Jujuba Mill Research Articles

Effect of plant cover type on soil water budget and tree photosynthesis in jujube orchards

The traditional soil management practice used in rainfed orchards in the Chinese Loess Plateau is clear cultivation (bare soil). This system leads to severe water erosion and considerable loss of water as runoff during heavy rainfall, especially on steep slopes. Plant cover systems represent a controversial alternative to the clear cultivation system. Although cover plants strongly promote water infiltration during rainfall, they may also compete with the trees for limited soil water. In this study, water regimes and inhibition of jujube (Ziziphus jujube Mill.) tree photosynthesis by water stress were compared across two types of soil management strategy: 1) a traditional clear cultivation system (CC); and 2) three plant cover systems (PCS) using different species, namely birdsfoot trefoil (Lotus corniculatus L.), cocksfoot (Dactylis glomerata L.) and white clover (Trifolium repens L.), in constructed soil macrocosms (0.8×0.8×2.0m) under simulated rainfall regimes. The PCS resulted in the infiltration of significantly more water during a rainfall event of about 60mm (infiltration coefficients 86%–91% for PCS and 68% for CC). The superior infiltration achieved in the PCS treatments was then gradually offset by their extra water consumption compared with that of CC. During a light rainfall event (rainfall amount: 30mm), runoff became negligible (less than 1.5% of the total rainfall amount) and the plant cover systems had mainly negative effects, including faster development of drought and water-mediated photosynthesis inhibition in jujube leaves. The white clover cover treatment showed the lowest runoff (runoff coefficient: 15% for the heavy rainfall and 3% for the light rainfall), the most conservative water consumption and the weakest inhibitory effects on jujube photosynthesis (net assimilation rate: >8μmol CO2 m−2s−1) among the three plant cover treatments. The white clover cover treatment is thus recommended as the most suitable choice for jujube orchards in the Loess Plateau area.

Effects of pruning intensity on jujube transpiration and soil moisture of plantation in the Loess Plateau

In order to ease soil desiccation and prevent ecological deterioration in the Loess Plateau, where jujube (Zizyphus jujube MIll) is widely cultivated as a drought tolerant plant, four pruning intensities (PI), from PI-1 (light) to PI-4 (heavy) were set up based on total length of secondary branches to study the effects of pruning on transpiration and soil moisture in jujube plantations. Furthermore, growth indexes were regularly monitored to estimate jujubes biomass. Sap flow, meteorological and soil moisture conditions were monitored using thermal dissipation probes (TDP), weather station (RR-9100) and the combination of time domain transmission (TDT) technology and neutron moisture gauges (CNC503B), respectively. The results showed that daily actual transpiration of jujube was positively correlated with leaf biomass. Compared with PI-1, jujube transpiration during growth period under PI-2, PI-3, and PI-4 dropped by 11.1%, 29.2%, and 47.9%, respectively. On the contrary, annual water storage under PI-2, PI-3, and PI-4 increased by 6.29 mm, 25.78 mm and 34.74 mm while water use efficiency increased by 5.1%, 15.7% and 24.2%, respectively. Overall, increase in pruning intensity could significantly reduce water consumption of jujube and improve soil moisture in jujube plantations.

Effects of Edible Coatings on Quality and Antioxidant Activity of Zizyphus Jujuba Miller cv. Dongzao During Storage

The development of edible coatings has been lauded with respect to their safety and effectiveness. In this study, we researched the effects of edible coatings (2% CaCl2, 1% chitosan and 1% pullulan) on the nutrient content and antioxidant abilities of jujube (Zizyphus jujuba Miller cv. Dongzao). Using the new analysis technique for order of preference by similarity to ideal solution (TOPSIS), we evaluated the effects of these coatings. Compared with the control fruit group, test results showed that coating treatment significantly delayed fruit senescence. Specifically, CaCl2 treatment not only maintained fruit storage quality and antioxidant activity but also restrained the production and accumulation of malondialdehyde in jujube. Chitosan treatment delayed decreases in secondary metabolites and superoxide dismutase and catalase activity. Pullulan coatings performed better in terms of proanthocyanidin and cyclic adenosine monophosphate (cAMP). We also used TOPSIS to evaluate the preservation effect of different film coatings and found 2% CaCl2 to be the best treatment for jujube, followed by 1% chitosan and 1% pullulan. Based on the appropriate materials and concentration of the film coatings, edible coatings have the potential to retain the quality and antioxidant capacity of the Chinese jujube cv. Dongzao.

