Influence of the Duration of Microwave Irradiation of Scots Pine (Pinus sylvestris L.) Cones on the Quality of Harvested Seeds

Abstract

To improve the process of seed extraction, new solutions have been investigated in an attempt to develop guidelines for the construction of small seed extraction equipment. One of the solutions proposed in this field is the use of electromagnetic radiation in the first stage of hulling cones, reducing their initial moisture content, which will result in quicker scale opening. It is proposed that cones should be irradiated for a relatively short period in the first stage. This operation will allow a quicker loss of moisture from the cones that are still closed, which will result in a more intensive opening of cone scales and will also positively affect the exposure of seeds for the next phase of hulling. The aim of the study was to evaluate the effect of microwave irradiation of pine cones on the quality of the seeds obtained. Cones were exposed to microwaves produced by an 800 W generator. The research was performed in several modes, in which the variable parameters were the duration of microwave irradiation, arrangement of cones with the apex pointed towards either the inner or outer part of the turntable, and the number of cones. The temperature distribution on the surface of and inside the cones was determined using the THERM v2 (Vigo System SA, Ożarów Mazowiecki, Poland) thermal image processing software. We also assessed the energy (vitality) and germinability (quality class) of seeds that were not exposed and those after microwave treatment. The results of the research allowed us to state that, with the assumed parameters of the process, it is possible to obtain second quality class seeds after exposure to microwaves for 5 s. This result was comparable to the quality of seeds obtained without the use of microwaves. When the irradiation time was increased above 5 s, the vitality of seeds decreased and their quality was not satisfactory.

Effect of Seed Extraction Period and Germination Temperature on Viability of Pinus patula Under Controlled Conditions

“…The results of this study showed that germination rates decline with increase in exposure period within the three phases of extraction. Earlier studies by [24] showed that exposure to higher seed extraction temperatures negatively influence germination of pine seeds.…”

“…Higher temperature intensities (a function of the temperature reached and the time of exposure) has been shown to be a key factor in cone opening for seed release and also influences seed germination energy, rate and capacity [23][24][25][26]. Heat tolerance and thermal shock resistance as indicated by germination energy is shown to be dependent on species, cone and seed moisture content [10][11][12].…”

Conifer Biotechnology: An Overview

“…The seeds have great importance at this point. In this regard, experiments in Pinus sylvestrys have been carried out to evaluate the effect of humidity reduction on the quality of seeds obtained from cones in order to observe a faster and more intensive scale opening of cone scales [23]. Research has also been initiated on the performance of seedlings from color-sorted seeds of Scots pine [24].…”

The cracking of Scots pine (Pinus sylvestris) cones

“…However, to our knowledge, the initial opening event of a cone has not been documented from a biomechanical viewpoint in detail until now. A study by Aniszewska et al (2019) has shown that short microwave irradiation of initially closed Scots pine cones leads to their opening due to the rapid loss of moisture, and that viable seeds can be harvested from them. The process of initial opening is ecologically relevant, as it influences the dispersal of the mostly airborne seeds and, ultimately, the survival rate of seedlings (Winsa, 1995;Przybylski et al, 2021).…”

“…However, to our knowledge, the initial opening event of a cone has not been documented from a biomechanical viewpoint in detail until now. A study by Aniszewska et al. (2019) has shown that short microwave irradiation of initially closed Scots pine cones leads to their opening due to the rapid loss of moisture, and that viable seeds can be harvested from them.…”