Physiological And Molecular Mechanisms Of Light Regulation On Plant Growth In Spruce Species

Light is basic element for plant growth and development. Light is not only the energy source of photosynthesis, but also as a kind of signal activate light receptors to control gene expression, protein synthesis and cells metabolism by signal transduction, which plays a very important role on plant physiological metabolic activity. Different illumination factors regulate plant growth and development, which form the adaptation of different plant species to light. To clarify the physiological and molecular mechanism for light regulating plant growth has important theoretical and practical significance. Proper lighting management can effectively extend the growth period of tree species such as Picea, so as to improve the efficiency of seedlings production. To study the differences performance in seedlings growth, nutrients content, plant hormones, and transcriptome level on the basis of a variety of contrast test and taking multiple kinds of spruce provenances, families and clones as material, were in order to clarify the effects mechanisms and optimize control technology, and provide theoretical and technical basis for high efficiency to breeding fine germplasm of spruce. The main research results showed:(1) Light supplemental in the nigh can efficiently promote the seedlings growth of Picea. The seedling height, diameter, new shoots, number of lateral shoots and biomass of Picea with light supplemental treatment were significant higher than those under control. There was the interaction effects between genetic and enviroment, such as the interaction effects between families and lighting time, the interaction effects between light sourses and provenances.(2) Light supplemental in the nigh promoting seedling growth and development by affecting plant physiological activity. The accumulation of gibberellin and auxin content of seedlings were significantly promoted by light supplemental, which promoted seedling growth. Light supplemental signifianctly influence the accumulation of mineral elements, especially phosphorus.The promoting effects of different light qulities on spruce seedlings growth were different in the process of light supplemental. Light quality mainly by influencing the activity of photosynthetic organ and Benson Calvin cycle enzymes activity or the relevant gene expression to change the photosynthesis of plants. Light cause PS II and PS I light absorption of the mass unbalance and the subsequent two light electron flow of unbalanced system. Compared with light red and compound light, far-red light and blue light were mainly inhibit photosynthetic electron transport, calvin cycle and related genes changes which cause the lower net photosynthetic rate (Pn). Blue light treatment also affected gibberellin and light signal transduction to inhibit growth.(4) Light quality regulates seedling growth by altering the expression of corresponding genes. The seedlings illuminated by red light had the higher gibberellins (GAs) level and the lower indoleacetic acid (IAA) compared to those of the seedlings illuminated by blue light, which may be related to different expression genes in the hormone signal transduction. The DEG classifications revealed extensive blue-light-associated upregulation in Norway spruce. AUXIN-RESISTANT1 (AUX1), AUX/IAA genes, auxin-inducible genes, and early auxin-responsive genes [(auxin response factor (ARF) and small auxin-up RNA (SAUR)] were all upregulated under blue light compared with red light, which might have yielded the higher IAA level. DELLA and phytochrome-interacting factor 3 (PIF3), involved in negative GA signaling, were also upregulated under blue light, which may be related to the lower GA level. Light quality also affects endogenous hormones by influencing secondary metabolism. Blue light promoted phenylpropanoid biosynthesis, phenylalanine metabolism, flavonoid biosynthesis and flavone and flavonol biosynthesis, accompanied by upregulation of most of the genes in their pathways. In conclusion, red light may promote stem growth by regulating biosynthesis of GAs, and blue light may promote flavonoid, lignin, phenylpropanoid and some hormones (such as jasmonic acid) which were related to plant defense in Norway spruce, which might reduce the primary metabolites available for plant growth.Light supplemental in the nigh promote accumulation of auxin, gibberellin, and effecte the metabolism of mineral elements. The effective spectrum influences the activity of photosynthetic organ and related enzymes, and the expression of genes related to endogenous hormones and secondary metabolites, which affects the photosynthetic efficiency. Families, provenances genetic differentiation and phenotypic plasticity to light supplemental were give rise to the different response of different families, provenances on light supplemental, which make it is possible to selected superior families, provenances under light supplemental.