Photosynthesis and photoprotection inNicotiana tabacumL.in vitro-grown plantlets

Excess irradiance causes early symptoms of senescence during leaf expansion in photoautotrophically in vitro grown tobacco plants

“…Current research concentrates on the development of photoautotrophic systems in which the sugar content in the medium is reduced or eliminated and CO 2 concentration and irradiance are increased (Kozai 1991, Düring and Harst 1996, Nguyen et al 1999, Sha Valli Khan et al 2003, Teixeira Da Silva et al 2006. However, application of high irradiance during cultivation is limited by susceptibility to photoinhibition of both photoautotrophically (Tichá et al 1998, Kadleček et al 2003 and photomixotrophically (Serret et al 1996(Serret et al , 2001 in vitro grown plants.Chronic photoinhibition was found in in vitro photoautotrophically cultured plants already at irradiance of 200 μmol m -2 s -1 (Tichá et al 1998) and was demonstrated as decreased efficiency and/or decreased maximum rate of photosynthesis, decreased Chl a+b content and Chl a/b ratio, increased content and de-epoxidation state of xanthophyll cycle pigments, decreased both maximum and actual photochemical efficiency of photosystem 2 (PS2), and increased non-photochemical quenching (NPQ) (Tichá et al 1998, Kadleček et al 2003.The symptoms of photoinhibition mentioned above are similar to the symptoms of leaf senescence (Yoo et al …”

Morphological and physiological photon flux influence under in vitro culture of apple shoots

“…They also observed a decrease in the content of chlorophyll with the increase of light incidence. Similarly, Nicotiana tabacum plants cultivated in vitro under 380 µmol m -2 s -1 presented a significantly lower content of total chlorophyll than under 80 µmol m -2 s -1 , regardless of the sucrose concentration used in the medium (Kadlecek et al, 2003). Contrary to these results, Serret et al (2001) also reported an increase in the content of total chlorophyll with the increase of the sucrose concentration in the culture media.…”

“…The results indicated that the increase of photon flux could have influenced the biosynthesis and/or the degradation of chlorophylls and carotenoids. The change in the content of photosynthetic pigments might result in a decrease in the capture of light by the light-harvesting complex of the photo system I (LHC I) and photosystem II (LHC II) and in the capacity of electrons transference in the photosynthetic chain (Kadlecek et al, 2003). Pandey et al, (2006) observed that Anoectochilus plants, acclimatized under high irradiance (300 µmol m -2 s -1 ) showed a reduction in the content of chlorophylls a and b and ß-carotenes due to the excess of photons absorbed, resulting in the degradation of the photosynthetic machinery and/or reduction of size of the light-harvesting complex, suggesting that interconversions between chlorophylls a and b were important for the establishment of an adequate a/b chlorophyll rate during the adaptation of leaves to low and high irradiance.…”

Extremely low frequency electromagnetic field generator suitable for plant in vitro studies

“…In an in vitro system, plants are often characterized by a low photosynthetic rate since the availability of sucrose on the media allows plants to use the carbon source from the medium instead of producing carbohydrate through photosynthesis (Kadlecek et al 2003). However, the increase of chlorophyll content of the in vitro plantlets might be an advantage since it can increase the survival rate of the plants in the acclimatization stage (Afreen 2005).…”

“…For instance, tobacco leaves from a plantlet with high irradiance treatment showed a decrease in total chlorophyll content and chlorophyll a/b ratio, but the contents of carotene and xanthophylls pigment were increased (Kadlecek et al 2003). In in vitro plant culture, chlorophyll content might not be affected by media concentration, but increasing the amount of air exchange in the culture vessel would increase the chlorophyll contents (Afreen 2005).…”