The effects of heat shock duration and persistence on the induction of chilling tolerance in cucumber roots were studied using total root growth, electrolyte leakage, and membrane peroxidation as injury indices after chilling. Heat shock reduced the chilling induced electrolyte leakage, decreased membrane peroxidation as measured by MDA content, and resulted in a greater total root growth after chilling compared to the control. Heat shocks at 40°C, applied to 36 hr germinated seedlings for time periods from 1 to 15 hr, all resulted in an increase in chilling tolerance in a time-dependent manner. The heat shock induction of chilling tolerance is most effective when heat shock was imposed immediately before chilling, but the effect is persistent even 32 hr after heat shock when seedlings are held at 25°C before chilling. The possible mechanism of heat shock effect and its persistence will be discussed in relation to heat shock proteins and antioxidant enzyme systems.
Hua Zhang and Paul H. Jennings
Hua Zhang and Paul H. Jennings
Heat shock was applied to 32-h-old cucumber seedlings before chilling at 2.5C. Two cultivars, `Poinsett 76' and `Ashley', with different chilling tolerances, were tested. Using root growth after chilling as a measure of chilling tolerance, three heat shock regimes were found to induce chilling tolerance in both cultivars, with the most effective and uniform induction by heat shock at 40C for 3 h. `Ashley', the more chilling tolerant cultivar, exhibited a greater response to heat shock induction of chilling tolerance than `Poinsett 76'. Protein samples from roots were subjected to SDS-PAGE. Three low molecular weight heat shock proteins accumulated to a greater extent in the protein profile of heat-shocked `Ashley' roots. No such increase was found in the `Poinsett 76' roots. The induction of low molecular weight HSPs are discussed in relation to the heat-shock induction of chilling tolerance.
Zhiyi Bao, Bo Chen, and Hua Zhang
Loropetalum chinense var. rubrum accessions in China have not been adequately characterized for their morphological traits. Such characterization would be helpful in the development of improved cultivars and in cultivar classification. In this study, the morphological traits of 23 accessions were evaluated in spring, summer, and autumn to determine their phenotypic diversity. Cluster analysis with average distance was performed for the main traits of leaf and flower using data processing system software. The morphological investigation indicated that the number of flowering accessions and the flower number of L. chinense var. rubrum in spring were more than those in autumn. Only one accession (no. 13) yielded several flowers in summer. Some accessions had the same or similar color of leaf or flower in spring and autumn. Two accessions had the same flower color in spring and autumn, whereas others showed slightly different colors in spring and autumn. The 23 entries were grouped into four clusters in spring and five clusters in autumn based on multivariate analysis of nine classification variables. Each cluster had some specific characteristics of its own. Generally, the cluster formed first because of the similarity in leaf color. The accessions with similar flower color formed subclusters within a cluster. These accessions are an important resource for the establishment of a core collection of L. chinense var. rubrum in the world. Several accessions with good qualities were selected and should be further tested for horticultural merit.
Ying Wang, Tingting Xue, Xing Han, Lingxiao Guan, Liang Zhang, Hua Wang, and Hua Li
Kaolin particle film (KPF) is an aqueous formulation of chemically inert mineral particles that can be sprayed on the surface of crops to form a protective film, resulting in increased fruit yield and quality. In this work, the effects of kaolin-based, foliar reflectant particle film on grape composition and volatile compounds in ‘Meili’ (Vitis vinifera L.) grapes were investigated under different growth stages over two growing seasons. The 100-berry weight and titratable acid content were decreased, and the sugar and soluble solid contents were increased in grapes of plants treated with kaolin over 2 years. Compared with grapes from plants not sprayed with kaolin, the levels of total phenol, flavonoid, flavanol, tannin, and anthocyanins of grapes from plants treated with kaolin for 2 years were mostly increased. High-performance liquid chromatography (HPLC) analysis also revealed an increased content of monomeric anthocyanin and changed anthocyanin composition. However, there was little effect on the volatile compounds in the grapes. These results demonstrate that KPF can facilitate the accumulation of sugar and phenolics, thereby improving grape quality even in a humid climate.
Zhan Shu, Xue Zhang, Dianqiong Yu, Sijia Xue, and Hua Wang
Hybridization between species of the genus Juglans is common because of weak reproductive isolation mechanisms between closely related species with sympatric distributions. In this research, we investigated the possibility of naturally occurring interspecific hybrids between two species in the genus Juglans: persian walnut (Juglans regia) and chinese walnut (Juglans cathayensis). We used 12 pairs of microsatellite markers to analyze introgression between the two species. All amplified microsatellites were polymorphic in the two species. The result of Bayesian admixture analyses showed that introgression between the two species is rare; only three of nine individuals tentatively identified as hybrids, based on intermediate morphological characteristics, were defined as mixed genotypes. The other six putative hybrids and 156 morphologically pure individuals showed no sign of introgression.
