Treatment with Calcium Chloride Enhances Water Deficit Stress Tolerance in Viola (Viola cornuta)

Water deficit stress can reduce the postproduction shelf life and marketability of floriculture crops. To alleviate the damage by water deficiency, plants need to limit transpirational water loss by inducing stomatal closure. Osmotic stress induces stomatal closure like the response to water deficit stress. It could be used as a convenient tool to enhance water deficit stress tolerance by reducing water loss. The objective of this research was to investigate whether osmotic treatment with a high concentration of chemical solutions could trigger a response to osmotic stress so that stomatal closure can be induced, resulting in enhanced water deficit stress tolerance in viola (Viola cornuta ‘Sorbet XP Yellow’). Osmotic treatments with CaCl2, Ca(NO3)2, NaCl, NaNO3, BaCl2, Ba(NO3)2, and mannitol were applied at the osmotic potentials (cS) of L1.3 and L2.0 MPa. Chemical treatments [except Ca(NO3)2, NaCl, and mannitol] helped to delay wilting and gave a longer shelf life, up to 5.2 days over that of the control, 2.5 days. However, leaf necrosis was observed on the violas treated with NaCl, NaNO3, BaCl2, Ba(NO3)2, and mannitol. CaCl2 was the most effective agent in delaying wilting under water deficit stress in viola without leaf necrosis. Compared with the control, violas treated with CaCl2 at 200 and 300 mM showed an increase in shelf life by 2.6 and 1.2 days, respectively. Stomatal conductance (gS) was reduced within 4 hours after treatment with CaCl2 compared with that of control violas. Leaf relative water content (RWC) of control violas was dramatically reduced 3 days after treatment and fell below 50% on day 4, while CaCl2-treated violas maintained higher leaf RWC (70% to 81%) during the water deficit period. These results indicated that osmotic treatment with the high concentration of CaCl2 caused stomatal closure, resulting in a reduction of water loss and an extension of shelf life under water deficit stress in viola

Metabolomic analyses provide insights into the preharvest rind disorder in Satsuma Owari Mandarin

Citrus fruit’s appearance is the primary criterion used to assess its quality for the fresh market, hence the rind’s condition is a crucial quality trait. Pre-harvest rind disorder is one of the major physiological problems in mandarins. The disorder occurs right before harvest following rain events in some Mandarin varieties. Despite the economic damage caused by this kind of disorder, very limited information is available about the molecular mechanisms underlying the occurrence of this disorder. In the present study, we evaluated the primary metabolites, antioxidants, and hormones associated with the pre-harvest rind disorder in Mandarins. The study was carried out using ten-year-old ‘Owari’ Satsuma mandarin trees grafted on ‘Carrizo’ rootstock and grown in a commercial orchard in San Joaquin Valley, California, USA. Samples were collected from healthy tissue of healthy fruit (HF_HT), healthy tissue of damaged fruit (DF_HT), and damaged tissue of damaged fruit (DF_DT). Damaged fruit (DF_HT and DF_DT) showed lower cellulose concentrations than healthy fruit tissues (HF_HT), however, had similar contents of pectin and hemicellulose. The antioxidant activities showed no significant difference in all paired comparisons between samples as expressed in the malondialdehyde (MDA) content. However, DF_DT had a higher H2O2 content compared to HF_HT, but DF_HT had a similar content to that of HF_HT. Furthermore, peroxidase (POD) and polyphenol oxidase (PPO) activities were increased in DF_DT compared to HF_HT (P = 0.0294) and DF_HT (P = 0.0044), respectively. Targeted metabolomics analysis revealed that a total of 76 metabolites were identified in Satsuma rind tissues, and the relative concentrations of 43 metabolites were significantly different across studied samples. The hormonal analysis showed the involvement of jasmonate O-methyltransferase, jasmonic acid-amido synthetase JAR1-like, and JA-isoleucine may key role in causing the rind disorder in mandarins. In addition, the damaged fruit tissues have a higher level of jasmonic acid (JA), 12-oxo-phytodienoic acid, and JA-isoleucine than undamaged tissue

