Spectroscopic Investigation of Tomato Seed Germination Stimulated by Trichoderma spp.

Seed germination is a complex process that can be negatively affected by numerous stresses. <i>Trichoderma</i> spp. are known as effective biocontrol agents as well as plant growth and germination stimulators. However, understanding of the early interactions between seeds and <i>Trichoderma</i> spp. remains limited. In the present paper, Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to reveal the nature of tomato seed germination as stimulated by <i>Trichoderma</i>. A rapid response of tomato seeds to <i>Trichoderma</i> spp. was observed within 48 h on Murashige and Skoog medium (MS) substrate, preceding any physical contact. Raman analysis indicated that both <i>Trichoderma</i> species stimulated phenolic compound synthesis by triggering plant-specific responses in seed radicles. The impact of <i>T. harzianum</i> and <i>T. brevicompactum</i> on two tomato cultivars resulted in alterations to the middle lamella pectin, cellulose, and xyloglucan in the primary cell wall. The Raman spectra indicated increased xylan content in NA with T9 treatment as well as increased hemicelluloses in GZ with T4 treatment. Moreover, T4 treatment resulted in elevated conjugated aldehydes in lignin in GZ, whereas the trend was reversed in NA. Additionally, FTIR analysis revealed significant changes in total protein levels in <i>Trichoderma</i> spp.-treated tomato seed radicles, with simultaneous decreases in pectin and/or xyloglucan. Our results indicate that two complementary spectroscopic methods, FTIR and Raman spectroscopy, can give valuable information on rapid changes in the plant cell wall structure of tomato radicles during germination stimulated by <i>Trichoderma</i> spp.