Manipulating the Difference between the Day and Night Temperatures Can Enhance the Quality of Astragalus membranaceus and Codonopsis lanceolata Plug Seedlings

Abstract

Astragalus membranaceus Bunge and Codonopsis lanceolata Benth. et Hook. f. are two famous medical species in Korea, China, and Japan, mainly used for treating diseases including cancer, obesity, and inflammation. Manipulation of the difference between the day and night temperatures (DIF) is an efficient horticultural practice to regulate the growth and development of vegetables in a glasshouse. However, little research has focused on how the DIF influences the plug seedling quality of medicinal plants. In this study, uniform plug seedlings were cultivated in three environmentally controlled chambers under an average daily temperature of 20 °C with negative (−10 °C), zero, or positive (+10 °C) DIFs, and the same relative humidity (75%), photoperiod (12 h), and light intensity (150 μmol·m−2·s−1 photosynthetic photon flux density with white LEDs). The results showed that the DIF had a noticeable effect on the growth, development, and morphology of A. membranaceus and C. lanceolata plug seedlings. The positive DIF (+10 °C) significantly increased the biomass (shoot, root, and leaf), stem diameter, and Dickson’s quality index, indicating an enhanced plug seedling quality. Moreover, the contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids, were higher with higher DIFs, where the maximum values were found at 0 °C or +10 °C DIF. Furthermore, the increases in the chlorophyll content and stomatal conductance were obtained in a positive DIF, indicating that a positive DIF was favorable to photosynthesis. An analysis of the gene expression showed that a positive DIF (+10 °C) up-regulated the expression of photosynthetic genes, including GBSS, RBCL, and FDX. In conclusion, the results of this study recommend a positive DIF (+10 °C) for enhancing the quality of A. membranaceus and C. lanceolata plug seedlings.

Lighting Direction Affects Leaf Morphology, Stomatal Characteristics, and Physiology of Head Lettuce (Lactuca sativa L.)

“…Chlorophyll, an essential component of the light-harvesting complex, plays a crucial role in capturing and transferring photons to the reaction center of the photosystem in the primary reaction [ 29 ]. The chlorophyll can be degraded by abiotic or biotic stresses such as heat, chilling, and drought [ 30 , 31 , 32 ].…”

Time Lag Between Light and Heat Diurnal Cycles Modulates CIRCADIAN CLOCK ASSOCIATION 1 Rhythm and Growth in Arabidopsis thaliana

“…Based on our results, the effects of DIF regulation on growth were predictable ( Figure 7 ). This prediction method in conjunction with specific growing conditions and/or crop species might be important for practical application in horticulture ( Kläring and Schmidt, 2017 ; Liu et al, 2019 ). However, as a limitation of this, other situations such as the 12/12 h temperature cycles were not addressed in this study, and further studies are required to determine the growth regulation of DIF.…”

Plant Agronomic Features Can Predict Quality and Field Performance: A Bibliometric Analysis

“…In turn, Liu et al [61] have mentioned that enrichment with CO 2 (1050 µmol mol −1 CO 2 ) and supplementary lighting (100 µmol m −2 s −1 ) can improve the quality of plants, by promoting a higher photosynthetic activity and increasing their total carbohydrate content. Similarly, Liu et al [96] have reported that DIFs of 0 • C or >10 • C substantially increase the content of primary and secondary metabolites in A. membranaceus and C. lanceolata seedlings. In addition, Liu et al [97] found that the physiological quality of different medicinal species improves at a night temperature of 15 • C due to an increase in CO 2 assimilation and in the synthesis of carbohydrates, including soluble sugars, starch, total phenols, and flavonoids.…”

“…The SDM/H ratio has been used to predict plant quality in different medicinal species [96,97] and in horticultural crops [6]. Recently, Bantis et al [5] evaluated different quantitative criteria for producing quality plants and found that the SDM/H ratio is one of the best indicators for predicting the physiological and commercial quality of watermelon and interspecific squash seedlings.…”

“…The Root Dry Matter/Root Length (RDW/RL) ratio (g cm −1 ) is considered a root quality indicator, albeit underused among the physiological parameters that reflect plant quality. Recently, Liu et al [96,97] evaluated the effects of differences in temperature (DIF) between day and night on Astragalus membranaceus and Codonopsis lanceolata seedlings and found that a DIF of more than 10 • C was recommended for the production of highquality plants with the highest RDW/RL ratios for both species. Prior et al [129] have reported that a gradual increase in atmospheric CO 2 concentration and moderate water stress significantly improves the quality of the root system (both root density and dry weight) and the RDW/RL ratio in cotton plants.…”