Low-intensity laser exposure enhances rice (Oryza sativa L.) growth through physio-biochemical regulation, transcriptional modulation, and microbiome alteration

Abstract

Environmental stressors significantly impact plant growth and agricultural productivity, necessitating innovative approaches to enhance crop resilience and yield. While high-intensity laser applications in agriculture have traditionally been limited to destructive purposes due to their harmful effects on plant growth, the emergence of low-intensity laser technology presents new opportunities for crop improvement. However, the molecular mechanisms underlying the beneficial effects of low-intensity laser treatment remain largely unexplored. This study investigated the effects of low-intensity laser treatment on rice seedling growth, physiological and molecular responses, and rhizosphere microbial communities. Low-intensity laser treatment (2 µmol/m²/s PPFD) significantly enhanced root and shoot growth, enhanced biomass accumulation, and improved yield parameters, with a 16.8% increase in effective panicles and 9.01% higher yield per plant. Physiological analyses revealed elevated antioxidant enzyme activities (POD and SOD) and reduced ROS levels in treated plants. Transmission electron microscopy showed improved chloroplast structure, correlating with enhanced photosynthetic efficiency. Transcriptomic analysis identified 623 differentially expressed genes, with significant enrichment in pathways related to photosynthesis, carbon metabolism, and hormone signaling. Notably upregulation was observed in photosynthesis-related genes (OsPsbB and OsCYF) and hormone signaling genes (OsWRKY114 and OsWRI1). Additionally, 16S rRNA sequencing revealed significant restructuring of rhizosphere bacterial communities in laser-treated plants, with enrichment of beneficial genera including Pseudomonas and Enterobacter. These findings establish low-intensity laser treatment as a promising tool for enhancing rice productivity through coordinated regulation of photosynthetic efficiency, stress responses, and beneficial microbiome interactions.

Keywords: Antioxidant enzymes; Laser; Microbiome; Photosynthesis ROS; Rice.

Fig. 1

Laser treatment promotes the growth of rice seedlings. (a) The representative images of rice seedlings growing under untreated (CK) and laser treatment (2 µmol/m²/s PPFD) conditions (Up: grown in a hydroponic box; Below: individual seedling photos). Bar = 5 cm. (b-c) Graph showing the stem length (b) and root length (c) of rice seedlings under laser treatment. (d-e) Graph showing the dry weight of stem (d) and root (e) under laser treatment. (f) Graph showing the root activity under laser treatment. (g) The representative image of laser treated and untreated (CK) rice plants at heading stage growing in pots. Bar = 10 cm. (h-l) Graph showing that number of effective tillers (h), yield (l), hundred grain weight (i), number of grains per panicle (j) and setting rate (k) under laser treatment. (m) The representative image shows the yield of each laser treated and untreated (CK) rice plant. Bar = 5 cm. Error bars represent ± SE. Asterisks indicate significant differences as tested by Student’s t-test (* p < 0.05, ** p < 0.01, *** p < 0.001)

Fig. 2

Effect of laser treatment (2 µmol/m²/s PPFD) on rice physiology. Graph showing (a) POD (b) SOD (c) MDA and (d) H₂O₂. Error bars represent ± SE. Asterisks indicate significant differences as tested by Student’s t-test (* p < 0.05, ** p < 0.01)

Fig. 3

Laser treatment (2 µmol/m²/s PPFD) promotes chloroplast development and photosynthesis profile of rice seedlings. (a) TEM images of chloroplasts from mesophyll cells of untreated leaves (CK) and under laser treatment leaves (Laser). (b-f) Graph showing SPAD value (b), net photosynthesis rate (c), transpiration rate (d) and stomatal conductance (e) of rice seedlings under laser treatment was higher than untreated plants, while intercellular carbon dioxide concentration (f) was lower than untreated plants. Error bars represent ± SE. Asterisks indicate significant differences as tested by Student’s t-test (* p < 0.05, ** p < 0.01, ****p < 0.0001)

Fig. 4

Laser treatment (2 µmol/m²/s PPFD) -induced transcriptomic changes in rice seedlings (a) Volcano plot showing differential gene expression analysis between laser treated and untreated rice plants, in which P value < 0.05 and show 144 up regulation genes, 479 down regulation genes. (b) Heatmap of clustering analysis of differentially expressed genes in laser treated leaves and untreated leaves. (c) Gene Ontology (GO) enrichment analysis of differentially expressed genes between laser treated and untreated rice plants. (d) KEGG pathway annotation of enriched pathways represented among the differential up regulation genes between laser treated and untreated rice plants. Arrows indicate the photosynthesis pathway

Fig. 5

Expression validation of the selected growth and photosynthesis-related DEGs in rice seedlings under laser treatment (2 µmol/m²/s PPFD). (a, b) photosynthesis pathways and (c, d) hormone pathways. Expression levels in CK plants were normalized to 1. Error bars represent ± SE. Asterisks indicate significant differences as tested by Student’s t-test (* p < 0.05, ** p < 0.01, *** p < 0.001, ****p < 0.0001)

Fig. 6

Effect of laser treatment (2 µmol/m²/s PPFD) on the rice rhizosphere bacterial community (a) Relative abundance (%) of top bacterial genus in each treatment. (b) Relative abundance (%) of top bacterial phylum in each treatment. Heatmap of clustering analysis of class (c) and genus (d) of the top 20 dominant bacterial community abundance