The engineering of carbon nanotubes in the last decades resulted in a variety of applications in electronics, electrochemistry, and biomedicine. A number of reports also evidenced their valuable application in agriculture as plant growth regulators and nanocarriers. In this work, we explored the effect of seed priming with single-walled carbon nanotubes grafted with Pluronic P85 polymer (denoted P85-SWCNT) on Pisum sativum (var. RAN-1) seed germination, early stages of plant development, leaf anatomy, and photosynthetic efficiency. We evaluated the observed effects in relation to hydro- (control) and P85-primed seeds. Our data clearly revealed that seed priming with P85-SWCNT is safe for the plant since it does not impair the seed germination, plant development, leaf anatomy, biomass, and photosynthetic activity, and even increases the amount of photochemically active photosystem II centers in a concentration-dependent manner. Only 300 mg/L concentration exerts an adverse effect on those parameters. The P85 polymer, however, was found to exhibit a number of negative effects on plant growth (i.e., root length, leaf anatomy, biomass accumulation and photoprotection capability), most probably related to the unfavorable interaction of P85 unimers with plant membranes. Our findings substantiate the future exploration and exploitation of P85-SWCNT as nanocarriers of specific substances promoting not only plant growth at optimal conditions but also better plant performance under a variety of environmental stresses.

Nanotechnology is rapidly advancing towards the development of applications for sustainable plant growth and photosynthesis optimization. The nanomaterial/plant interaction has been intensively investigated; however, there is still a gap in knowledge regarding their effect on crop seed development and photosynthetic performance. In the present work, we apply a priming procedure with 10 and 50 mg/L Pluronic-P85-grafted single-walled carbon nanotubes (P85-SWCNT) on garden pea seeds and examine the germination, development, and photosynthetic activity of young seedlings grown on soil substrate. The applied treatments result in a distorted topology of the seed surface and suppressed (by 10–19%) shoot emergence. No priming-induced alterations in the structural and functional features of the photosynthetic apparatus in 14-day-old plants are found. However, photosynthetic gas exchange measurements reveal reduced stomatal conductance (by up to 15%) and increased intrinsic water use efficiency (by 12–15%), as compared to hydro-primed variants, suggesting the better ability of plants to cope with drought stress—an assumption that needs further verification. Our study prompts further research on the stomatal behavior and dark reactions of photosynthesis in order to gain new insights into the effect of carbon nanotubes on plant performance.

Clinoptilolite, with its structural peculiarities (ion-exchange and adsorbent properties), is an excellent candidate for direct use and various modifications. In this study, we explored the effect of ion exchange and the particle size of clinoptilolite on Raphanus sativus seed germination, plant growth, physiological and biochemical characteristics of plants. Plants were grown, for three consecutive runs, on non-modified clinoptilolite, 0.9–2.5 mm (C-2.5) and 2.5–5.0 mm (C-5.0); clinoptilolite fractions modified with ion exchange with ammonium (C_NH4-2.5 and C_NH4-5.0); and potassium (C_K-2.5 and C_K-5.0) ions. Our data revealed that ion exchange with ammonium increased water-holding capacity, while potassium exchange decreased the water-holding capacity of the substrates irrespective of their particle size. The positive effect of small fractions ion-exchanged clinoptilolite (C_NH4-2.5 and C_K-2.5) on seed germination, during the third run, was established. The small clinoptilolite fractions favored root crop production, particularly in C_K-2.5 plants only during the first run. Substantial positive effect on the content of total carbohydrates and polyphenols especially during the third run was established in plants grown on potassium-exchanged clinoptilolite. Our findings support the future exploration of clinoptilolite as a suitable substrate for plant growth in space and ground-based facilities for space-oriented experiments.

Low-molecular-weight chitosan derivatives emerged as promising plant growth biostimulants due to their favorable properties, such as biocompatibility, antibacterial and antifungal activity, enhancement of stress resistance, and yield improvement. In the present study, we evaluated the effect of pea seed priming with two types of chitooligosaccarides (aminochitooligosaccaride and chitooligosaccaride hydrochloride) applied at concentrations of 100 and 500 mg/L under non-stress conditions and 50 mM chronic NaCl stress. We characterized the seed surface topology by atomic force microscopy, the germination process by evaluation of seed germinability and synchrony, root emergence, seed imbibition capacity and ion leakage. Early plant growth and physiological performance were further evaluated in 14-day-old seedlings by measuring leaf water potential, Na⁺ accumulation in roots and leaves, photosystem II activity, leaf pigment content, and membrane stability. The results revealed changes in seed coat topology, i.e., higher surface roughness in 100 and 500 mg/L chitooligosaccaride hydrochloride and 500 mg/L aminochitooligosaccaride primed variants. Concentration-dependent effects of the two chitooligosaccarides under both non-stress and salt stress conditions were evident in 14-day-old seedlings. Under chronic salt stress, seed priming with 100 mg/L chitooligosaccharide hydrochloride and 500 mg/L aminochitooligosaccharide produced the most pronounced improvements in the primary photochemical reactions of photosynthesis, particularly the performance index on an absorption basis and the total performance index. Moreover, the investigated chitooligosaccharide, particularly chitooligosaccaride hydrochloride, preserved membrane integrity and maintained flavonol and anthocyanin levels, indicating a strong protective effect against salt stress. Overall, the data indicate beneficial effects on pea physiological status following seed priming with chitooligosaccarides under chronic salt stress conditions. This highlights the approach as a promising strategy for enhancing plant resilience in challenging environments, and it is worth further investigation and verification at the whole-plant level.