Fate of triadimefon and its metabolite triadimenol in jujube samples during jujube wine and vinegar processing

Chinese jujube (Zizyphus jujuba Miller) is an indigenous fruit with Chinese characteristics in China which is widely used in traditional medicines and also consumed as a food material. Chinese jujube is subjected to wide varieties of pesticides like triadimefon which are harmful to humans. In present study, the fate of triadimefon and its metabolite triadimenol during jujube wine and vinegar fermentation processing was assessed. Jujube samples collected from plants sprayed with triadimefon from field trials. The analysis of triadimefon and triadimenol residues were carried out by gas chromatography–mass spectrometry (GC-MS) at different steps of the fermentation i.e fresh jujube, first and second jujube juice and pomace, jujube wine, and jujube vinegar. Processing factors (Pfs), which is defined as the ratio of pesticide residues in jujube sample to that in jujube wine or vinegar samples, were lower than 1 for triadimefon, indicating that food processing could reduce the pesticide level. But triadimefon was metabolised to triadimenol during this process with the Pfs of triadimenol in jujube wine and vinegar were 1.38 and 1.13, respectively, indicating that more attention is needed towards the metabolites during the processing. The study indicates the level of safety towards triadimefon in jujube beverage processing and allows the refining of the dietary risk analysis.

In Vivo Fast Induction of Homogeneous Autopolyploids via Callus in Sour Jujube (Ziziphus acidojujuba Cheng et Liu)

Polyploidization has been demonstrated as a very effective approach in fruit tree improvement. Sour jujube (Ziziphus acidojujuba Cheng et Liu) is a promising diploid wild, traditional fruit species (2n = 2x = 24) that is rich in vitamin C, which is the main rootstock of Chinese jujube (Z. jujuba Mill.). The novel method we developed for rapid in vivo induction of homogeneous autopolyploids (IVIHA) via callus in Chinese jujube was first applied and further optimized in sour jujube. Under optimized conditions, an average of one pure autotetraploid shoot could be regenerated from one treated branch, thereby indicating a relatively high efficiency rate. A total of 9 pure autotetraploid genotypes were created, and one of these was released as a new cultivar named ‘Zhuguang’ in 2015. Moreover, unexpected octoploids and hexaploids were also simultaneously created and detected. The leaves of tetraploids were thicker, broader, and darker in color than those of the original diploids, whereas the leaf sizes of octoploids were much smaller compared to that of diploids. However, stoma size increased with the occurrence of ploidy, mainly from diploid to octoploid. The well grown ploidies of jujube included diploids, triploids, and tetraploids. Anatomical observation indicated that adventitious buds/shoots emerged from the callus that formed on the cut, which was then followed by the development of connective vascular tissues between the adventitious bud and the stock plant tissue. This study demonstrates the universality of the IVIHA method that was initially developed in Chinese jujube, as well as provides a foundation for high-efficiency pure polyploid induction in sour jujube.

Simultaneous determination of rhamnose, xylitol, arabitol, fructose, glucose, inositol, sucrose, maltose in jujube (Zizyphus jujube Mill.) extract: comparison of HPLC-ELSD, LC-ESI-MS/MS and GC-MS.

BackgroundJujube extract is commonly used as a food additive and flavoring. The sensory properties of the extract, especially sweetness, are a critical factor determining the product quality and therefore affecting consumer acceptability. Small molecular carbohydrates make major contribution to the sweetness of the jujube extract, and their types and contents in the extract have direct influence on quality of the product. So, an appropriate qualitative and quantitative method for determination of the carbohydrates is vitally important for quality control of the product.ResultsHigh performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD), liquid chromatography-electronic spay ionization tandem mass spectrometry (LC-ESI-MS/MS), and gas chromatography–mass spectrometry (GC–MS) methods have been developed and applied to determining small molecular carbohydrates in jujube extract, respectively. Eight sugars and alditols were identified from the extract, including rhamnose, xylitol, arabitol, fructose, glucose, inositol, sucrose, and maltose. Comparisons were carried out to investigate the performance of the methods. Although the methods have been found to perform satisfactorily, only three sugars (fructose, glucose and inositol) could be detected by all these methods. Meanwhile, a similar quantitative result for the three sugars can be obtained by the methods.ConclusionsEight sugars and alditols in the jujube extract were determined by HPLC-ELSD, LC-ESI-MS/MS and GC–MS, respectively. The LC-ELSD method and the LC-ESI-MS/MS method with good precision and accuracy were suitable for quantitative analysis of carbohydrates in jujube extract; although the performance of the GC–MS method for quantitative analysis was inferior to the other methods, it has a wider scope in qualitative analysis. A multi-analysis technique should be adopted in order to obtain complete constituents of about the carbohydrates in jujube extract, and the methods should be employed according to the purpose of analysis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-016-0171-2) contains supplementary material, which is available to authorized users.

