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Introduction Mitogenetic effect in Yeast cell Supe from Soya seeds: Spectral distribution and  temperature dependence Conclusions References

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SUPE in the visible and near ultraviolet range from germinating soya seeds has been measured [3].

The measured sample was prepared by putting 15 green soya seed (glycine max) over three dishes of filter paper in a plastic cuvette of 50 mm diameter; at the measurement starting the paper was imbued with 4 cc water.

The SUPE relative to two sets of samples is reported in fig. 3: i) seeds alive, whose germinability is higher than 99 %; ii) seeds devitalized by thermal processing for 30 min at 83 °C, whose germinability is zero. In the same figure it is reported also the corresponding mass increase; sample emission is relative to the sample mass measured at the same time

Fig. 3 - Seeds total emission and mass increase vs the elapsed time from the beginning of the imbibition.

From fig.3 the different behavior between living and devitalized seeds results evident; alive seeds start from a very low emission intensity, reach a maximum intensity 30 times larger after 4 hours and fall to a constant value during the homeostatic growth phase; devitalized seeds instead start with an higher emission rate at zero time which increases only by a factor two at the maximum, returning then to the starting value.

The spectral analysis reported in fig. 4 confirms the general features already found in total emissivity shown in Fig. 3, and it gives further information; the UV contributions, lying in the range of the filters centered at 220 nm, are relevant in living seeds and give a peak which corresponds to that occurring in the total emission; the red component centered at 650 nm, which rises fast, decreases instead quite slowly; the central visible component starts late after the initial phase and increases slowly at long times.

Fig. 4 - Seeds spectral emission for three different wavelengths vs the elapsed time from the beginning of the imbibition.

The different behavior of living seeds with respect to the devitalized ones is better evidenced by the time dependence of the two extreme components of the spectrum (220 and 650 nm). Fig.5 reports the yield ratio between the living seeds emission and that of devitalized ones. At the start time the red component for living seeds is less than for dead seeds. On the contrary the u.v. component at the maximum emission time is higher by a factor 6 for living seeds with respect to denatured ones.

Fig. 5 - Time dependence of the ratio of the spectral components of live and devitalized seeds.

In order to study the temperature dependence [4] of the biological and physical parameters connected to the seed germination, three different types of measurements were performed, at four different temperatures: the germinability, the weight increase and the intensity of the low level radiation emitted during the imbibition and germination. The following parameters were then calculated:

i) the photon count, referred to time unity and to the actual weight of the seeds during emission .

ii) the derivative with respect to the time of the weight increase during imbibition, referred to the actual weight .

iii) the derivative with respect to the time of the percentage of germinated seeds.

The trend versus time of the above parameters had in common the shape, i.e. they showed a maximum at a definite time elapsed from the beginning of the imbibition and this maximum was shifted to shorter times, versus the temperature increase.

Fig. 6 - t parameters relative to germination and imbibition versus t.emi relative to the spontaneous photon emission.

To study the dependence of the above quantities on temperature, it has been defined the parameters tger, timb and temi as the time relative to the maximum yield of germination, imbibition and emission respectively, for each temperature and for alive and devitalized seeds. These parameters are reported in fig. 6, where the following linear relation between tger and temi is shown:

tger = 1.8 x temi + 2.2

The additive factor 2.22 is attributed to the method adopted to measure the germination time which is detected by the protrusion of the radicle through the tegumentum. This method certainly caused a valuation delayed with respect to the starting time of the germination process. The delay introduced by the germination measuring method is then assumed to be equal to 2.2 hours.

Fig. 7 - Arrhenius plot of the rate V relative to photon emission, germination and imbibition for live and devitalized seeds.

In fig. 6 the timb values relative to the imbibition of devitalized seeds vs the corresponding temi relative to the different temperatures are reported. The trend of timb for live and for devitalized seeds seems to be the same.

The inverse of t parameter may be assumed as index of the rate v of the biological processes whose macroscopic effects are measured in terms of ultraweak photon emission, mass increase and germination.

The Arrhenius plot of this rate is shown in fig. 7 for live and devitalized seeds; on the x-scale the inverse of the absolute temperature at which the biological processes have been analyzed is reported; as regards the tger , the measured values have been attributed less the above quantity 2.2.

The slopes of the above curves, that give the activation energy of the corresponding processes, demonstrate that, for the live seeds, the emission of photons and germination has a common basis, as it regards, at least, the activation energy of the two processes (51 KJ/mole), while the imbibition rate of the live seeds is different.

As it regards the devitalized seeds, the activation energy of the photon emission is different from the one relative to the live seeds and it is almost equal to the one relative to the imbibition of the devitalized seeds.

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