Saxifraga Tourn. ex L. is rich in species diversity with about 440-500 species and broad distribution. The taxonomical issues of this genus have been continuously concerned by the botanists. Saxifraga has important ornamental and medicinal values. Some of European countries have made great efforts on the exploitation and utilization of its ornamental resources. China is one of the diversity centers of Saxifraga, but it has been lagged far behind Europe, USA and even Japan in exploitation and utilization on ornamental value of this genus. The world breeding work in Saxifraga started 150 years ago. By the end of 2022, the 1 692 names of cultivars had been on-line listed by The Saxifrage Society, but only one came from China. In this paper, the germplasm resources of Saxifraga, and progress on its classification and breeding are reviewed, and also the utilization of its ornamental resources is briefly introduced, which will provide an important reference for taxonomical research, breeding and application of this genus in China. The results are as follows: (1) Saxifraga is rich in germplasms, but many scientific issues remain in the evolutionary relationships of its subordinate systems, which require a systematic and in-depth investigation by integrating morphological and molecular biology methods. (2) The cultivars of this genus are mainly raised through cross-breeding and mutant selection, and the majority of cultivars are from the UK, Czech Republic, Germany, and the Netherlands. (3) The breeding of Saxifraga started very late in China, with only few cultivars from one breeding method.

Plants NADP-malic enzymes (NADP-MEs) act as a class of oxidative decarboxylase to mediate malic acid metabolism in organisms. Despite NADP-MEs have been demonstrated to play pivotal roles in regulating diverse biological processes, the role of NADP-MEs involving in plant growth and development remains rarely known. Here, we characterized the function of rice cytosolic OsNADP-ME2 in regulating plant height. The results showed that RNAi silencing and knock-out of OsNADP-ME2 in rice results in a dwarf plant structure, associating with significant expression inhibition of genes involving in phytohormone Gibberellin (GA) biosynthesis and signaling transduction, but with up-regulation for the expression of GA signaling suppressor SLR1. The accumulation of major bioactive GA1, GA4 and GA7 are evidently altered in RNAi lines, and exogenous GA treatment compromises the dwarf phenotype of OsNADP-ME2 RNAi lines. RNAi silencing of OsNADP-ME2 also causes the reduction of NADP-ME activity associating with decreased production of pyruvate. Thus, our data revealed a novel function of plant NADP-MEs in modulation of rice plant height through regulating bioactive GAs accumulation and GA signaling, and provided a valuable gene resource for rice plant architecture improvement.

Saxifraga Tourn. ex L. is rich in species diversity with about 440-500 species and broad distribution. The taxonomical issues of this genus have been continuously concerned by the botanists. Saxifraga has important ornamental and medicinal values. Some of European countries have made great efforts on the exploitation and utilization of its ornamental resources. China is one of the diversity centers of Saxifraga, but it has been lagged far behind Europe, USA and even Japan in exploitation and utilization on ornamental value of this genus. The world breeding work in Saxifraga started 150 years ago. By the end of 2022, the 1 692 names of cultivars had been on-line listed by The Saxifrage Society, but only one came from China. In this paper, the germplasm resources of Saxifraga, and progress on its classification and breeding are reviewed, and also the utilization of its ornamental resources is briefly introduced, which will provide an important reference for taxonomical research, breeding and application of this genus in China. The results are as follows: (1) Saxifraga is rich in germplasms, but many scientific issues remain in the evolutionary relationships of its subordinate systems, which require a systematic and in-depth investigation by integrating morphological and molecular biology methods. (2) The cultivars of this genus are mainly raised through cross-breeding and mutant selection, and the majority of cultivars are from the UK, Czech Republic, Germany, and the Netherlands. (3) The breeding of Saxifraga started very late in China, with only few cultivars from one breeding method.

This research mainly focused on the leaf color change and photosystem function differentiation between Loropetalum chinense and its variety L. chinense var. rubrum under heat stress, which were tightly concerned about their ornamental traits and growth. L. chinense 'Xiangnong Xiangyun' (X) and L. chinense var. rubrum 'Xiangnong Fendai' (F) and L. chinense var. rubrum 'Hei Zhenzhu' (H) were chosen to be experimented on to investigate whether leaf color morphology and pigment composition could influence the adaptability of plants to high temperature in order to select foliage plants which posses stable leaf color and better adaptability for hot regions. The plants were cultured in hot environment (40 °C/33 °C, day/night) and normal environment (25 °C/18 °C, day/night). Phenotype and anatomic observation of three cultivars were made and leaf color indices and pigment contents were measured. During the experiment, H and F gradually turned green, total anthocyanins contents significantly decreased in them, however, chlorophyll b contents increased in all three cultivars. In addition, the initial fluorescence (Fo) decreased in X, while increased in H and F. For the maximum fluorescence (Fm) and maximum photochemical efficiency of PSII (Fv/Fm), they only increased in H and decreased in both F and X. The non-photochemical chlorophyll fluorescence quenching (NPQ) also increased in H and decreased in F. For X, it increased at first then gradually decreased. The coefficient of photochemical quenching all increased at first then gradually decreased. Correlation analysis between showed that there was relatively strong connection between anthocyanins, flavonoids and chlorophyll fluorescence parameters, especially NPQ, proved anthocyanins and flavonoids might not only involved in enriching leaf color, but also interfered with the protection of photosystem. Generally speaking, we found higher anthocyanin and flavonoids content level not only dramatically enriched the leaf color of L. chinense var. rubrum cultivars, but also offered more potential antioxidant to keep their normal growth when encountered heat stress.