Lu Zhang, You-biao Hu, Hua-sen Wang, Sheng-jun Feng, and Yu-ting Zhang
Plant growth and development are determined by complex exogenous and endogenous cues. A plant follows several temporally distinct developmental stages, including embryonic, vegetative, and reproductive. The vegetative stage, which is usually the longest stage, can be subdivided into juvenile and adult phases. The transition from the juvenile to the adult phase, also called the vegetative phase change, is characterized by anatomical, morphological, and physiological changes in the vegetative parts of the shoot. Recent studies in several systems have identified the genetic temporal mechanisms of this process, which is regulated by an endogenous age cue (i.e., microRNA156/157) and its targeted genes (i.e., Squamosa promoter binding protein-box transcription factors). This review summarizes the recent advances in the study of the underlying regulatory mechanisms of vegetative phase change. This review also describes the modes of miRNA action and the functions of their targeted genes in this highly conserved developmental process.
Xu-Wen Jiang, Cheng-Ran Zhang, Wei-Hua Wang, Guang-Hai Xu, and Hai-Yan Zhang
The effects of CaCl2, GA3, and H2O2 priming on Isatis indigotica Fort. seed germination characteristics, seedling growth parameters, and antioxidant enzyme activities under salt stress were investigated. NaCl had an adverse effect on the germination and seedling performance of I. indigotica. However, these three priming agents alleviated salt stress by increasing the germination percentage, improving seed vigor, accelerating germination velocity, and establishing strong seedlings. The optimal concentrations were 15 g/L for CaCl2, 0.2 g/L for GA3, and 40 mm for H2O2. Seed priming treatments enhanced the activities of antioxidant enzymes in seedlings, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), under a salt environment, which reduced the oxidative injury caused by salt. Seed priming is a promising technique that can enhance the ability of I. indigotica seed germination when salt is present.
Yan Yao, Yao Kong, Ping Zhang, Hua Zhang, Hong-di Huang, and Guang-guang Li
The rapid expansion of Asian populations in the United States presents significant requirements for Asian vegetables. Flowering chinese cabbage (Brassica rapa L. ssp. chinensis var. utilis Tsen et Lee) is one of the most popular vegetables in China. The main factors restricting the progress in its breeding and genetic studies is the time required in generating desired pure line populations. Doubled haploid (DH) populations of flowering chinese cabbage have not been established because of technical difficulties. An appropriate combined protocol for a fast generation cycling system could advance up to seven generations, allowing the production of pure line seeds within 336–420 days among four cultivars and one hybrid of flowering chinese cabbage. The previous six generation cycles were accelerated using the embryo culture plus soil method which bypassed seed maturation through in vitro culture of immature embryos and promoted plant reproduction under stressed conditions, then the seventh generation cycle was accomplished until mature seeds were harvested using the soil method. During the culture of immature embryos, 12-day-old embryos could germinate and develop successfully on a Murashige and Skoog medium (MS) medium () containing 10% young coconut juice. This combined protocol bypasses the current obstacles in constructing DH populations of flowering chinese cabbage and is a possible alternative for producing pure lines. Its wider adoption could facilitate the breeding and biological studies of other Brassicaceae vegetables.
Zhi-Rong Li, Kang-Di Hu, Fen-Qin Zhang, Shi-Ping Li, Lan-Ying Hu, Yan-Hong Li, Song-Hua Wang, and Hua Zhang
Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. However, the floral heads of broccoli experience rapid postharvest senescence. Here we found that hydrogen sulfide (H2S) treatment alleviated dark-promoted senescence in broccoli florets. H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. Gene expression analysis showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLH1, BoPPH, and BoRCCR. Expression of lipoxygenase gene BoLOX1 and the genes involved in the ethylene synthesis pathway, BoACS2 and BoACS3, were also down-regulated by H2S. The reduced expression level in cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 suggested the role of H2S in alleviating protein degradation during broccoli senescence. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes.
Hua Q. Zhao, Qing H. He, Li L. Song, Mei F. Hou, and Zhi G. Zhang
The procedure for Heuchera villosa ‘Caramel’ propagation was investigated, which involves shoot regeneration, rooting of regenerated shoots, and acclimation of regenerated plantlets. Petioles, as explants, were cultured on MS medium supplemented with 1-naphthylacetic acid (NAA), benzylaminopurine (BA), thidiazuron (TDZ) and callus formed on all media. Shoots were observed to proliferate from callus on media with BA and NAA, whereas no shoots regenerated on media with TDZ and NAA. On media containing 0.5 or 1.0 mg·L−1 BA in combination with NAA, the regenerated shoots showed severe hyperhydricity, whereas on media containing 0.1 mg·L−1 BA in combination with NAA, the regenerated shoots grew normally. The highest shoot induction rate, 90.6%, was obtained on media containing 0.1 mg·L−1 BA and 0.01 mg·L−1 NAA. The effects of indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and NAA on rooting of H. villosa ‘Caramel’ was explored. The highest rooting rate (95%) was obtained on 1/2 MS medium containing 0.2 mg·L−1 NAA. In the subsequent acclimation experiments, about 85% of rooted plantlets survived and grew normally.