Enhancing Water Stress Tolerance in Floriculture Crops

Water deficit is one of the major constraints on plant growth and development, causing reduction of crop productivity. To minimize water loss, among many adaptation strategies, plants close their stomata to reduce transpiration. The stomatal closure is regulated by light, internal CO2 concentration, and plant hormones, mainly abscisic acid. Plants’ response mechanisms to water deficit are complex processes involving numerous genes and various signaling pathways. Floriculture crops are often exposed to water deficit during shipping and retailing, and these periods often result in damaged crops and profit loss. Understanding of plant responses to water deficit stress will provide us an opportunity to develop floriculture crops with enhanced water deficit tolerance. The long-term goal of this research is to enhance water deficit stress tolerance in floriculture crops employing physiological and genetic technologies. As a practical approach, five antitranspirants, chemicals to reduce transpirational water loss, were evaluated for enhancing temporary water deficit tolerance in bedding plants. One physical [β-pinene polymer (βP)] and one physiological [a biological active form of abscisic acid (s-ABA)] antitranspirants enhanced tolerance to water deficit stress by blocking stomatal and inducing stomatal closure, respectively. However, βP caused floral damage and s-ABA caused chlorosis on the margin of leaves in some cultivars. To develop a more effective tool with minimal damage to plants, osmotic treatments was examined in viola. The osmotic treatment with high concentration of CaCl2 induced stomatal closure, resulting in delayed plant wilting through reduction of transpirational water loss and maintenance of high water content in plant leaves. In addition, CaCl2 treatment did not show any visual damage on plants. The osmotic treatment will allow floriculture crops to temporary tolerate water deficit stress without significant loss of postproduction quality. To investigate mechanisms of water stress responses at the molecular level, time-course transcriptome analysis was performed in petunia leaves at the early stage of water deficit. A total 6670 genes were differentially expressed under water deficit stress conditions. Gene Ontology analysis revealed that redox homeostasis processes with sulfur metabolism were enriched under water deficit stress. Genes encoding components of plant hormones, abscisic acid and ethylene, biosynthesis and signal transduction pathways were differentially expressed at the early stage of water deficit. Thirty-four transcription factor families were identified in petunia, and one member of AP2/ERF family, PhERF039, were selected for functional analysis. Under-expression of PhERF039 reduced stomatal conductance in addition to phenotypes related to development: delayed flowering and development of a rosette morphology. Although the result of stomatal conductance seemed to indicate that PhERF039 might play as a negative regulator in stomatal closure under water deficit, further analysis is required using additional independent transgenic lines. Transcriptomic data may provide insights into understanding water stress-responsive networks as well as opportunities to engineer floricultural crops with the enhanced water deficit tolerance traits

Evaluation of Calcium Application Methods on Delaying Plant Wilting under Water Deficit in Bedding Plants

Floriculture crops can lose their aesthetic quality due to water deficit during postproduction. Calcium is a secondary messenger in plant stress signaling, and the treatment of calcium has been proposed to alleviate damage by various abiotic stresses. The objective of this research was to evaluate application methods of calcium to delay plant wilting under water deficiency in three species of bedding plants: viola (Viola cornuta), impatiens (Impatiens walleriana), and petunia (Petunia grandiflora). Three application methods were compared including spray, drench, and pre-drench. Calcium was applied as CaCl2 and Ca(NO3)2 at three concentrations ranging from 50 to 300 mM. The effect of calcium on shelf life was species-dependent, increasing shelf life in viola and impatiens, but not in petunia. Viola showed increased shelf life up to 154% and 400% in drench and pre-drench applications, respectively, compared to the control. In impatiens, spray and pre-drench applications delayed wilting symptoms by 53% and 200%, respectively. Comparing calcium sources, CaCl2 was the most effective as a drench, while Ca(NO3)2 pre-drench application effectively delayed wilting. There was no difference between CaCl2 and Ca(NO3)2 in spray application. These results provided the optimum application methods to delay plant witling and the potential of calcium application on enhancing water deficit tolerance in floriculture crops

