Celery is an important leaf vegetable crop in Apiaceae, of which the petiole and leaf blade are the main edible parts. The content and proportion of photosynthetic pigments, mainly chlorophyll, have an important effect on the growth and quality of celery. As a brassinosteroid (BR) plant hormone with high physiological activity, 24-epibrassinolide (24-EBL) has the physiological functions of promoting chlorophyll accumulation and delaying leaf senescence. To investigate the effects of 24-EBL treatment on chlorophyll accumulation at different growth stages of celery, celery plants (variety Ningqin NO. 1) were treated from 45~59 days after sowing (DAS), at intervals of 7 days, with two different concentrations of 24-EBL: 1.04 × 10⁻⁶ mol·L⁻¹ and 1.67 × 10⁻⁶ mol·L⁻¹. The content of chlorophyll and the expression levels of genes related to its metabolism were determined in celery leaf blades and petioles at three different stages (52, 59, 66 DAS). In the first stage (52 DAS), 1.04 × 10⁻⁶ mol·L⁻¹ treatment of 24-EBL increased the expression levels of genes related to chlorophyll biosynthesis (AgHEML, AgCHLG, and AgCAO) to promote the accumulation of chlorophyll in leaf blades. During the second and third stages (59 and 66 DAS, respectively), 1.67 × 10⁻⁶ mol·L⁻¹ 24-EBL treatment induced the expression levels of genes related to chlorophyll cyclic regeneration (AgCLH) and inhibited the up-regulation of genes related to chlorophyll degradation (AgNYC, AgHCAR, and AgPPH) to promote chlorophyll (especially chlorophyll b) accumulation. These treatments regulated the ratio of chlorophyll a content to chlorophyll b content and changed the leaf color of the celery. The results show that leaf spraying with an appropriate concentration of 24-EBL can facilitate chlorophyll synthesis by promoting chlorophyll synthesis and cycling-related gene expression levels and increase chlorophyll content in the leaves of celery. This study provides a reference for exploring the specific function of 24-EBL in regulating chlorophyll content during the growth and development of celery.

Carrot (Daucus carota L.) is an important root vegetable crop in the Apiaceae and is widely cultivated around the world. Expansins play crucial roles in the growth and development of plants. Here, a total of 35 carrot expansins were identified from carrot. Sequence alignment and phylogenetic analysis revealed that carrot expansins could be classified into four subfamilies, each with similar exon/intron structures and motif compositions, indicating that carrot expansins were relatively conserved during evolution. Chromosomal localization and gene duplication analysis indicated that DcEXP genes were unevenly distributed across carrot nine chromosomes and had evolved predominantly under purifying selection. Measurements of key agronomic characters of carrots at different developmental stages (30, 60, and 90 days after sowing) indicated significant positive correlations among root fresh weight, aboveground fresh weight, root–shoot ratio, root length, and root diameter. The period from 30 to 60 days after sowing was identified as the primary phase of taproot enlargement. Analysis of spatiotemporal expression patterns revealed that most DcEXP genes were specifically expressed in the taproots, and only one gene, DcEXP18, was specifically expressed in leaves. During the rapid growth period of carrot taproots (30 and 60 days after sowing), the genes DcEXP2, DcEXP3, DcEXP5, DcEXP8, DcEXP11, DcEXP13, DcEXP17, DcEXP19, DcEXP20, DcEXP22, DcEXP26, DcEXP28, and DcEXP33 exhibited high expression levels, suggesting that they played potential important roles in carrot taproot enlargement. These findings will advance our knowledge of the molecular mechanisms underlying expansin regulation of carrot growth and development.