Water Loss and Morphological Modifications in Leaves During Acclimatization of Cork Oak Micropropagated Plantlets

Abstract

This study characterises some aspects of foliar anatomy of cork oak micropropagated plantlets, and rates of water loss by different types of leaves during the acclimatization period. Water loss from leaves of in vitro cultured plantlets was much higher than that of acclimatized plants or seedlings. Leaves from in vitro plantlets lost 53% of their water within the first 30 min under water stress conditions, while leaves from acclimatized plants lost 14%. Leaves of in vitro grown plants presented open stomata and collapsed guard cells, while acclimatized leaves presented closed stomata. Shade-leaf structure was observed in transverse sections of in vitro leaves, with large intercellular air spaces and a low mesophyll cell density, but with a differentiated palisade cell layer. Leaves from acclimatized plants showed a sun-leaf structure with small intercellular air spaces, high cell density and two or three palisade cell layers. During acclimatization leaf thickness increased, as well as cell compactness and differentiation. Stomatal density, stomatal aperture and guard cell protuberance decreased during the acclimatization period, while trichome density increased.

Use of Biotechnological Methods to Support the Production of New Peach Hybrids

“…Similar results for the leaf structure of in vitro micropropagated and in vivo adapted plants were obtained by Calvete et al [63] in Fragaria ananassa Duch. (Rosaceae) plants, Romano and Martins-Loucao [12] in the culture of Quercus ruber L. (Fagaceae), Yang and Yeh [64] in Calatheaor bifolia (Linden) H. Kenn. (Marantaceae), Batagin-Piotto et al [65] in the culture of Bactris gasipaes (Arecaceae), Werner et al [14] in the culture of Crambe abyssinica Hochst (Brassicaceae), I. Mitrofanova et al [66] in Canna indica L. (Cannaceae), O. Mitrofanova et al [15] in Lavandula angustifolia Miller.…”

“…In turn, the mechanisms of species, forms and cultivars adaptation to environmental conditions are determined by their anatomical, morphological, physiological and biochemical structural features. The acclimatization process, that is, the transfer of a plant from in vitro to ex vitro conditions, is often a critical stage for a seedling survival [12][13][14][15][16]. There are a number of differences between in vitro and ex vitro conditions in terms of light intensity and quality, relative air humidity, availability of nutrients, substrates and gas concentration.…”

Photosynthetic capacity, growth and water relations in ‘Golden’ papaya cultivated in vitro with modifications in light quality, sucrose concentration and ventilation

“…As a result, the plantlets cultured in vitro have a low capacity to control water loss when subjected to ex vitro conditions (Ziv 1995). This inability to control water loss is mainly due to limited or reduced stomatal functioning (i.e., the stomata remain completely open) (Sáez et al 2012), malformation of the epidermal wax layer (Cassells and Walsh 1994;Kitaya et al 2005) and the incomplete formation of the leaf mesophyll (Romano and Martins-Loução 2003). Water loss can be extreme after a plantlet grown in a CM using a culture flask without ventilation is transplanted into an ex vitro environment.…”

Perda de água e modificações anatômicas em folhas de plantas de bananeiras micropropagadas durante a aclimatização

“…Reduzido conteúdo relativo de água em tecidos foliares in vitro foi observado por ROMANO & MARTINS-LOUÇÃO (2003) em carvalho (Quercus suber L.). Segundo esses autores, folhas de plantas in vitro apresentaram uma perda de 53% do conteúdo relativo de água logo nos primeiros 30 minutos de exposição à temperatura de 21°C±2°C e umidade relativa de 50%, ao contrário do que ocorreu com folhas novas de plantas após um mês de aclimatização e folhas persistentes, as quais perderam apenas 14% e 29% do seu conteúdo de água, respectivamente.…”

“…Dentre as principais características das plantas cultivadas in vitro, destaca-se a baixa regulação da perda de água, decorrente, principalmente, da limitada ou pouca funcionalidade dos estômatos e da deficiente formação de cera epicuticular (LAMHAMEDI et al, 2003), além de reduzido desenvolvimento do mesofilo foliar, especialmente os parênquimas clorofilianos e feixes vasculares (SANDOVAL et al, 1994;AMÂNCIO et al, 1999;GONÇALVES et al, 2000;ROMANO & MARTINS-LOUÇÃO, 2003). Os estômatos possuem considerável importância nessas alterações, pois o movimento de água contida nos espaços intercelulares para a atmosfera ocorre quase que completamente por difusão do vapor de água através deles, cujo principal mecanismo de controle é a resistência estomática (TAIZ & ZEIGER, 2004).…”