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The plants’ development process is regulated by genetic and environmental factors, which affect t... more The plants’ development process is regulated by genetic and environmental factors, which affect the biosynthesis, metabolism, transport and signaling pathway of the auxins. The phytohormones play a complex role, exerting direct effects – which influence the cellular division or growth – or indirect effects – interacting with other molecules or phytohormones. In dicotyledonous plants, in the absence of light, the stalks elongate and the leaves remain small, sometimes being reduced to scales, whilst in monocotyledonous plants the stalks remain short and the leaves are elongated. The low light intensity causes the discoloring of the etiolated plants, which lose their green color and turn to a pale yellow color, because the biosynthesis of chlorophyll is favored stimulated by light. The light’s action is positively correlated with that of the temperature and the CO2 concentration.
The UV-B waves are not only a stress factor, but, as part of the Sun’s electromagnetic wave emiss... more The UV-B waves are not only a stress factor, but, as part of the Sun’s electromagnetic wave emissions, have useful information about the waves’ relations with the environmental factors (the ozone layer, the irradiation angle, topographic factors and leaf development).The most susceptible nucleotides to the action of the UV radiation are the ones containing pyrimidine bases (thymine and cytosine).The effect characteristic to UV irradiation is the forming of pyrimidine dimers, which distorts the shape of the DNA molecule, perturbing the replication.Following these changes, the effect may be lethal if the reparatory process is not carried out. To counteract the negative UV radiation effects, the organisms and plants have regenerative mechanisms (photoreactivation, excision repair, recombination replicative repair).
The plants’ development process is regulated by genetic and environmental factors, which affect t... more The plants’ development process is regulated by genetic and environmental factors, which affect the biosynthesis, metabolism, transport and signaling pathway of the auxins. The phytohormones play a complex role, exerting direct effects – which influence the cellular division or growth – or indirect effects – interacting with other molecules or phytohormones. In dicotyledonous plants, in the absence of light, the stalks elongate and the leaves remain small, sometimes being reduced to scales, whilst in monocotyledonous plants the stalks remain short and the leaves are elongated. The low light intensity causes the discoloring of the etiolated plants, which lose their green color and turn to a pale yellow color, because the biosynthesis of chlorophyll is favored stimulated by light. The light’s action is positively correlated with that of the temperature and the CO2 concentration.
The UV-B waves are not only a stress factor, but, as part of the Sun’s electromagnetic wave emiss... more The UV-B waves are not only a stress factor, but, as part of the Sun’s electromagnetic wave emissions, have useful information about the waves’ relations with the environmental factors (the ozone layer, the irradiation angle, topographic factors and leaf development).The most susceptible nucleotides to the action of the UV radiation are the ones containing pyrimidine bases (thymine and cytosine).The effect characteristic to UV irradiation is the forming of pyrimidine dimers, which distorts the shape of the DNA molecule, perturbing the replication.Following these changes, the effect may be lethal if the reparatory process is not carried out. To counteract the negative UV radiation effects, the organisms and plants have regenerative mechanisms (photoreactivation, excision repair, recombination replicative repair).