TOLERANCE, LETHAL TEMPERATURE AND ACCLIMATIZATION MEMORY OF Eucalyptus SUBJECTED TO FROST

Name: ELAYNE KÁTIA DOS SANTOS GALVÃO

Publication date: 27/05/2024

Examining board:

Namesort descending Role
DAIANI BERNARDO PIROVANI Examinador Externo
ELZIMAR DE OLIVEIRA GONCALVES Examinador Externo
JOSE EDUARDO MACEDO PEZZOPANE Presidente
MANOEL TEIXEIRA DE CASTRO NETO Examinador Externo
VALERIA HOLLUNDER KLIPPEL Examinador Externo

Summary: Climate change has increased the frequency of extreme events, affecting global forestry, especially in eucalyptus plantations. In southern Brazil, a prominent region in the production of this species, seasonal events challenge the productivity of eucalyptus crops. In this context, the objective of this research was to evaluate the tolerance to tolerance of eucalyptus clones recommended for the region (Eucalyptus urophylla x E. grandis, E. saligna, E. dunnii and E. benthamii), to verify if it is possible to induce tolerance to tolerance in the hybrid E. urophylla x E. grandis through cold acclimatization, also determining the duration of the memory induced. In a climate-controlled chamber, the tolerance to tolerance study was carried out, changes of the aforementioned clones were tested for their tolerance in tolerance simulations at temperatures of -1.5; -2.2; -2.9; -3.4; -4.4 and -6.2 °C. After the sessions, the gas exchange configurations, visual damage index, electrolyte extravasation at lethal temperature (TL50) were evaluated and biochemical analyses were performed quantifying soluble sugars, flavonoids, phenols and anthocyanins. In the acclimation study, E. grandis x E. urophylla seedlings were divided into two groups: one controlled to a period of cold acclimation (5°C to 15°C) and the other, control (without acclimation), maintained at temperatures of 12°C to 27°C, both for 21 days with a 10-hour photoperiod. Subsequently, they were tested for their acclimation memory at 15, 45 and 60 days. The study of the duration of acclimation memory was carried out at a temperature of -4.4°C, determined in a previous test carried out at time zero, using temperatures of -2.0; -3.0; -3.5, -4.4 and -5.0°C, where the temperature of -4.4°C was selected to highlight the differences in tolerance between acclimated and non-acclimated plants. In the patience tolerance study, Eucalyptus benthamii was the most tolerant clone, while the hybrid E. urophylla x E. grandis was the most susceptible. E. benthamii showed greater stomatal control, preserved photosynthetic rates and exhibited higher levels of soluble sugars and anthocyanins. In the patience tolerance induction study, it was possible to induce greater tolerance in E. urophylla x E. grandis, immediately after acclimatization, however concluding that the memory of the acclimatization caused is not persistent. The knowledge elucidated here can support management plans in areas at risk of complications, as well as guide geneticists and forestry professionals regarding the best crosses to be performed to result in more tolerant hybrids.

Keywords: low temperature; cold; eucalyptus; heat stress; survival; level of damage.

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