Plant growth and development, which determinate plant form, require the integration of a variety of environmental signals with the intrinsic genetic program. Fundamental to this process are several growth regulators called the plant hormones or phytohormones. In accordance with definition, the plant hormones are signal molecules produced within the plant and occur in extremely low concentrations.

Cyclic adenosine 3’:5’-monophosphate and cyclic guanosine 3’:5’-monophosphate, common- ly know as cAMP and cGMP, are key second messengers in living organisms ranging from bacteria to Homo sapiens. Cyclic AMP and cyclic GMP are produced from ATP and GTP by the action of adenylyl cyclase and guanylyl cylase and are hydrolyzed to AMP and GMP by the cyclic nucleotide phosphodie- sterase. The natural occurrence of cyclic nucleotides in higher plants is now established, as is the presence of enzymes involved in their metabolism.

It is almost 70 years since Mikhail Chailakhyan put forward his hormonal theory of flowering induction, which envisaged the leaves producing and exporting to the shoot apex a specific floral hormone which he called „florigen”. The search for isolation of mythical florigen ended unsuccessfully. However, the investigations have shown that fundamental for flower induction is cooperation between family of flowering gens which express high activity in cells of vascular bundles. The mobile flowering signal could be a product of one of them in the form of transcript mRNA or protein.

Flowering is a complex physiological process which depends on many internal and external factors. Transition from vegetative to generative stage in Arabidopsis thaliana is controlled by several developmental pathways. Among them are: giberellin, autonomous, vernalization, light quality and pho- toperiod pathways. In most of plants flowering depends on light and temperature. Light quality pathway is connected with the shade-avoidance syndrome. Acceleration of flowering during shade-avoidance syn- drome is controlled by three major molecules: phytochrome B, PFT1 protein and FT gene.

The symplasmic transport of protein and RNAs has emerged as a novel mechanism of cell to cell communication in plant. This movement can occur in selective or a non-selective way between neighbouring cells, tissues or in whole plant. The symplasmic transport is under control both during plant development and in response to environmental conditions. The knowledge about RNAs and proteins that move from cell to cell through plasmodesmata and in the whole plant though phloem is still growing. The transport of mRNA such genes like KN1 or CmNCAP1, has been also described.

Nucleotides are among the most important compounds in all living organisms. They partici- pate in many biochemical processes in cells. They are precursors for nucleic acid synthesis, an energy source and precursors for components of primary and secondary metabolic products. Therefore, the metabolism of nucleotides are crucial for the growth and development of all organisms.

Circadian clock is one of the most fascinating adaptations to life on Earth. Thanks to the internal clock organisms can not only respond to the periodic succession of day and night, but also measure the length of day, which is an indicator of the seasons. Endogenous clock generates rhythms of approximately 24 hours . Setting the clock is done mainly through changes in temperature and light conditions at dawn and dusk.

COP9 Sygnalosome ( CONSTITUTIVE PHOTOMORPHOGENIC 9) referred more often abbreviated as CSN ( COP9 signalosome called ) is a multiprotein complex nuclear commonly occurring Eucariotes . The results of many diverse studies have shown CSN participate in a wide range of vital processes , such as photomorhogenesis , regulation of cell cycle or cell differentiation . Increasingly complex COP9 signalosome is associated with the control of the ubiquitin mediated protein degradation .

Mechanisms of flowering plants. II. Molecular Genetic control of induction of flowering.

Mechanisms of flowering plants. I. The physiological and environmental conditions.