Phenolic composition, ascorbic acid content, and antioxidant capacity of Spanish jujube (Ziziphus jujube Mill.) fruits

The interest in Ziziphus jujube is growing because it is an excellent source of nutrients and phytochemicals, and can contribute to a healthy diet. Nutritional compounds (phenolic compounds and l-ascorbic acid), and antioxidant capacity of 4 Spanish jujube cultivars were studied. Polyphenols were identified by LC–MS–QTof and quantified by UPLC–PDA–FL. A total of 25 polyphenolic compounds were identified and classified as 10 flavan-3-ols, 13 flavonols, 1 flavanone, and 1 dihydrochalcone. The content of total polyphenols (TP) ranged from 1442 to 3432mg/100g dry matter (dm) in fruits of the cultivars ‘DAT’ and ‘PSI’, respectively. Flavan-3-ols, the major group of polyphenols in jujube represented ∼92% of the TP content, whereas flavonols only amounted for about ∼8% each. The content of l-ascorbic acid was very high and took values in the range of 387–555mg/100g fresh weight (fw). Some Spanish jujube cultivars, especially ‘PSI’ and ‘MSI’, may be selected to promote the growth of cultivars with valuable nutritional and phytochemical beneficial effects on human health.

Changes in phenolic compounds and their antioxidant capacities in jujube (Ziziphus jujuba Miller) during three edible maturity stages

This study investigated the changes in total phenolic content (TPC), total flavonoid content (TFC), individual phenolic compound content, DPPH radical scavenging activity and antioxidant capacity measured by FRAP assay of four phenolic fractions (free, esterified, glycosided and insoluble-bound) from jujube during three edible maturity stages. The maturity stages of jujubes were established as white maturity (WM), half-red maturity (HM) and red maturity (RM). The free fraction in jujube at WM stage had the highest TPC, TFC, total phenolic acid contents, and antioxidant capacities. The phenolic contents and their activities greatly decreased with the increasing maturity stage. Caffeic acid was the most predominant in all detected phenolic compounds at WM stage, while rutin dominated at HM and RM stages. Even though most of phenolic compounds with antioxidant activity in jujube existed at the WM stage as the free form, the insoluble-bound fractions also contained a large number of phenolic compounds.

Drying kinetics and quality attributes of jujube (Zizyphus jujuba Miller) slices dried by hot-air and short- and medium-wave infrared radiation

As representatives of the traditional and innovative drying method, hot-air (HA) and short- and medium-wave infrared radiation (SMIR) drying were chosen to conduct comparative study, respectively. In the present study, drying kinetics of jujube slices during HA and SMIR drying at 60, 70, 80 and 90 °C were investigated, quality attributes such as color, vitamin C (VC), total flavonoids content (TFC) and cyclic adenosine monophosphate (cAMP) content of dried jujube slices were evaluated. Both HA and SMIR drying process occurred mainly in the falling rate period. Drying time used in SMIR drying was 33∼83% of that in HA drying. Logarithmic model and Two-term model were the best in describing the drying process in HA and SMIR drying, respectively. Deff values of jujube slices were varied from 1.43 × 10−8 to 2.28 × 10−7 m2/s. Values of Deff in SMIR drying were two times higher than HA drying. Jujube slices dried by SMIR revealed better color, higher retentions of VC, TFC and cAMP content than HA drying. Compared with HA drying, SMIR drying showed shorter drying time, higher drying efficiency and better quality of products, indicating SMIR drying was a more promising drying method for jujube processing.

