喷施磷酸二氢钾对桃叶片和果实性状的影响

以不同成熟期的桃品种豫甜、豫香、秋甜、秋蜜红为试材,研究了喷施磷酸二氢钾对其叶片叶绿素含量、干鲜质量比及果实的可溶性固形物含量、可溶性糖含量、可滴定酸含量、维生素C含量等品质特性的影响。结果表明,喷施磷酸二氢钾能提高叶片中叶绿素含量、干鲜质量比和果实可溶性固形物含量、可溶性糖含量;对果实的可滴定酸含量、维生素C含量影响不明显;叶片喷施不同浓度和次数的磷酸二氢钾均可推迟桃果实成熟期;喷施清水和对照处理间叶片性状和果实品质差异不明显;喷施磷酸二氢钾浓度和次数以500mg/L3次效果最显著,以300mg/L3次最经济有效。     

低温胁迫对温州蜜柑光合作用的影响

低温处理使温州蜜柑叶片的气孔导度、净光合速率、光合表观量子效率及光合作用的光饱和光强和ＣＯ２饱和浓度降低,细胞间隙ＣＯ２浓度、光补偿点和ＣＯ２补偿点提高。虽然１０℃处理植株数小时后即出现光合速率下降,但叶绿素荧光测定结果显示,只有在３℃低温处理后,反映光系统Ⅱ光化学效率的Ｆｖ／Ｆｍ比值和Ｔ１／２才有较明显下降,而Ｆ０则明显升高。低温在３０～４０μｍｏｌ·ｍ－２·ｓ－１弱光下对光合的影响明显大于黑暗下。     

Comparative Study of Nutrient Deficiencies on Growth and Photochemistry of Tobacco

Abstract

Element deficiencies, such as molybdenum (Mo), iron (Fe), calcium (Ca), lead to disturbances of morphological and physiological processes of tobacco (Nicotiana tabacum L.). On exposure to nutrient solution without Mo, leaf morphology was significantly affected, whereas photosynthetic processes conserved their normal activities. The decreased Mo, Fe, and Ca concentrations in tobacco were associated with loss of pigments and photosynthetic disturbances. In Ca‐deficient plants a reduction in the rate constant of energy trapping by PSII centers and a physical dissociation of LHC from PSII core, were observed. The poisonous action of Fe and Ca deficiencies focused mainly in the decreased proportion of active chlorophyll associated with the reaction center (RC) of PSII (decreased F _v /F ₀) and in the declined total number of electrons that have gone through the RCs (decreased Area/F _m  ? F ₀). In parallel, the non‐photochemical quenching coefficient was significantly enhanced in Fe and Ca‐deficient plants, but remained unchanged in Mo‐deficient plants. It is obvious that nutrient deficiency may trigger some protective mechanisms in order to PSII could maintain its activity under that type of stress.     

Effects of fruit bagging on coloring and related physiology,and qualities of red Chinese sand pears during fruit maturation