DataSheet_1_Metabolomic analyses provide insights into the preharvest rind disorder in Satsuma Owari Mandarin.pdf

Citrus fruit’s appearance is the primary criterion used to assess its quality for the fresh market, hence the rind’s condition is a crucial quality trait. Pre-harvest rind disorder is one of the major physiological problems in mandarins. The disorder occurs right before harvest following rain events in some Mandarin varieties. Despite the economic damage caused by this kind of disorder, very limited information is available about the molecular mechanisms underlying the occurrence of this disorder. In the present study, we evaluated the primary metabolites, antioxidants, and hormones associated with the pre-harvest rind disorder in Mandarins. The study was carried out using ten-year-old ‘Owari’ Satsuma mandarin trees grafted on ‘Carrizo’ rootstock and grown in a commercial orchard in San Joaquin Valley, California, USA. Samples were collected from healthy tissue of healthy fruit (HF_HT), healthy tissue of damaged fruit (DF_HT), and damaged tissue of damaged fruit (DF_DT). Damaged fruit (DF_HT and DF_DT) showed lower cellulose concentrations than healthy fruit tissues (HF_HT), however, had similar contents of pectin and hemicellulose. The antioxidant activities showed no significant difference in all paired comparisons between samples as expressed in the malondialdehyde (MDA) content. However, DF_DT had a higher H2O2 content compared to HF_HT, but DF_HT had a similar content to that of HF_HT. Furthermore, peroxidase (POD) and polyphenol oxidase (PPO) activities were increased in DF_DT compared to HF_HT (P = 0.0294) and DF_HT (P = 0.0044), respectively. Targeted metabolomics analysis revealed that a total of 76 metabolites were identified in Satsuma rind tissues, and the relative concentrations of 43 metabolites were significantly different across studied samples. The hormonal analysis showed the involvement of jasmonate O-methyltransferase, jasmonic acid-amido synthetase JAR1-like, and JA-isoleucine may key role in causing the rind disorder in mandarins. In addition, the damaged fruit tissues have a higher level of jasmonic acid (JA), 12-oxo-phytodienoic acid, and JA-isoleucine than undamaged tissue.</p

Ambient particulate matter and surrounding greenness in relation to sleep quality among pregnant women: A nationwide cohort study

Background: Particulate air pollution and residential greenness are associated with sleep quality in the general population; however, their influence on maternal sleep quality during pregnancy has not been assessed. Objective: This cross-sectional study investigated the individual and interactive effects of exposure to particulate matter (PM) air pollution and residential greenness on sleep quality in pregnant women. Methods: Pregnant women (n = 4933) enrolled in the Korean Children's Environmental Health Study with sleep quality information and residential address were included. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). The average concentrations of PM (PM2.5 and PM10) during pregnancy were estimated through land use regression, and residential greenness in a 1000 m buffer area around participants' residences was estimated using the Normalized Difference Vegetation Index (NDVI1000-m). Modified Poisson regression models were used to estimate the associations between PM and NDVI and poor sleep quality (PSQI >5) after controlling for a range of covariates. A four-way mediation analysis was conducted to examine the mediating effects of PM. Results: After adjusting for confounders, each 10 μg/m3 increase in PM2.5 and PM10 exposure was associated with a higher risk of poor sleep quality (relative risk [RR]: 1.06; 95% confidence interval [CI]: 1.01, 1.11; and RR: 1.09; 95% CI: 1.06, 1.13, respectively), and each 0.1-unit increase in NDVI1000-m was associated with a lower risk of poor sleep quality (RR: 0.97; 95% CI: 0.95, 0.99). Mediation analysis showed that PM mediated approximately 37%–56% of the association between residential greenness and poor sleep quality. Conclusions: This study identified a positive association between residential greenness and sleep quality. Furthermore, these associations are mediated by a reduction in exposure to particulate air pollution and highlight the link between green areas, air pollution control, and human health