Anti-inflammatory effects of Huangqin tang extract in mice on ulcerative colitis

Ethnopharmacological relevanceHuangqinTang (HQT) is a traditional Chinese formula which is composed of Scutellaria baicalensis Georgi, Paeonia lactiflora Pall, Glycyrrhiza uralensis Fisch, and Ziziphus jujube Mill. HQT has been used in China for a wide range of disorders, especially in gastrointestinal inflammation with symptoms of nausea, vomiting, diarrhea, abdominal cramps and so on. Aim of the studyTo investigate the protective effects of HQT extract on 2, 4, 6-trinitrobenzenesulfonic acid (TNBS) induced colitis in mice. Materials and methodsDifferent doses of HQT extract (1, 2 and 4g/kg/day) and salicylazosulfapyridine (SASP, 500mg/kg/day) were administered by gavage for 7 days after the induction of colitis with TNBS. The effects were studied by macroscopic score, histological analysis, immunohistochemical study of Cyclo-oxygenase-2 protein expression, as well as by determination of inflammation markers such as myeloperoxidase (MPO) and mRNA expression levels of pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6. ResultsIn TNBS induced group, mice body weight decreased gradually and did not recover at the end of the experiment, as compared with that of control group (p<0.01). Edema and redness were also discovered in the colons profoundly and scores representing inflammation were all high in this group (p<0.01). The level of colonic MPO activity and the tissue levels of TNF-α, IL-1β and IL-6 were markedly increased (p<0.01). The mice treated with HQT extract and SASP recovered significantly compared with the TNBS group (p<0.01). ConclusionOur results suggested that the efficacy of HQT extract, especially at the higher dose, was analogous to that of SASP, which implicated its potential application as a natural alternative medicine in colitis treatment.

Ochratoxin A in Chinese dried jujube: method development and survey

A method was developed for the determination of the mycotoxin ochratoxin A in dried jujube (Zizyphus jujuba Miller) using alkaline methanolic extraction, immunoaffinity column clean-up (IAC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination. The limit of detection (LOD) was 0.01 μg kg–1 and limit of quantification (LOQ) was 0.03 μg kg–1. The average recoveries were 82%, 98% and 115% at 5, 0.5 and 0.1 μg kg–1 spiked levels with relative standard deviations (RSD) of 2.9%, 5.2% and 9.2% accordingly. The method showed good linearity for both solvent standard calibration and matrix-matched standard calibration with correlation coefficients of 0.9998 and 0.9997 respectively. The intra-day precision RSD was 3.3% and the inter-day precision RSD was 4.0%. In addition, there was almost no matrix interference in LC-MS/MS detection after the IAC clean-up process. The proposed analytical set-up was successfully used to test 20 samples that were collected from local markets and stores. The results showed that all the samples were positive and the amount of OTA ranged from < 0.01 to 0.18 μg kg–1, with a mean level of 0.14 μg kg–1. In spite of the high positive rate, samples with this level would not cause significant health effects after consumption.

Rapid SNP discovery and a RAD-based high-density linkage map in jujube (Ziziphus Mill.).

Background Ziziphus Mill. (jujube), the most valued genus of Rhamnaceae, comprises of a number of economically and ecologically important species such as Z. jujuba Mill., Z. acidojujuba Cheng et Liu and Z. mauritiana Lam. Single nucleotide polymorphism (SNP) markers and a high-density genetic map are of great benefit to the improvement of the crop, mapping quantitative trait loci (QTL) and analyzing genome structure. However, such a high-density map is still absent in the genus Ziziphus and even the family Rhamnaceae. The recently developed restriction-site associated DNA (RAD) marker has been proven to be most powerful in genetic map construction. The objective of this study was to construct a high-density linkage map using the RAD tags generated by next generation sequencing.ResultsAn interspecific F1 population and their parents (Z. jujuba Mill. ‘JMS2’ × Z. acidojujuba Cheng et Liu ‘Xing 16’) were genotyped using a mapping-by-sequencing approach, to generate RAD-based SNP markers. A total of 42,784 putative high quality SNPs were identified between the parents and 2,872 high-quality RAD markers were grouped in genetic maps. Of the 2,872 RAD markers, 1,307 were linked to the female genetic map, 1,336 to the male map, and 2,748 to the integrated map spanning 913.87 centi-morgans (cM) with an average marker interval of 0.34 cM. The integrated map contained 12 linkage groups (LGs), consistent with the haploid chromosome number of the two parents.ConclusionWe first generated a high-density genetic linkage map with 2,748 RAD markers for jujube and a large number of SNPs were also developed. It provides a useful tool for both marker-assisted breeding and a variety of genome investigations in jujube, such as sequence assembly, gene localization, QTL detection and genome structure comparison.

