Alterações morfoanatômicas, fisiológicas e crescimento de mudas de dendezeiro (Elaeis guineensis jacq.) induzidas por microrganismos.

Abstract

The oil palm (Elaeis guineensis Jacq.) is a species from the African continente, belonging to the Arecaceae family, with great importance due to the commercialization of palm kernel oils extracted from their fruits and used in the food, pharmaceutical, cosmetics and biofuels. In Brazil, the state of Pará has a prominent position in the production of palm oil, due to the edaphoclimatc conditions favorable to the crop and the number of degraded áreas that can be reused with the cultivation of oil palm. In recente decades, oil palm cultivation has expanded in the region, but the processo of producing oil palm seedlings requires a long period in the nursery and high doses of fertilizers, which is why it is necessary to use techniques that favorable to the growth of oil palm seedlings and improve efficiency in the use of fertilizers. The use of plant growth-promoting microorganisms tends to be a sustainable alternative in the formation of robust seedlings, more precocious and lower cost-benefit. Among these microorganisms, fungi of the Trichoderma genus and rhizobacteria such as Serratia marcescens and Bacillus amyloliquefaciens stand out, these microorganisms have the ability to promote growth in plants due to several direct and indirect mechanisms. Therefore, the objective of this work was to evaluate leaf and root morphoanatomical changes, associated with photosynthetic performance and root development in oil palm seedlings, induced by inoculation with growth-promoting microorganisms. Thus, two experiments werw carried out in a completaly randomized design, the first consisted of oil palm seedlings inoculated with B. amyloliquefaciens, S. marcescensand a pool of four isolates of T. asperellum (UFRA-06, UFRA-09, UFRA-12 and UFRA 52) and compared with control seedlings (not inoculated), six months after inoculation of the plants, it was observed that all microorganisms tested promoted morphoanatomical and physiological changes favorable to growth in oil palm seedlings. The application with these microorganisms stimulated na in the thickness of the leaf blade, the mesophyll and the number and diameter of the metaxylem vessel elements, this may have contributed to the accumulation of chlorophylls and consequently the increase in the potential activity of photosystem II, at the rate electron transport, photochemical dissipation and net assimilatin of CO2 in biostimulated plants, generally resulting in the promotion of growth in oil palm seedlings. The second experimente aimed to evaluate root morphoanatomical changes favorable to improving fertilization efficiency and growth in oil palm seedlings inoculated with isolates of Trichoderma spp. oil palm seedlings treated with 50% of the recommended fertilization were inoculated with the Trichoderma FT-02 isolate and the pool with four T. asperellum isolates (UFRA-06, UFRA-09, UFRA-12 and UFRA-52) and compared roo non-inoculated plants with 50% and 100% of the recommended fertilization. The biostimulated 12 month old plants showed thickening of the córtex, na increase in the number and diameter of the metaxylem vessel elements and the vascular cylinder, in addition, th FT-02 isolate provided na increase in the surface área and root volume in comparison to the plants not inoculated. In general, inoculation with microorganisms in oil palm seedlings induced positive morphoanatomical and fuctional changes, which allowed an improvement in photosythetic performance, root development and contributed to the promotion of growth.