A study on the mechanical strength of alfalfa seeds stimulated with continuous laser light.

The presented study explored the impact of He-Ne laser light stimulation on basic, selected mechanical properties of alfalfa seeds. The following parameters were considered: destructive force (F), destructive force work (W), and absolute longitudinal deformation (dL). Moreover, the single seed mass (m) was measured prior to the compression test, and the ratios of destructive force to absolute longitudinal deformation (F/dL) and destructive force work to single seed mass (W/m) were calculated. Subsequently, the mass of 1000 seeds was determined using RADWAG XA110.3Y scales, and the geometric dimensions of seeds were measured using a Keyence VHX-2000 microscope. Prior to the compression test, the seeds were subjected to laser light stimulation (λ = 632.8 nm, surface force density = 6 mW·cm) with the exposure time of, respectively: 0 s (control - no stimulation - C), 30 s (L30s), 1 min (L1), 2 min (L2), and 3 min (L3). We observed an increase in most of the mechanical parameters measured under the influence of all the laser light stimulation variants. The only exception was the F/dL ratio, which decreased after 2 and 3-minute exposure, as compared to the control. The results evidenced increased mechanical strength of the stimulated seeds, which may prove significant to the cultivation of new, more resilient cultivars.