Red Chinese sand pears (Pyrus pyrifolia Nakai) are particular to China. In order to determine the effects of fruit bagging treatments (including bag types, bag removal patterns and dates) on fruit qualities and to understand the mechanism of coloring of red Chinese sand pears, two experiments were carried out. In the first experiment, fruit of ‘Meirensu’ were firstly covered by light-impermeable paper bags with different levels of light permeable liners during their early development stage, then, the whole bag were/not removed or only the outer layer of bags were removed 3, 2 or 1 weeks before harvest. Thus, the fruit were/not totally re-exposed or were under different levels of sunlight transmission (80.31% or 34.71%). Non-bagged fruit were used as the control. Bagging treatments significantly affected the concentration of anthocyanin and the visual qualities of pear fruit. Compared to control, fruit re-exposed totally for 2 or 3 weeks accumulated the largest amount of anthocyanin and fruit receiving 80.31% and 34.71% of sunlight for 1–3 weeks could synthesize a little anthocyanin, indicating that high light intensity is imperative for coloring in red Chinese sand pears. Bagging treatments did not affect contents of total soluble sugars, but decreased organic acids contents in fruit. In the second experiment, fruit of ‘Meirensu’ and ‘Yunhongli No. 1’ were covered with only one type of light-impermeable bag during the early development stage and totally re-exposed after the bag removal 15 days before harvest. Fruit were then collected at different intervals to trace the time-course of coloring, and related physiology and inner qualities. With increasing time after the bag removal, the concentration of chlorophyll, carotenoid, flavonoid and total phenols changed little, but the concentration of anthocyanin accumulated extremely fast within 10 days after the bag removal in both cultivars and thereafter kept constant. ‘Yunhongli No. 1’ had higher anthocyanin contents and lower hue angle than ‘Meirensu’, indicating a higher potential of anthocyanin synthesis. After the bag removal, the sucrose contents and PAL activities increased gradually and correlation analysis revealed that they were highly correlated with anthocyanin accumulation in two cultivars. This study suggests that anthocyanin biosynthesis in red Chinese sand pears is a highly light dependent process and modified by genotypes. Based on the current results, in order to obtain red Chinese sand pear fruit with attractive appearance and good inner qualities, fruit must be covered with light-impermeable bags at the early stage of fruit development and the bag should be removed totally at least 10 days before harvest.     

采后乙醇处理对萝卜幼苗延迟衰老作用的影响

去根小萝卜幼苗，放置在０．５Ｌ的塑料盒中，用０．０５－１．０ｍｌ不同量的乙醇处理不同的时间，４ｄ后测定叶绿素损失量，氧的消耗量，二氧化碳产生量。结果发现，经乙醇气处理后的样品组，叶绿素损失均比对照组明显减少，二氧化碳生成量和氧的消耗量也比对照组显著降低，说明呼吸作用减缓并受到了抑制，延迟了衰老作用的发生。     

Photosynthesis,Chlorophylls, and SPAD Readings in Coffee Leaves in Relation to Nitrogen Supply

The export of nitrogen (N) from senescent plant parts is important for the efficient use of this macronutrient. The objective of this study was to establish correlations among the photosynthetic pigment content, total N, and the photosynthetic variables with the SPAD‐502 readings in Coffea arabica leaves. Correlations were established among the chlorophyll content, N content, and chlorophyll a and b with SPAD‐502 readings taken on coffee leaves at different months. The results show that all variables decreased with time. However, correlation increased linearly with N doses. Total chlorophyll presented a direct linear correlation with readings of the portable chlorophyll meter. The SPAD readings have shown to be a good tool to diagnose the integrity of the photosynthetic system in coffee leaves. Thus, the portable chlorophyll SPAD‐502 instrument can be used to evaluate the N status and can also help to evaluate the photosynthetic process in coffee plants.     

Effect of Soil Moisture on Relative Leaf Water Content, Chlorophyll, Proline and Sugar Accumulation in Wheat

The responses of four wheat ( Triticum aestivum L.) varieties to soil moisture were determined by measuring plant parameters such as relative leaf water content (RLWC) and the chlorophyll, proline and sugar contents of the leaf over two seasons. Two levels of irrigation treatments were adopted: irrigated and rainfed. The rainfed plants had consistently higher amounts of proline and sugar but lower RLWC and chlorophyll content. As drought intensified, differences between the irrigated and the rainfed plants with respect to all of these characters increased. The RLWC values of the irrigated plants were significantly higher in the morning but lower values were found at noon, showing some recovery in the afternoon.     

