Investigation of possible silicon-aluminium obstructions in the vascular bundle in Pinus caribaea var. Hondurensis related to plant senescence and death

This work was carried out based on the hypothesis that polymers associated with silicone (Si) would be obstructing tracheid, therefore contributing to a nutritional collapse of Pinus caribaea forest bulks, in the Triângulo Mineiro and Alto Paranaíba (MG) plains. Previous studies showed a narrow relationship between these physiologic patterns with nutritional deficiencies. However, it is known that seeds used in the establishment of these bulks presented great genetic variability well expressed in diversity of plant behavior, inasmuch as part of them remains healthy and the others start a changeable intensity senescence, which ends up in the death of the plant. In this study, it was sampled segments of root and apical shoots of apparently normal (green needles) plants at different senescence stages (yellow needles) and dead plants. Those samples, after being dried until critical point, were observed by scanning electron microscope coupled to an X-ray microprobe. It was noted the presence of Si and Al in xylem and phloem tissues in the aerial section as well as in the roots, and the greatest contents were found in xylem of the plants. However, it was not observed any obstruction or any presence of Si-Al bodies in the conducting tissues of the analyzed parts. But, it was observed that the presence of Si associated to Al occurred according to a 2.6 order Al/Si ratio. Data also revealed that Si variation amplitude is 1.5 times greater than the Al variation amplitude. It concluded that Si variation amplitude is greater than the one of Al, which establishes a variation relationship (Si-Al).

Pine tree; Abiotic disease; Savannah phase soil; Silviculture

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