BACKGROUND:Loropetalum chinense var. rubrum (L. chinense var. rubrum) is a precious, coloured-leaf native ornamental plant in the Hunan Province. We found an L. chinense var. rubrum tree with three different leaf colours: GL (green leaf), ML (mosaic leaf), and PL (purple leaf). The mechanism of leaf coloration in this plant is still unclear. Therefore, this study aimed to identify the metabolites and genes involved in determining the colour composition of L. chinense var. rubrum leaves, using phenotypic/anatomic observations, pigment content detection, and comparative metabolomics and transcriptomics.RESULTS:We observed that the mesophyll cells in PL were purple, while those in GL were green and those in ML were a mix of purple-green. The contents of chlorophyll a, b, carotenoids, and total chlorophyll in PL and ML were significantly lower than those in GL. While the anthocyanin content in PL and ML was significantly higher than that in GL. The metabolomics results showed the differences in the content of cyanidin 3-O-glucoside, delphinidin 3-O-glucoside, cyanidin 3,5-O-diglucoside, pelargonidin, and petunidin 3,5-diglucoside in ML, GL, and PL were significant. Considering that the change trend of anthocyanin content change was consistent with the leaf colour difference, we speculated that these compounds might influence the colour of L. chinense var. rubrum leaves. Using transcriptomics, we finally identified nine differentially expressed structural genes (one ANR (ANR1217); four CYP75As (CYP75A1815, CYP75A2846, CYP75A2909, and CYP75A1716); four UFGTs (UFGT1876, UFGT1649, UFGT1839, and UFGT3273) and nine transcription factors (two MYBs (MYB1057 and MYB1211), one MADS-box (MADS1235), two AP2-likes (AP2-like1779 and AP2-like2234), one bZIP (bZIP3720), two WD40s (WD2173 and WD1867) and one bHLH (bHLH1631) that might be related to flavonoid biosynthesis and then impacted the appearance of colour in L. chinense var. rubrum leaves.CONCLUSION:This study revealed potential molecular mechanisms associated with leaf coloration in L. chinense var. rubrum by analyzing differential metabolites and genes related to the anthocyanin biosynthesis pathway. It also provided a reference for research on leaf colour variation in other ornamental plants.

As a shade plant with high ornamental value, Saxifraga stolonifera is often used in landscape of courtyards and gardens. The light intensity may have an important infuence on its growth performance, especially on leaf color, formation and coloration of leaf variegation, which subsequently affects its ornamental value. However, the related study has not been reported before. In order to explore the adaptability of different cultivars of S. stolonifera to light intensity and understand their light or shade tolerance, three internationally-registered cultivars raised in China were used as the experimental materials, the effects of five light intensity treatments (100%, 85%, 60%, 40% and 15%) on plant growth and development and photosynthetic physiological indexes were investigated. The suitable indexes of light intensity for S. stolonifera were screened by the principal component analysis, and the light tolerance of the cultivars was evaluated by membership function analysis. The results were as follows: (1) The number of blades, leaf length, leaf width, leaf area, specific leaf area, chlorophyll a, chlorophyll b and total chlorophyll contents increased with shading. (2) The number of stolons, fresh weight above ground, dry weight above ground, stolon diameter, and the contents of carotenoid and flavonoids increased first and then decreased. (3) The maximum fluorescence value and the contents of soluble sugar, soluble protein and malondialdehyde of the leaves decreased with shading. (4) By analysis of principal component and membership function, the significant differences were found in the adaptability of the three cultivars to light intensity, ‘Xue Wen’ > ‘Tianmu Enci’ > ‘Hei Kui’. In which, 40% light intensity was optimal for ‘Xue Wen’, and 15%-40% light intensities were optimal for ‘Tianmu Enci’ and ‘Hei Kui’. Therefore, in horticultural practice, the suitable light intensity should be considered according to the cultivars of Saxifraga.