Photosynthetic Apparatus Responses to Short‐term low‐temperature Flooding May Contribute to Freezing Tolerance Changes in Forage Grasses

Winter conditions are subjected to rapid climate changes. Increased precipitation and snow melting during warmer winters may result in low‐temperature flooding. These factors probably affect plant overwintering strategies. This study investigated the relationships between the photosynthetic adjustment and freezing tolerance following a short‐term low‐temperature flooding in two forage grasses (Lolium perenne and Festuca pratensis). The effect of flooding on the photosynthetic apparatus acclimation to cold was determined using chlorophyll a fluorescence measurements. Freezing tolerance was estimated using an electrolyte leakage test. It has been shown that genotypes activating non‐photochemical mechanisms of photosynthetic acclimation to cold during low‐temperature flooding may show increased freezing tolerance. Freezing tolerance reduction observed in Festuca pratensis was probably connected with decreased photochemical activity and photoinhibition of photosynthesis. It can be concluded that photosynthetic apparatus response to low‐temperature flooding may contribute to changes in the freezing tolerance. The direction of the changes is associated with different photosynthetic apparatus performance.     

Direct non-thermal plasma treatment for the sanitation of fresh corn salad leaves: Evaluation of physical and physiological effects and antimicrobial efficacy

Current problems with outbreaks of serious infections caused by human pathogens on fresh-cut greens highlight the need for new, optimized postharvest sanitation treatments to effectively meet recent food safety standards. In contrast to various chemical treatments, non-thermal plasma (NTP) has a high potential as a gentle target sanitation technique. However, possible interactions between NTP and the physiology of treated fresh products have not been investigated in detail. Here, chlorophyll fluorescence image analysis (CFIA) was used to study the potential impacts of non-thermal plasma on the photosynthetic activity of highly perishable corn salad leaves as a model produce. For this purpose, an atmospheric pressure plasma jet, driven at radio frequency, and transforming argon with flow rates of 20 L min⁻¹ into non-thermal plasma at 10, 20, 30, and 40 W generator power was applied for various times to the surface of corn salad leaves. Thermographic measurements indicated maximum temperatures of 39.0 °C, 44.4 °C, 60.1 °C, and 66.0 °C, respectively, on treated leaf surfaces. CFIA revealed that treatment at moderate generator power of 20 W for up to 1 min was the maximum setting for quality retention. Furthermore, the microbial inactivation efficiency of the plasma jet system at these operating parameters was successfully tested on Escherichia coli bacteria, inoculated on corn salad surface at 10⁷ cfu cm⁻² and 10⁴ cfu cm⁻². At 20 W, bacteria with lower initial load could be inactivated by 3.6 (±0.6) log-cycles within 15 s of treatment duration; whereas at the higher initial load of 10⁷ cfu cm⁻², bacteria were reduced by 2.1 (±0.2) log-cycles after 30 s.     

西葫芦银叶病发病叶片叶绿素代谢及其荧光特性

 研究了西葫芦银叶病发病叶片和叶柄叶绿素代谢特性和叶片叶绿素荧光参数的变化。与对照相比，发病叶片和叶柄叶绿素总量(Chl.a+b)，叶绿素a (Chl.a)，叶绿素b (Chl.b)含量均下降；轻度与重度发病叶片叶绿素a/b增加，中度发病叶片与对照差异不显著，而叶柄比对照降低。西葫芦银叶病对叶片Chl.b的影响比Chl.a大，而对叶柄Chl.a的影响比Chl.b大。发病叶片和叶柄叶绿素酶活性升高，从而使叶绿素降解加速，叶绿素合成中间产物Protoporphyrin IX (Proto IX)，Magnesium protoporphyrin IX (Mg-Proto IX)，Protochlorophyllide (Pchlide)含量降低，Uroporphyrinogen Ⅲ (Uro Ⅲ)含量增加，表明叶绿素合成在 Uro Ⅲ到 Proto Ⅸ受阻。发病叶片最大光化学量子产量(Fv/Fm)，光系统Ⅱ(PSⅡ)的潜在活性(F_v/F_o)，实际光化学效率(φPSⅡ)，光化学淬灭系数(q_P)降低，非光化学淬灭系数(NPQ)增加。试验结果表明，西葫芦银叶病破坏了叶绿素合成和降解的动态平衡，叶绿素合成受阻和叶绿素降解加速是导致叶片叶绿素含量降低的原因；发病叶片叶绿体PSⅡ活性受到抑制。