Ph.D., associate professor Belyakov M. V., student Kharitonova D.A.

The Branch of National Research University "Moscow Power Engineering Institute" in Smolensk, Russia

Research of galega orientalis seeds with luminescent methods during scarification

Before sowing the galega orientalis (fodder galega or eastern galega) seeds are scarified by breaching the integrity of the shell. Such superficial shell damage allows seeds to absorb water and swell better and also grow faster. Scarification can increase the germination rate from 10 to 90%, but it should be carried out not earlier than 3-4 weeks before sowing, because scarified seeds lose their germination quickly [1].

In this research we carried out measurements of excitation and luminescence spectra using the hardware-software complex consisting of multifunctional spectrofluorimeter "Fluorat-02-Panorama", a computer with installed «Panorama Pro» software and an external camera for the testing samples.

In the first experiment the mechanical scarification of 200 galega orientalis seeds was made with the sandpaper. Wherein the intensity of this scarification was different: 100 seeds were slightly scarified, 100 – strongly scarified.

The technique involved the following steps:

1. Preparation of the installation.

2. Visual analysis and seed samples selection.

3. The excitation spectrum measurement of unscarified seed.

4. The luminescence spectrum measurement of unscarified seed.

5. Seed scarification with sandpaper.

6. The excitation spectrum measurement of scarified seed.

7. The luminescence spectrum measurement of scarified seed.

8. Tracing and averaging of excitation and luminescence spectra and its general analysis (Fig. 1).

Fig.1. - The excitation and luminescence spectra of galega orientalis seeds: 3, 6 - unscarified; 2, 5 – slightly scarified; 1, 4 – strongly scarified

The germination results of galega orientalis were obtained and placed in Table 1. Besides, for the mathematical processing in «PanoramaPro» integrals under the curves of excitation and luminescence and their average value were calculated (Table. 1). The integral under the curve of the luminescence spectrum has the physical meaning of the luminescence flux. The integrals under the curves of excitation were calculated for the two parts of the spectrum: 380-475 nm, and 475-505 nm to determine the relationship between the humps.

Table 1

Luminescent specification of galega orientalis seeds of different germination

Scarification	Germination, %	Excitation		Luminescence
		Нav., pu		Фav., pu
		380-475	475-505
Strong	100	1202	212	1282
Slight	97	680	292	1194
Absence	82	340	165	833

Operating range of the excitation spectrum: 380-505 nm; the major maximum at unscarified and slightly scarified seeds is 461 nm, while strongly scarified seeds have two major peaks: 450 and 460 nm; supplementary peak of all three: 485 nm. Also strongly scarified seeds have additional supplementary peak at a wavelength of 425 nm. Operating range of the luminescence spectrum: 480-630 nm. Curve of luminescence spectrum reaches a maximum in the range from 527 nm to 535 nm. And, for strongly scarified seeds that range is displaced to the left: 520-530 nm.

In addition, the Figure 1 shows that due to the scarification maximum η_e of bimodal excitation spectrum has increased with respect to the excitation spectrum of unscarified seed: for slightly scarified by 32% and for strongly scarified by 34%. The position of the maxima in the spectra of unscarified and slightly scarified seeds has not changed, but the ratio of their intensity has changed: at unscarified the intensity of the first maximum is 0.9 pu greater than the second maximum, and at slightly scarified - 2 pu. If we take the two main peaks of strongly scarified seeds as a one, the ratio of their intensity maxima differs by 3.1 pu. Change of the intensity of the luminescence spectrum is similar to the change of the excitation spectrum: intensity increased by 32 and 34%, respectively.

In the second experiment we carried out the time dependent research of luminescent specifications of 30 galega orientalis seeds during scarification. We measured: excitation and luminescence spectra of unscarified seeds, spectra measured immediately after the scarification, spectra measured one day after the scarification and 7 days after the scarification. Moreover, tracing and averaging of excitation and luminescence spectra was made (Figure 2).

Fig.2. - The excitation and luminescence spectra of galega orientalis seeds: 4, 8 - unscarified; 3, 7 - measured immediately after the scarification; 2, 6 - measured one day after scarification; 1, 5 - measured 7 days after scarification

We obtained the germination results of galega orientalis and placed them in Table 2. Integrals under the curves of excitation and luminescence and their average value were calculated (Table 2).

Table 2

Luminescent specification of galega orientalis seeds of different germination seeds depending on the time after scarification

Seeds	Germination, %	Excitation	Luminescence
		Нav., pu	Фav., pu
Unscarified	82	362	724
Measured immediately after the scarification	90	556	1056
Measured one day after scarification	100	808	1362
Measured 7 days after scarification	100	896	1590

Operating range of the excitation spectrum: 420-505 nm; the major maximum at unscarified, measured immediately after the scarification and one day after the scarification - 460nm, while measured after 7 days - 461 nm. Operating range of the luminescence spectrum: 480-630 nm. Curve of luminescence spectrum reaches a maximum in the range from 527 nm to 535 nm. And, for the seeds measured after 7 days that range is displaced to the left.

Figure 2 and Table 2 shows that after scarification relative luminescence flux continues to grow: in a day – by 29%, after 7 days - by 16.7% more from the previous measurement. Hence, it is recommended to make scarification a week before the sowing.

In the third experiment the kinetic specifications of luminescence were measured. The scanning of five unscarified and scarified galega orientalis seeds was held by duration and by delay (Fig. 3). Measurements were carried out by delay at τ_dur = 4.45μs and by duration at τ_del = 0.75 μs, λ_e = 534 nm, λ_r = 461 nm (previously obtained by measurement of the excitation and luminescence spectra).

Fig.3. - The results of the kinetic specifications of luminescence measurements of galega orientalis seeds: 4, 2 – unscarified by delay (4) and duration (2); 3, 1 - scarified by delay (3) and duration (1)

Measuring the of galega orientalis seeds’ kinetics of growth, we find out that up to 0.4 μs signal is very small, then begins to rise sharply to 2.6 μs, then grows more slowly and from 4.0 μs almost unchangeable.

Measuring the of galega orientalis seeds’ kinetics of decay, we obtained that the signal is maximum from 1.2 to 2.0 μs.

References:

1. Vozdelyvanie kormovyh kul'tur. Galega vostochnaya. Podgotovka semyan k sevu, posev [Digital resource]. – Access mode: http://agrobelarus.ru/content/podgotovka-semyan-posev-galegi-vostochnoy. Date of application: 12.02.2016.