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PHYSIOLOGICAL AND MOLECULAR ANALYSIS OF VASCULAR TISSUES IN PLANTAGO MAJOR IN RESPONSE TO SOLE OR COMBINED DEFICIENCIES TO NITROGEN AND PHOSPHORUS
Nitrogen and phosphorus are the two macronutrients which play important roles in the plant, both structurally and functionally, e.g., starting from being constituents of cellular integrity to being signal molecules in signal transduction. Since they are required by plants in higher concentrations, it becomes indispensable to replenish their pools in soils by the application of chemical fertilizers. However, this practice is not only costly, the sources of Phosphorus and Nitrogen are not renewable and the excessive application in the form of fertilizers is not environmentally sustainable. Therefore, it warrants a better understanding of the plant responses during the nutrient deficiency because such knowledge will help implement strategies for breeding crops with more efficient use of minerals.
Most prior efforts in studying the molecular and physiological responses to low minerals were focused on roots. However, recently it has been found that shoot-to-root long distance signaling plays an important role in the adaptation of roots to low nitrogen or phosphorus. Here, we measured different physiological and morphological parameters and used RNA-Seq to elucidate the physiological and molecular responses in the vascular tissues of Plantago major, a new model species established in our laboratory, to low nitrogen, low phosphate or combined nitrogen and phosphate starvation. In this study, P major showed reduced photosynthesis and Fv/Fm, increased catalase and ascorbate peroxidase activity, reduced phosphate and nitrate contents in respective treatments. In addition, assessment of root morphological parameters revealed that nutrient deficiencies could lead to higher root densities and increased root to shoot ratios.
For molecular analysis of transcriptome changes, 24 hours of nutrient starvation exhibited an alteration of 33, 221, and 329 genes for the deficiencies of phosphorus, nitrogen and combined nitrogen and phosphorus, respectively. Our study helped to dissect several novel pathways associated with the vascular system in response to the deficiencies of major macronutrients.