Identification of marker compounds for Japanese Pharmacopoeia non-conforming jujube seeds from Myanmar

Jujube seed is a crude drug defined as the seed of Ziziphus jujuba Miller var. spinosa Hu ex H.F. Chou (Rhamnaceae) in the Japanese Pharmacopoeia (JP). Most of the jujube seed in the Japanese markets is imported from China, with the rest obtained from other Asian countries. Here we confirmed the botanical origins of jujube seeds from both China and Myanmar by a DNA sequencing analysis. We found that the botanical origins of the crude drugs from China and Myanmar were Z. jujuba and Z. mauritiana, respectively. Although the jujube seed from China conforms to the JP, that from Myanmar does not. A method for discriminating jujube seeds from China and Myanmar using a chemical approach is thus desirable, and here we sought to identify a compound specific to Z. jujuba. Jujuboside A (1) was identified as a compound specific to Z. jujuba. To establish a purity test of Jujube Seed in the JP against Z. mauritiana, we fractionated the extract of Z. mauritiana seeds and identified frangufoline (2) and oleanolic acid (4) as the marker compounds specific to Z. mauritiana. Thin-layer chromatography (TLC) and gas chromatography-mass spectrometry analyses revealed that the latter compound was useful for testing by TLC analysis. The established TLC conditions were as follows: chromatographic support, silica gel; developing solvent, n-hexane:EtOAc:HCOOH = 10:5:1; developing length, 7 cm; visualization, diluted sulfuric acid; R f value, 0.43 (oleanolic acid).

대추를 첨가한 드레싱의 제조 및 품질특성

This study was conducted to develop a salad dressing using jujube (Zizyphus jujuba Miller) puree and to evaluate the processing and quality characteristics of the salad dressing containing various amounts (0, 10, 20, 30, 40, and 50%) of jujube puree. Jujube puree was prepared by crushing peeled, deseeded and steamed fruit flesh. The dressing ingredients (jujube flesh puree, soy sauce, vinegar, oligosaccharide, olive oil, and water) were mixed, homogenized, and packaged in glass bottles. The quality characteristics (color property, total titratable acidity, soluble solids, viscosity, phenolic compound content, antioxidant activity, and sensory acceptability) of the dressing were analyzed. The lightness (L*) and redness (a*) of the dressing tended to increase as the amount of the jujube puree increased whereas the hue angle (h°) decreased. The total titratable acidity, soluble solids, viscosity, phenolic compound content, and antioxidant activity of the dressing increased with the addition of more jujube puree. The sensory acceptability (color, smell, taste, texture, and overall acceptability) were significantly higher in the dressing added with 30% added jujube puree than in the other samples. The results show that jujube flesh puree (approximately 30%) can be utilized as an additive for preparing a dressing with simultaneously high antioxidant activity and acceptability.

Effects of permanent ground cover on soil moisture in jujube orchards under sloping ground: A simulation study

A simulated study including 6 soil management treatments was conducted in 2011 and 2012 to evaluate impacts of ground cover on soil moisture and slope runoff in a pear-jujube (Ziziphus jujube Mill.) orchard. Treatments were (1) strip cocksfoot (Dactylis glomerata L.) cover (SCF), (2) strip crown vetch (Coronilla varia L.) cover (SCV), (3) strip birdsfoot trefoil (Lotus corniculatus L.) cover (SBF), (4) strip white clover (Trifolium repens L.) cover (SWC), (5) full white clover cover (WCC) and (6) control (clean cultivation) (CC). Results showed that, the 2-year mean infiltration water amount after rain was significantly higher under vegetation cover treatments than under CC (P<0.05), and significantly greater under WCC than under strip vegetation cover treatments (P<0.05, except for SCF). The runoff volume and sediment yield were significantly larger under CC than under other treatments (P<0.05). The daily water consumption under WCC and CC was larger than other treatments. The mean soil moisture was significantly higher under SCF than under others (P<0.05). Significant differences were found between the grass and legume covers (P<0.05). The cocksfoot was considered as the best choice as a ground cover in pear-jujube orchards on dry slopes.

Root distribution chronosequence of a dense dwarfed jujube plantation in the semiarid hilly region of the Chinese Loess Plateau

Dense jujube (Ziziphus jujube Mill. CV. Lizao) plantations with a spacing of 2 m between trees and 3 m between tree rows have been established in the semiarid hilly region of the Chinese Loess Plateau since 1999. Our objective was to assess differences in the vertical and horizontal root distribution with stand age based on a trench wall analysis of the roots. The stands were 4, 8, and 11 years old. We investigated three root diameter classes for each stand, which consisted of fine (< 1 mm), medium (1–3 mm), and coarse (> 3 mm) roots. Our main findings were as follows. (1) All diameter classes of root intersects increased significantly with stand age (P < 0.01). However, the proportion of the three diameter classes in the total roots remained about the same, regardless of stand age. (2) Root intersects decreased significantly with soil depth (P < 0.001). (3) There were no significant differences in root intersects with distance from the trunk (P > 0.05) in this dense planting pattern. These root distribution patterns may enhance our understanding of the dense jujube plantation belowground root ecology and provide a basis for jujube plantation management practices in this semiarid hilly region.

