Efeito do alagamento nas respostas morfofisiológicas em porta-enxertos de cacaueiro (Theobroma cacao L.)
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Data
2020-02-28
Autores
Pinto, Maria Luiza Pereira Barbosa
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Universidade Federal do Espírito Santo
Resumo
The response of cacao to the reduction of oxygen in the soil and recovery after suspension of stress is associated with the plasticity capacity of each genotype, however studies that evaluate the influence of the rootstock on the response to stress are scarce. The objective of this work was to carry out the morphophysiological characterization of different genotypes as rootstocks of cocoa under flooding condition, aiming to identify markers for the early selection of plants and the indication of more tolerant seedlings for planting in areas subject to intermittent flooding. The rootstocks evaluated were TSH-1188, Cepec-2002, Pará, Esfip-02, SJ-02, and PS-1319 as a graft. Grafted seedlings were subjected to flooding for 60 days and the recovery capacity was assessed after the stress was lifted. The fluorescence of chlorophyll a, gas exchange and the relative green content were evaluated during the periods of flooding and recovery. At the end of 60 days of vi flooding and 30 days of recovery the development and growth of plants, the extraction of carbohydrates and anatomy of the stem and leaf were characterized, the extraction of pigments was carried out at the end of the flooding. The flooding caused a decline in photosynthetic capacity after 7 days of flooding, the accumulation of biomass and growth decreased due to the flooding in the substrate, with a 20% reduction in the total dry mass in the flooding. After the ETo / RC recovery and the DIo / RC presented values equal to that of the control plants, the rootstocks recovered their development and accumulation of biomass, except for the NF. All genotypes reduced liquid photosynthetic assimilation, stomatal conductance and transpiration, except for SJ-02, which was constant. There was an accumulation of total soluble sugar in the leaves during flooding, and the pigments were degraded. There was the formation of lenticels in all rootstocks, Pará did not show differences in stomatal density between environments. The negative effect of flooding could be perceived by the reduction in the maximum quantum yield of primary photochemistry, which was below the ideal values of 0.75-0.85, for plants without stress. The time of exposure to flooding caused limitations in gas exchange, the rootstock SJ-02 presented the lowest rates of gas exchange in the control plants and in the flooding there were no considerable variations. The rootstocks Cepec-2002 and Esfip-02 showed a higher accumulation of carotenoids. There was an accumulation of soluble sugars in the leaves and roots during flooding, the Cepec-2002 and Pará rootstocks accumulated less starch in the roots. After the recovery, the performance index values for the absorption and maximum quantum yield of the primary photochemistry began to recover, indicating that the damage caused was not irreversible. Biomass accumulation, development and growth reduced during flooding. The rootstocks TSH-1188 and Esfip-02 showed greater accumulation of MSC, MSR and DC. After recovery, all biomass and development parameters were able to recover, except the NF. Through the PCA it was possible to confirm that the plants show different behaviors in the environments. After recovery, rootstocks normalized their gas exchange, carbohydrates and anatomy, showing that the root system was able to restore its functions
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Palavras-chave
Cacau , Fluorescência da clorofila A , Trocas gasosas , Cocoa , Chlorophyll A fluorescence , Gas exchange