Abstract Background: Loropetalum chinense var. rubrum is a typical colorful ornamental and medicinal plant. However, the coloration information and potential colorful molecular mechanisms of its leaves remain unclear. We analyzed structural and regulatory genes for flavonoid metabolites and anthocyanin biosynthesis in 3 kinds color of leaves（PL, pink leaves; ML, middle color leaves; GL, green leaves) of L. chinense var. rubrum.Results: Metabolic detection to the samples showed that there were significant differences in the metabolites accumulated in different color leaves. Meanwhile, transcriptome indicated that DFR, ANR and UFGT genes in L. chinense var. rubrum might be one of the reasons for the accumulation of anthocyanin in ML and GL. We also found that several key members of the MYB, BHLH, and WD40 gene families played important roles in regulating the accumulation of flavonoids in plants, which were considered to be the main drivers of transcriptional changes in different colors of L. chinense var. rubrum leaves. Our findings provided a comprehensive data set for the metabolism and transcription of L. chinense var. rubrum as well as candidate structures and transcription factors information related to leaf pigmentation.Conclusions: The conclusion would provide useful information for elucidating the formation of leaf color and anthocyanin accumulation in L. chinense var. rubrum，which could also explain the color variation in its leaves.

IntroductionLoropetalum chinense var. rubrum blooms 2-3 times a year, among which the autumn flowering period has great potential for exploitation, but the number of flowers in the autumn flowering period is much smaller than that in the spring flowering period.MethodsUsing ‘Hei Zhenzhu’ and ‘Xiangnong Xiangyun’ as experimental materials, the winter growth environment of L. chinense var. rubrum in Changsha, Hunan Province was simulated by setting a low temperature of 6-10°C in an artificial climate chamber to investigate the effect of winter low temperature on the flowering traits and related gene expression of L. chinense var. rubrum.ResultsThe results showed that after 45 days of low temperature culture and a subsequent period of 25°C greenhouse culture, flower buds and flowers started to appear on days 24 and 33 of 25°C greenhouse culture for ‘Hei Zhenzhu’, and flower buds and flowers started to appear on days 21 and 33 of 25°C greenhouse culture for ‘Xiangnong Xiangyun’. The absolute growth rate of buds showed a ‘Up-Down’ pattern during the 7-28 days of low temperature culture; the chlorophyll fluorescence decay rate (Rfd) of both materials showed a ‘Down-Up-Down’ pattern during this period. The non-photochemical quenching coefficient (NPQ) showed the same trend as Rfd, and the photochemical quenching coefficient (QP) fluctuated above and below 0.05. The expression of AP1 and FT similar genes of L. chinense var. rubrum gradually increased after the beginning of low temperature culture, reaching the highest expression on day 14 and day 28, respectively, and the expression of both in the experimental group was higher than that in the control group. The expressions of FLC, SVP and TFL1 similar genes all decreased gradually with low temperature culture, among which the expressions of FLC similar genes and TFL1 similar genes in the experimental group were extremely significantly lower than those in the control group; in the experimental group, the expressions of GA3 similar genes were all extremely significantly higher than those in the control group, and the expressions all increased with the increase of low temperature culture time.DiscussionWe found that the high expression of gibberellin genes may play an important role in the process of low temperature promotion of L. chinense var. rubrum flowering, and in the future, it may be possible to regulate L. chinense var. rubrum flowering by simply spraying exogenous gibberellin instead of the promotion effect of low temperature.

以3个檵木属优良株系为材料,通过英国皇家园艺协会比色卡(RHSCC)比色、分光色差仪测色、叶片解剖观察、色素含量测定和超高效液相色谱质谱联用(UPLC-MS/MS)技术及迈维代谢自建植物特有数据库(MWDB)和代谢物信息公共平台探讨其叶色呈色的化学机制.结果表明:3个檵木属株系叶色存在显著差异,红花檵木叶片的栅栏组织、海绵组织、气孔的副卫细胞和下表皮细胞分布有花青素苷.红花檵木叶片中总花青素苷与叶绿素总含量的高比值是叶片呈现红色的直接原因.从供试材料中共鉴定出185种类黄酮化合物(包括花青素苷15种、黄酮苷104种、黄酮醇苷39种、黄烷酮苷20种、异黄酮苷7种)和22种除类黄酮以外的多酚类化合物(包括酚酸19种,原花青素3种).以天竺葵素、矢车菊素、飞燕草素、芍药花素、矮牵牛素和锦葵素为苷元的13种花青素苷是红花檵木呈色的主要色素成分;黄酮苷、黄酮醇苷、黄烷酮苷、异黄酮苷、酚酸、原花青素等非花青素苷类多酚,是影响檵木属植物叶片呈色的辅助色素成分;这些多酚化合物在叶片中含量的显著差异,造成了不同红花檵木品种的叶片呈现出不同的色泽.