantia virginiana grown at high relative air humidity

“…The problem is thought to be due to the high RH in the culture containers, but it is also clearly affected by the cytokinins in the culture medium (Santamaria et al 1993). Furthermore, a failure of stomata to close properly in response to desiccation or ABA has been shown in rooted leafy cuttings after transferring from the humid conditions of the propagator to one of increased evaporative demand (Fordham et al 2001a, Fordham et al 2001b).…”