Yields, Phenolic Profiles and Antioxidant Activities of Ziziphus jujube Mill. in Response to Different Fertilization Treatments

Increasing demand for more jujube (Ziziphus jujube Mill.) production requires understanding the specific fertilization needs of jujube trees. This study was conducted to compare fruit yields, phenolic profiles and antioxidant activity of jujube in response to different fertilizers. Application of organic fertilizer appeared to enhance the phenolics and antioxidant activity accumulation of jujubes, compared to conventional fertilized jujubes. Amongst inorganic fertilizers, supplemental potassium as an individual nutrient improved the accumulation of phenolics in jujubes. Our results demonstrate that phenolics levels and antioxidant activity of jujube can be manipulated through fertilizer management and tracked by following proanthocyanidin concentrations. In a practical production context, the combination of organic fertilizers and inorganic fertilizers such as more supplemental individual potassium, and less supplemental individual nitrogen and phosphorus, might be the best management combination for achieving higher phenolic concentration, stronger antioxidant activity and a good harvest.

Effects of drip irrigation on deep root distribution, rooting depth, and soil water profile of jujube in a semiarid region

Aims Aimed to understand how soil water was depleted by deep roots, the effects of drip irrigation and stand age on the deep root distribution, rooting depth, and soil water profile dynamics were investigated in a jujube (Ziziphus jujube Mill. CV. Lizao) plantation.

Multi-objective Optimization of Spray Drying of Jujube (Zizyphus jujuba Miller) Powder Using Response Surface Methodology

Optimum technology of spray-dried jujube powder was studied using a Box-Benhnken design. Effects of weight ratio of maltodextrin and the dry matter weight of jujube pulp (WR, 3–5), inlet air temperature (T, 140–160 °C), and shift of feed flow rate (FFR, 3–5) on the quality attributes (moisture content, lightness, the total color difference, vitamin C (VC) content and hygroscopicity) of jujube powder were systematically studied by response surface methodology and perturbation plot. Analysis of variance showed that a second-order polynomial equation could predict the experimental data well (R2 > 0.92). Moisture content and the total color difference (∆E) were significantly affected by WR, T, and FFR. The higher WR and lower FFR resulted in a decrease in moisture content and ∆E. WR and FFR had extremely significant effects on VC content and hygroscopicity (P < 0.01); with lower WR and FFR, higher values of VC content and hygroscopicity would be received. The effect of WR was the most significant variable among others. The optimum conditions that maximizing VC content and minimizing contents of moisture, ∆E, and hygroscopicity of jujube powder were found as WR of 3, inlet air temperature of 140 °C, and FFR of 3 ( i.e., 11 ml/min). Under these conditions, the response values were moisture content of 3.36 %, lightness of 83.32, ∆E of 9.92, VC content of 205.10 mg/100 g, and hygroscopicity of 18.59 %, respectively.

Chilling and heat requirements for flowering in temperate fruit trees

Climate change has affected the rates of chilling and heat accumulation, which are vital for flowering and production, in temperate fruit trees, but few studies have been conducted in the cold-winter climates of East Asia. To evaluate tree responses to variation in chill and heat accumulation rates, partial least squares regression was used to correlate first flowering dates of chestnut (Castanea mollissima Blume) and jujube (Zizyphus jujube Mill.) in Beijing, China, with daily chill and heat accumulation between 1963 and 2008. The Dynamic Model and the Growing Degree Hour Model were used to convert daily records of minimum and maximum temperature into horticulturally meaningful metrics. Regression analyses identified the chilling and forcing periods for chestnut and jujube. The forcing periods started when half the chilling requirements were fulfilled. Over the past 50 years, heat accumulation during tree dormancy increased significantly, while chill accumulation remained relatively stable for both species. Heat accumulation was the main driver of bloom timing, with effects of variation in chill accumulation negligible in Beijing’s cold-winter climate. It does not seem likely that reductions in chill will have a major effect on the studied species in Beijing in the near future. Such problems are much more likely for trees grown in locations that are substantially warmer than their native habitats, such as temperate species in the subtropics and tropics.