Plant spacing usually refers to distances between plants within and between rows in the field. Different spacing in crop planting would generally influence the size, plant architecture, economic productivity, etc. The present research provided a time course monitoring of stem development in tobacco with different plant spacing. The result showed that cambium activity, vascular bundle thickness, lignin, cellulose, and hemicellulose content, as well as the macronutrient deposition in the stem varied because of the different plant spacing. Furthermore, the genes (NtHB8s and NtNST3s) coding the homologs of HB8 and NST3 transcription factors, which are involved in plant secondary growth, were cloned in tobacco. In the time course, they also indicated diverse expression patterns among altered plant-spacing treatments. Their transcriptomic activities were validated, and the motifs that might bind transcription factors in their promoter regions were predicted. Promoters of NtHB8s and NtNST3s genes were rich in light-response elements; as a result, light might be the main environmental factor in plant spacing to regulate stem secondary growth.

Quinoa is a gluten-free food crop that contains all the essential amino acids and vitamins. The selection of proper housekeeping and tissue-specific genes is the crucial prerequisite for gene expression analysis using the common approach, real-time quantitative PCR (RT-qPCR). In this study, we identified 40 novel candidate housekeeping genes by the minimum transcript per million (TPM), coefficient of variation (CV) and maximum fold change (MFC) methods and 19 candidate tissue-specific genes by the co-expression network method based on an RNA-seq dataset that included 53 stem, leaf, flower and seed samples, as well as additional shoot and root samples under different stresses. The expression stability of 12 housekeeping and tissue-specific genes, as well as that of another two traditionally used housekeeping genes, was further evaluated using qPCR and ranked using NormFinder, BestKeeper and the comparative delta-Ct method. The results demonstrated that MIF, RGGA, VATE and UBA2B were ranked as the top four most stable candidate housekeeping genes. qPCR analysis also revealed three leaf-specific genes and five root-specific genes, but no stem-specific gene was identified. Gene Ontology (GO) enrichment analysis identified that housekeeping genes were mainly enriched in the small molecule metabolic process, organonitrogen compound metabolic process, NAD binding and ligase activity. In addition, tissue-specific genes are closely associated with the major functions of a specific tissue. Specifically, GO terms “photosynthesis” and “thylakoid” were most significantly overrepresented in candidate leaf-specific genes. The novel housekeeping and tissue-specific genes in our study will enable better normalization and quantification of transcript levels in quinoa.

During the process of flue-curing and processing, leaves from cash crops such as tea and tobacco frequently undergo a phenomenon of browning, leading to reduced quality and significant economic losses. Despite a variety of approaches developed to suppress browning, little is known about the role that flue-curing of postharvest leaves with stems plays in delaying browning. This study investigated the impact of leaf-with-stem (LWS) flue-curing on the browning of tobacco and its underlying mechanisms. Physiological results indicated that LWS flue-curing effectively delayed browning by enhancing antioxidant capacity and maintaining reactive oxygen species (ROS) levels during the yellowing stage. Comprehensive transcriptome and metabolome analyses showed that LWS flue-curing significantly influenced various metabolic pathways. Specifically, 196, 218, and 402 metabolites, and 65, 131, and 718 genes exhibited significant changes at the 38 °C, 40 °C, and 42 °C stages, respectively, inhibiting membrane lipid degradation and enhancing the supply of reducing hydrogen through the oxidative pentose-phosphate pathway. Additionally, hormone signaling pathways were found to be associated with LWS flue-curing. These findings highlight the complex interplay of metabolic pathways and signaling networks in attenuating browning, providing valuable insights for minimizing postharvest leaf browning during flue-curing and processing.

Light quality plays a crucial role in plant growth and development. Nevertheless, mechanistic insights regarding the effects of monochromatic red light and monochromatic blue light on the development of tobacco seedlings remain limited. This study aims to elucidate how monochromatic red and blue light specifically affect the growth of tobacco seedlings, with a focus on systemic nutrient allocation from roots. By analyzing morphological, physiological and transcriptomic changes in both shoots and roots, we aim to fill the gaps in our understanding of the interaction between light quality and nutrient absorption mechanisms. Physiological results indicated that red light promoted seedling growth and enhanced nitrogen (N)and potassium (K) uptake, whereas blue light exerted the opposite effect by inhibiting growth and reducing nutrient uptake. Transcriptome analysis revealed that genes related to N uptake (e.g., NRT1.1 was induced by red light and suppressed by blue light), N assimilation and K uptake were significantly regulated by monochromatic light in roots. Furthermore, various transcription factors (TFs) involved in phytohormone signal transduction were significantly regulated by blue and red light. These findings suggest that red and blue light may modulate phytohormone metabolism through TF–mediated pathways in tobacco roots. Overall, this study provides valuable insights into the effects of light quality on plant growth and underscores the importance of elucidating light-mediated mechanisms for improving crop yield and quality.

Tobacco (Nicotiana tabacum L.) leaf curing is a critical postharvest process that fundamentally determines the quality, aroma, and combustibility of the fi

Microplastic and heavy metal contaminants have attracted global concern due to their ubiquitous presence and long-lasting persistence, yet little is known about their interactions on plant growth performance. Here, different concentrations of polyethylene (PE)-microplastics (MPs) and lead (Pb) were applied to soils to investigate their impacts on tobacco plants. Our results showed that tobacco plants grown in PE-MP- and Pb-contaminated soils displayed a significant reduction in leaf pigment content, photosynthetic efficiency, and plant biomass, as well as a remarkable increase in the contents of hydrogen peroxide, superoxide ions, and malondialdehyde. The Pb contents in plant roots decreased from 886 mg kg-1 t o 7 65 mg kg-1 with increasing concentrations of PE-MPs, while the leaf Pb concentrations remained unaffected. The impaired photosynthetic performance in tobacco leaves was attributed to Pb stress, causing stomatal closure and PE-MP-induced nonstomatal limitation. Moreover, the coexistence of PE-MPs and Pb damaged the PSII reaction center, disturbed the electron transport process, and reduced photosynthetic efficiency. To alleviate oxidative damage, the contents of proline and soluble sugar, along with the antioxidant enzyme activities, underwent a significant increase in tobacco plants. This work offers valuable insights for addressing the challenges posed by the emergence of contaminants in agricultural production.