Name: MARIA LUIZA PEREIRA BARBOSA PINTO
Publication date: 28/02/2020
Advisor:
Name |
Role |
|---|---|
| SARA DOUSSEAU ARANTES | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ANDREIA BARCELOS PASSOS LIMA GONTIJO | Internal Examiner * |
| SARA DOUSSEAU ARANTES | Advisor * |
Summary: 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 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.
