The circadian system of plants is a complex physiological mechanism, a biological process in which plants can adjust themselves according to the day and night cycle. To understand the effects of different photoperiods on the biological clock of tea plants, we analyzed the expression levels of core clock genes (CCA1, PRR9, TOC1, ELF4) and photosynthesis-related genes (Lhcb, RbcS, atpA) under normal light (light/dark = 12 h/12 h, 12L12D) and took the cost function defined by cycle and phase errors as the basic model parameter. In the continuous light environment (24 h light, 24L), the peak activity and cycle of key genes that control the biological clock and photosynthesis were delayed by 1–2 h. Under a skeleton photoperiod (6L6D, 3L3D), the expression profiles of clock genes and photosynthesis-related genes in tea plants were changed and stomatal opening showed a circadian rhythm. These observations suggest that a skeleton photoperiod may have an effect on the circadian rhythm, photosynthetic efficiency and stomatal regulation of tea plants. Our study and model analyzed the components of circadian rhythms under different photoperiodic pathways, and also revealed the underlying mechanisms of circadian regulation of photosynthesis in tea plants.

Celery (Apium graveolens L.) is a kind of green leaf vegetable with a large consumption demand in the food industry. It is a commonly used material in quick-frozen food stuffing such as dumplings and steamed stuffed. Fresh celery leaf blades and petioles are rich in photosynthetic pigments including chlorophyll and carotenoid, their contents are closely related to the quality of celery and its products. In order to explore the effects of freezing and thawing temperature and thawing time on the degradation of photosynthetic pigments in celery leaf blades and petioles, the changes in photosynthetic pigments during thawing storage were measured under different freezing and thawing temperatures. The results showed that lower freezing and thawing temperatures were beneficial to the preservation of photosynthetic pigments in celery leaf blades and petioles, and the loss of photosynthetic pigments enhanced with the increase in thawing temperature and thawing time. Under the cold storage condition of −80 °C, the loss rate of pigment substances can be reduced by nearly 20% compared with that of −18 °C, and −80 °C and 4 °C could be the best temperature combination of freezing and thawing. The content and degradation rate of photosynthetic pigments in celery leaf blades were higher than that in petioles during thawing, with a total chlorophyll loss rate reaching 35% during 6 to 12 h after thawing. The increase in temperature difference between freezing and thawing could aggravate the damage to the cell structure and the degradation of the pigment, as chlorophyll is more sensitive to temperature changes, and the degradation rate is significantly higher than that of carotenoids. From the perspective of delaying the degradation of photosynthetic pigments, the results of this study will provide potential references for the reasonable configuration of freezing and thawing temperatures in the process of storage and transportation of celery products.

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.

BRs (brassinosteroids), an endogenous hormone in plants, regulate cellulose accumulation, cell elongation and plant growth. Propiconazole (PCZ) is an effective inhibitor of BR biosynthesis. DCB (2,6-Dichlorobenzonitrile) can inhibit the synthesis of cellulose and affects the chemical composition of cell walls. Celery is one important leafy vegetable of the Apiaceae family with rich dietary fiber (including cellulose). The petioles length, leaf blades number and cellulose content determine the yield and quality of celery. The family members of AgCESAs are related to cellulose biosynthesis in higher plants. To investigate the effects of BRs, PCZ and DCB on the growth of celery, celery cv. ‘Jinnan Shiqin’ plants were treated with 24-epibrassinolide (24-EBL, most active form of BRs), PCZ and DCB, respectively. The results showed that exogenous application of BRs up-regulated the expression of AgCESAs genes and accumulated more cellulose in celery. The length of petioles and number of leaf blades in celery plants applied with exogenous BRs (1.24 × 10⁻⁶ mol/L 24-EBL) were increased 2.16 and 1.37 times of that in the control. The addition of PCZ inhibited the effects of exogenous BRs application. The lengths of hypocotyl and hypocotyl cells of celery plants treated with BRs were longer than that of the control. Under DCB treatments, the expression levels of AgCESAs genes in celery petioles and leaf blades were down-regulated compared with the control, and the celery plants showed decreased cellulose content, shorter petiole length and fewer leaf blades. The length of hypocotyl and hypocotyl cells of celery treated with DCB were shorter than that of the control. This study provided a reference for the functions of BRs and DCB on the growth and development of celery.

Tomato (Solanum lycopersicum L.) is one of the vegetables widely cultivated in the world, whose fruits are rich in nutrients. Soluble solids content (SSC) is one of the important factors affecting tomato fruit flavor and plays a decisive role in improving tomato quality. Molecular markers are genetic markers that reveal plant genetic polymorphism at the DNA level, which have the advantages of improving breeding purposes, increasing selection efficiency, and shortening breeding years. The molecular marker TGS0892 is located on chromosome 6 of the tomato genome and is closely related to soluble solids. In the present work, five different tomato cultivars were used as experimental materials. The results showed that ‘TD-10’ had the lightest single fruit weight and the highest soluble solids content, while ‘TD-8’ and ‘TD-9’ had heavier single fruit weight and lowered soluble solids content. Seventeen genes within 50 kb upstream and downstream of the molecular marker TGS0892 were identified using bioinformatics methods, and their structural analysis and functional annotation were performed. Quantitative reverse transcription PCR (RT-qPCR) showed that the expression levels of the 17 genes in different tomato cultivars were classified into two major categories, with the highest expression in ‘TD-7’ and other cultivars, respectively. Soly065970 and Soly066010 were significantly more expressed in high soluble solids tomato cultivars (‘TD-7’ and ‘TD-10’) and less expressed in the low soluble solids tomato cultivar (‘TD-9’). The results suggested that Soly065970 and Soly066010 may be involved in regulating the soluble solids metabolic process, which provides a reference for studying the formation mechanism of highly soluble solids in tomatoes.

Low temperature, as a kind of stress factor, often leads to tomato growth stagnation or yield reduction or even no harvest in production. At present, numerous genes have been shown to be involved in the regulation of cold resistance in the tomato. Complex regulatory mechanisms responding to low temperature stress in the tomato are still unclear in their details. In this study, six accessions of tomato (‘NL-7’, ‘NL-15’, ‘NL-18’, ‘NL-21, ‘NL-37’, and ‘NL-67’) with different cold tolerance were selected to detect the response to low temperature. The results showed that ‘NL-15’, ‘NL-18’, and ‘NL-21’ tomato accessions had cold tolerance under 8 °C/6 °C (day/night) for 15-day treatments. The TGS377 molecular marker, closely related to cold tolerance, was located on chromosome 1. The potential factors were identified and bioinformatics analysis within 50 kb upstream and downstream of TGS377. Fifteen genes were identified, and their structural analysis and functional annotation were also performed. The expression levels of Solyc01g008480 and Solyc01g150104 in the cold-sensitive tomato accessions (‘NL-7’, ‘NL-37’, and ‘NL-67’) were higher than that in the cold-tolerant accessions (‘NL-15’, ‘NL-18’ and ‘NL-21’). The expression levels of Solyc01g008390 and Solyc01g008410 in the cold-tolerant tomato ‘NL-18’ accession was significantly higher than that in the cold-sensitive accessions (‘NL-15’, ‘NL-18’, and ‘NL-21’). The results suggested that these genes may be involved in regulating low temperature response in the tomato, which lays a foundation for the search of potential cold response regulators in the tomato.