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How to monitor the acclimatization of micropropagated plants - From in vitro to the field?

Publication . Osório, Maria Leonor; Gonçalves, Sandra; Coelho, N.; Romano, Anabela; Osório, Júlio

The high mortality experienced by plants during ex vitro transplantation stage is the major bottleneck in large scale application of micropropagation. The abnormal physiological and anatomical characteristics of micropropagated plantlets require that they should be gradually acclimatized to the environment of the greenhouse or field. Environmental factors, especially relative humidity and irradiance, play a critical role in both physiological and biochemical functions, namely water relations, gas exchange, photosynthetic efficiency and water oxidation, during transition from in vitro to ex vitro conditions. Throughout this period of transition and acclimatization substantial changes in those characteristics are necessary to achieve a successful micropropagation. This adaptation should be accurately monitored using relevant physiological parameters including pigment content, chlorophyll a fluorescence imaging, net photosynthetic rate, transpiration rate, and stomatal conductance. Growth traits and oxidative stress markers, such as electrolyte leakage, lipid peroxidation and hydrogen peroxide content, should be also analyzed. These parameters must be assessed during the course of ex vitro acclimatization in several periods and compared with those of plants growing in their natural habitat. The performance plants of Tuberaria major, an endangered species endemic from the Algarve region (Portugal), during their acclimatization through indoor-to-outdoor conditions was monitored using several physiological and biochemical traits as indicators. In view of the results, we concluded that the transplantation protocol described can be used for restoration purposes, contributing to the preservation of the species. © ISHS 2013.

2013Journal article

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Reflectance indices as nondestructive indicators of the physiological status of Ceratonia siliqua seedlings under varying moisture and temperature regimes

Publication . Osório, Júlio; Osório, Maria Leonor; Romano, Anabela

We investigated the use of spectral reflectance techniques to monitor the physiological responses of Ceratonia siliqua L. seedlings exposed to different levels of water availability under normal (25 : 18 degrees C, day : night) and elevated (32 : 21 degrees C, day : night) temperatures. Three spectral reflectance indices (photochemical reflectance index, PRI; water index, WI; red edge position, REP) were measured along with water status, chlorophyll fluorescence and chlorophyll concentration variables in the leaves of well watered, moderately stressed, severely stressed and rehydrated plants under each temperature regime. The PSII effective photochemical efficiency (phi(2)) and the intrinsic efficiency of open PSII centres (F-v'/F-m') correlated significantly with PRI, and these three variables loaded heavily onto the same principal component of a three-factor principal component analysis solution. Water concentration (WC) and the succulence index (SI) were more strongly correlated with WI than either water potential (Psi(PD)) or relative water content (RWC). Accordingly, WI, WC and SI were combined in the second principal component, and Psi(PD) and RWC in the third. Our results provide clear evidence for interaction between water availability and temperature in the WI and the PRI response segments of the reflectance curves. Elevated temperature inhibited the recovery of WI spectral segments more than that of the PRI segments in SS plants. REP showed a strongly positive linear relationship with leaf total chlorophyll concentration across all water and temperature treatment combinations. PRI, WI and REP are therefore reliable markers that can be used to monitor phi(2), WC and total chlorophyll concentration, respectively, in C. siliqua seedlings under drought and temperature stress.

2012Journal article

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