Transformation Work Carrying On In Italy on fruit trees

Modifications of plant habitus by manipulation of phytochrome genes. Shading can be a major source of stress for plants of many orchard species. In orchard systems, where plants are grown as dense populations, shading is mostly caused by neighbouring plants of similar size and genotype. Agricultural plant productivity is a complex function involving resource acquisition and partitioning among the various plant organs. Photosynthesis and nutrient uptake from soil represent the primary biomass production processes, but resource partitioning crucially determines elevated economic value biomass production. Partitioning of assimilates may be influenced by and/or influence tree architecture, which plays a major role in successful economic exploitation of modern orchard systems, as orchard techniques now focus mainly on growth control by means of crop management practices and/or selection of low vigour genotypes (rootstocks and/or cultivars). Light is scattered within plant tissues and plant pigments absorb mainly the ultraviolet ( < 400 nm) and visible (400 nm    700 nm) photons. In contrast, fewer far-red (FR;   700 nm) quanta are absorbed, and most of them exit the plant in the form of scattered radiation. Therefore, within plant canopies, the light environment is characterised by low levels of blue and red light, the visible wavelengths that are most absorbed by chlorophylls, and high levels of FR. Changes in the R:FR ratio are used by plants to sense the proximity of neighbouring individuals, change in canopy density and leaf shading. Thus variations in R:FR caused by preferential absorption of R light by chlorophylls are thought to be able to shift the amount of phytochrome present as Pfr (the Fr-absorbing form of phytochrome). The change in Pfr would then provide a cellular signal which, being related to the degree of shading, could be used by plants in the understory to control developmental timing and morphogenesis. Changes in photon fluence rate also convey information about the proximity of neighbours in plant stands. For plants, branches, and leaves growing underneath other vegetation or a change in canopy LAI will cause variation in irradiance, which may serve as an input signal for the systems that control shade acclimation at different levels, from chloroplast physiology to whole plant allometry. Moreover, changes in light fluence rate may also function as early proximity signals in even height canopies, because the fluence rate sensed by vertically orientated stems is more affected by changes in canopy density by the light environment of horizontal or diaphotropic leaves. Plants can sense fluence rate in two ways: 1) indirectly, by sensing changes in the availability of photosynthetic products (sugars), or 2) more directly, by sensing molecular signals closely related to the photoexcitation