Kalmia latifolia L. (mountain laurel), a member of Ericaceae, is a beautiful ornamental shrub native to the eastern United States. The plant is not common in the southeastern United States landscapes because of the limited heat tolerance of most commercial cultivars. Breeding of heat-tolerant cultivars can be achieved by cross hybridization, but is often challenged by low germination percentage, long germination time, and potential abortion of cross-hybridized seeds. We used in vitro seed germination to enhance germination and shorten germination time and investigated the appropriate collecting time, optimal basal medium, and pH for this approach. Collecting time affected in vitro seed germination, with more mature hybrid seeds [collected 4–5 months after pollination (MAP)] having higher germination rate (90% in 4 weeks) than the less mature seeds collected in 2 MAP (20% in 7 weeks). Seedlings from the mature seeds also produced two true leaves on average after 8 weeks of culture, whereas seedlings from the less mature seeds had no true leaves. Woody Plant Medium (WPM) better enhanced in vitro seed germination compared with Murashige and Skoog (MS) or Gamborg’s B5 (B5) medium. WPM yielded higher germination (98%) than MS (90%) and significantly greater total leaf area per seedling (67 mm3) than MS (50 mm3) and B5 (52 mm3) for seeds of ‘Firecracker’ × ‘Snowdrift’. Similar effects had been observed on seeds from ‘Little Linda’ × ‘Starburst’ and ‘Pristine’ × ‘Peppermint’. The pH ranging from 4.2 to 5.4 did not affect seed germination and seedling development of mountain laurel hybrids. Our protocol enabled early collection of mountain laurel hybrid seeds 1 month before their full maturation and permitted seeds to germinate in 4 weeks on WPM, which shortened the period from crossing to the seedling stage from up to 15 to 6 months and enhanced germination percentage from 30% to more than 90% compared with traditional seed germination. This protocol should be applied to promote the breeding and selection of new mountain laurel cultivars for the southeastern United States landscapes.
A nondestructive method for the determination of chlorophyll index for the tea plant based on reflectance spectral characteristics was investigated. Spectral data were collected from 184 samples with a spectroradiometer in a field experiment. Multivariate analysis techniques, including partial least squares (PLS) and multiple linear regression (MLR), were used for developing calibration models for the determination of chlorophyll index of the tea plant. The best calibration model was achieved using the PLS technique with a correlation coefficient (r) of 0.95, a se of prediction of 3.40, and a bias of 1.9e−06. When the model was used for predicting the unknown samples, good performance was also obtained with r of 0.91, se of calibration of 4.77, and bias of 0.02. Sensitive wavelengths were selected through loading analysis of latent variables in the optimal PLS model, and the validity of these wavelengths was proved by MLR and statistical analysis. Three fingerprint wavelengths (488, 695, and 931 nm) were determined and could potentially be used for developing a simple, low-cost, and efficient instrument for the measurement of chlorophyll index. The results proved the feasibility of reflectance spectra for measurement of chlorophyll index of the tea plant.
