Abstract
The objectives of this work were to analyze seed behaviour under controlled deterioration and estimate viability equations for forest species Eucalyptus grandis and Pinus taeda. Desired moisture content levels were achieved from initial values after either rehydration over water or drying over silica gel, both at 25 ºC. Seed sub samples with 8 moisture contents each for E. grandis (1.2 to 18.1%, initial value of 11.3%) and P. taeda (1.5 to 19.5%, initial value of 12.9%) were sealed in laminate aluminium-foil packets and stored in incubators maintained at 40, 50 and 65 ºC. The seeds from these species exhibited true orthodox and sub-orthodox storage behaviour, respectively, however E. grandis showed higher seed storability, probably due to a different seed chemical composition. Lowest moisture content limits estimated for application of the viability equations at 65 ºC were 4.9 and 4.1 mc for E. grandis and P. taeda, on equilibrium with ±20% RH. The viability equation estimated quantified the response of seed longevity to storage environment well with K E = 9.661 and 8.838; C W = 6.467 and 5.981; C H = 0.03498 and 0.10340; C Q = 0.0002330 and 0.0005476, for E. grandis and P. taeda, respectively.
Highlights
Eucalyptus spp. and Pinus spp. are the main sources for supplying raw material for the production of short and long fiber cellulose and mechanical processing and have been established around 3,800,000 ha of brazilian reforested areas.Seed storability is affected mainly by moisture content and storage temperature (T)
The orthodox seed behavior can be investigated thereby reducing both moisture content and temperature, and their longevity can be described in a quantifiable and predictable way Bonner (1990) proposed a specific classification for forest species: true orthodox, which tolerates desiccation at low T and maintains seed viability for long periods in dry conditions (Eucalyptus, Pinus and Acacia); sub-orthodox, which could be stored in the same conditions above for the maximum of 6 years, presenting high lipid content, small size and fine seed coats; recalcitrant temperate, which are sensitive to desiccation but could be stored at T around freezing (Quercus spp.) and recalcitrant tropical, presenting big seeds and being sensitive to desiccation and freezing
Extraction relationship or fruit / seed relationship is the amount of capsules required to produce one kg of mixed seeds and presented a medium rate of 15:1 for E. grandis
Summary
Eucalyptus spp. and Pinus spp. are the main sources for supplying raw material for the production of short and long fiber cellulose and mechanical processing and have been established around 3,800,000 ha of brazilian reforested areas.Seed storability is affected mainly by moisture content (mc) and storage temperature (T). The orthodox seed behavior can be investigated thereby reducing both moisture content and temperature, and their longevity can be described in a quantifiable and predictable way Bonner (1990) proposed a specific classification for forest species: true orthodox, which tolerates desiccation at low T and maintains seed viability for long periods in dry conditions (Eucalyptus, Pinus and Acacia); sub-orthodox, which could be stored in the same conditions above for the maximum of 6 years, presenting high lipid content, small size and fine seed coats; recalcitrant temperate, which are sensitive to desiccation but could be stored at T around freezing (Quercus spp.) and recalcitrant tropical, presenting big seeds and being sensitive to desiccation and freezing (coconut, cocoa and mango).
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