In the present study, the effects of nitrogen (N) supply on water uptake, drought resistance, and hormone regulation were investigated in Populus simonii seedlings grown in hydroponic solution with 5% polyethylene glycol (PEG)-induced drought stress. While acclimating to drought, the P. simonii seedlings exhibited a reduction in growth; differential expression levels of aquaporins (AQPs); activation of auxin (IAA) and abscisic acid (ABA) signaling pathways; a decrease in the net photosynthetic rate and transpiration rate; and an increase in stable nitrogen isotope composition (δ¹⁵N), total soluble substances, and intrinsic water use efficiency (WUEi), with a shift in the homeostasis of reactive oxygen species (ROS) production and scavenging. A low N supply (0.01 mM NH₄NO₃) or sufficient N supply (1 mM NH₄NO₃) exhibited distinct morphological, physiological, and transcriptional responses during acclimation to drought, primarily due to strong responses in the transcriptional regulation of genes encoding AQPs; higher soluble phenolics, total N concentrations, and ROS scavenging; and lower transpiration rates, IAA content, ABA content, and ROS accumulation with a sufficient N supply. P. simonii can differentially manage water uptake and hormone modulation in response to drought stress under deficient and sufficient N conditions. These results suggested that increased N may contribute to drought tolerance by decreasing the transpiration rate and O₂⁻ production while increasing water uptake and antioxidant enzyme activity.

Lupinus polyphyllus is rich in color, making it a well-known horticultural ornamental plant. However, little is known about the genes related to anthocyanin and carotenoid biosynthesis in L. polyphyllus. In this study, transcriptome sequencing was performed on eight different colors of L. polyphyllus. A total of 1.13 billion clean reads were obtained and assembled into 89,124 unigenes, which were then aligned with six databases, resulting in the identification of 54,823 annotated unigenes. Among these unigenes, 76 and 101 were involved in the biosynthetic pathway of carotenoids and anthocyanins, respectively. In addition, 505 transcription factors were revealed, which belonged to the MYB, R2R3-MYB, NAC, bHLH, and WD40 families. A total of 6,700 differentially expressed genes (DEGs) were obtained by comparative transcriptome analysis. Among them, 17 candidate unigenes (four carotenoid genes, seven anthocyanin genes, and six TFs) were specifically up-regulated for one or more colors of L. polyphyllus. Eight representative candidate unigenes were analyzed by qRT-PCR. The findings enrich the transcriptome database of lupine, and provide a rich molecular resource for research on the coloration mechanism of L. polyphyllus.

The poplar is a model system for research on wood plant biology. An establishment of an efficient poplar regeneration system (PRS) plays a key role in the molecular breeding of wood plants. At present, most established PRSs are based on orthogonal experiments of previous research data. However, such an experiment is complex, time-consuming, and inefficient for various poplar subspecies. Therefore, an efficient solution to the establishment of PRSs is urgent. In this study, the triploid white poplar (Populus tomentosa ‘YiXianCiZhu B385′) was used as an experimental material to establish a leaf-based regeneration system. Firstly, different concentrations of hormones were added into the medium for the differentiation, stretching, and rooting of leaves, and the electrical conductivity of the medium was measured by a conductivity meter. Secondly, the optimal hormone concentrations for differentiation, stretching, and rooting were obtained by wavelet analysis. Finally, the Electrical Signal Conduction Characterization Model (ESCCM) of different hormone concentrations in the differentiation, stretching, and rooting of poplars was established. The result showed that the ESCCM improves the efficiency of PRSs, and this provides new insight and theory in molecular breeding. The ESCCM also provides the possibility of an automated establishment of a PRS.