Mountain laurel (Kalmia latifolia) is an outstanding ornamental shrub due to its attractive foliage and showy inflorescences. Breeding efforts have led to improved selections that have predominantly been developed and evaluated in the northeastern United States. Consequently, most cultivars have largely been dismissed as incompatible for the southeastern U.S. environmental conditions by nursery growers and consumers. This study was conducted over a 4-year period to evaluate 21 popular mountain laurel cultivars, primarily developed in the northeastern United States, for container and field performance in Georgia. All cultivars yielded considerable growth in the first year of container trials, indicating production of mountain laurel as a 1-year container crop is feasible. Cultivars displayed significantly different total growth index throughout the container trial. Fast-growing cultivars such as Bullseye and Ostbo Red yielded more than 100, 150, and 250 cm of growth index in 1, 2, and 4 years, respectively. Conversely, cultivars that grew slower, such as Firecracker and Tinkerbell, had less than 80, 115, and 180 cm in 1, 2, and 4 years, respectively. Cultivars were classified into five groups, using principal component analysis, that included dwarf habit with pink flower, dwarf habit with nonpink flower, nondwarf habit with green stem and white flower, nondwarf habit with pigment-patterned flower, and nondwarf habit with pink flower. In a field study, performance rating of 21 cultivars ranged from 2.0 to 4.8 (out of 5.0) in 2014 and from 2.0 to 5.0 in 2015. Ten cultivars that received the highest ratings over these 2 years were selected for a subsequent field trial in 2016. Cultivars showed overall decreased ratings (1.0–3.3) from the previous 2 years because of late spring planting. ‘Ostbo Red’, ‘Pristine’, and ‘Tinkerbell’ had higher performance ratings, more net growth, and less decrease in maximum quantum yield, which indicated suitable adaptation to southeastern U.S. environmental conditions. Nursery growers and consumers should benefit from regional cultivar trial information derived from this study. ‘Ostbo Red’, ‘Pristine’, and ‘Tinkerbell’ performed well across trials and therefore are recommended for southeastern U.S. landscapes based on superior container and field performance, leaf spot (caused by Mycosphaerella colorata) tolerance, and morphologic distinctions.
Soluble acid invertase [SAI (Enzyme Commission 220.127.116.11)] plays an important role in catalyzing the hydrolysis of sucrose into hexoses and regulates floral development. Full-length cDNAs encoding RhSAI1 and RhSAI2 isoforms were cloned from Rhododendron hybrid ‘Yuqilin’ and they exhibited high amino acid sequence identity (89%) to each other. The protein sequences contain highly conserved motifs present in all SAIs, including the β-fructosidase motif N-D-P-(D/N), a putative active site W-E-C-(I/V)-D, and R-D-P. The expression of RhSAI1 and RhSAI2 genes was under spatial and temporal control. Expression of both RhSAI1 and RhSAI2 genes was most abundant in stems, and expression was lowest in roots and leaves, respectively. The expression of RhSAI2 was significantly lower than that of RhSAI1 in all organs. During floral development, RhSAI1 was highly expressed at the earliest stage (Stage I), decreased until Stage III, and increased again at the terminal stage. The pattern of RhSAI2 expression was distinctly different, showing a continuous increase during floral development. Consistent with the levels of RhSAI1 expression, SAI activity decreased during floral development and was inversely correlated with the soluble sugar content. Abundant expression of RhSAI1 at the transcriptional level in addition to high SAI activity during the initial stages of floral development may play a vital role in supplying the energy needed for rapid cell division and growth of flowers.
Sea buckthorn (Hippophae rhamnoides) is an ecologically and economically valuable species that has been widely cultivated as a new berry crop rich in nutritional and medicinal compounds. RNA Sequencing (RNA-Seq) simple sequence repeat (SSR) markers were developed to evaluate the genetic relationships among 91 plants of 31 cultivars from two subspecies, mongolica and sinensis, as well as intraspecific hybrids between them. A total of 7540 RNA-Seq SSRs were identified as potential molecular markers, in which AG/CT (27.57%) was the most abundant unit type. AT/AT (9.93%), and AAG/CTT (11.95%) are the other main repeat motifs. A total of 110 primer pairs were randomly selected for validation of amplification. Seventeen SSR loci, located in genes encoding metabolic processes and cellulose synthases, were identified to be polymorphic among different sea buckthorn cultivars. These SSR loci generated 48 alleles, ranging from 2 to 5 per locus. Cluster analysis based on the proportion of shared alleles and unweighted pair group method with arithmetic average (UPGMA) algorithm divided all the genotypes into two main groups, with all of the ssp. sinensis cultivars (native to China) and hybrids in one group and ssp. mongolica cultivars (introduced from Russia) in the other group, which was in good agreement with their taxonomic classification. The RNA-Seq SSRs developed in this study have a potential use in the conservation of sea buckthorn germplasm and marker-assisted breeding (MAB).
Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT50) using electrolyte leakage test (ELLT50) and triphenyltetrazolium chloride test (TTCLT50) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT50 was lower than the xylem TTCLT50, and the two sds were similar. The ELLT50 showed no significant correlation with any TTCLT50. For most species, the ELLT50 was higher than the cambium and phloem TTCLT50 and was not significant different with the xylem TTCLT50. The ELLT50 showed higher sd than any tissue TTCLT50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT50.
We quantitatively assessed the effects of a six-session edible horticultural therapy (EHT) program on long-term-hospitalized (LTH) female patients with schizophrenia. A total of 60 patients were enrolled in the project and randomly divided into an experimental group (30 patients, received EHT) and a control group (30 patients, did not receive EHT). The two groups were evaluated before and after EHT using the Brief Psychiatric Rating Scale (BPRS), the Chinese version Scale of Social Functioning for Psychotic Inpatients (SSFPI), and the Life Satisfaction Index A (LSIA). The clinical symptoms of patients with schizophrenia improved significantly and they recovered social function, but there was no significant change in life satisfaction. In the control group, clinical symptoms recovered but there was no improvement in social function and life satisfaction significantly decreased. In addition, patients in the EHT group expressed satisfaction with the program. In conclusion, EHT can improve the clinical symptoms of schizophrenia and promote recovery of social function; however, its impact on life satisfaction remains unclear.
Leaf stomata are the main channels for water loss of plants including cut flowers. In this study, we investigated the organographic distribution, morphological characteristics, light–dark response, and water loss contribution of stomata in cut carnations (Dianthus caryophyllus L. ‘Master’), which are prone to typical water deficits despite a few and small leaves. Stomata were observed in the upper and lower leaf epidermis, stem surface, abaxial bract epidermis, and abaxial sepal epidermis. Stomatal density (SD) on the stem surface was the highest and significantly greater than that on the upper and lower leaf and abaxial bract epidermis. The sepal epidermis had the lowest SD and the smallest stomata whereas the upper leaf epidermis had the largest stomata. Changes in the water loss rate increased in the light and decreased in the dark in both intact and leaves-removed cut carnations. The water loss rate of the former was greater than that of the latter. However, the water loss rate for the stem-only cut carnations had weak change rhythms and was much lower than that for the intact and leaves-removed cut carnations. These findings demonstrate the differential contributions of stomata in leaves, stems, and floral organs to water loss, and help to elucidate further the mechanism underlying postharvest water deficit in cut carnations.
To examine whether 1 mm of spermidine (Spd) modifies plant ethylene production in response to short-term salt stress, cucumber (Cucumis sativus) seedlings were grown in nutrient solution with or without 75 mm NaCl stress for 3 days, and the leaves were sprayed with 1 mm Spd or water (control). We investigate the effects of the treatments on ethylene production, 1-aminocyclopropane-1-carboxylate (ACC) content, 1-(malonylamino) cycolpvopane-1-carboxylic acid (MACC) content, activities of 1-aminocyclopropane-1-carboxylate synthase (ACS), and 1-aminocyclopropane-1-carboxylate oxidase (ACO) and gene expression of acs2, aco1, and aco2 in the cucumber leaves. The results indicate that ethylene production was increased significantly under salt stress as did ACC and MACC content, the activities of ACS and ACO, and the transcriptional level of acs2, whereas the gene expression of aco1 and aco2 was somewhat decreased. However, exogenous Spd treatment depressed the content of ACC and MACC, ACS activity, and the level of acs2 transcripts in the leaves of salt-stressed cucumber. Although the activity of ACO and gene expressions of aco1 and aco2 increased by Spd, ethylene emission was inhibited. Our results suggest that application of exogenous Spd could reverse salinity-induced ethylene production by inhibiting the transcription and activity of ACS under salt stress. We conclude that exogenous Spd could modify the biosynthesis of ethylene to enhance the tolerance of cucumber seedlings to salt stress.