‘奥嗄二十世纪’梨自交亲和性分子机制及遗传特性研究

 ‘奥嗄二十世纪’是自交不亲和性梨品种'二十世纪'的自交亲和性花柱突变体,花粉自交不亲和性功能正常,其自交亲和性突变的分子机制及遗传特性目前仍有争议。本研究通过田间自花及相互授粉以及基因组、mRNA转录和蛋白质水平比较,分析‘奥嗄二十世纪’、‘二十世纪’及其后代S-RNase基因的存在与否、表达特性及其在后代中的遗传。结果显示,‘奥嗄二十世纪’花柱S₂-RNase基因的核苷酸序列和表达特性与其原始品种‘二十世纪’的完全一样;而S4-RNase基因信号比其原始品种‘二十世纪’的弱,而且也在花柱中正常表达(包括转录和翻译水平),但表达量低;然而在其自交亲和后代基因组中检测不到S₄-RNase基因。本研究表明,‘奥嗄二十世纪’基因组中存在花柱S₄-RNase基因,但不能遗传给后代。     

Differential tolerance to iron deficiency of citrus rootstocks grown in nutrient solution

We studied the effects of Fe deficiency on physiological parameters of citrus rootstocks grown in nutrient solution. Three 4-week old rootstocks (‘Troyer’ citrange – Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf., Citrus taiwanica Tan. and Shim., and ‘Swingle’ citrumelo – Poncirus trifoliata (L.) Raf. × Citrus paradisi Macf.) were grown in nutrient solutions with 0, 5, 10, 15 and 20 μmol Fe dm⁻³. Calcium carbonate (1 g dm⁻³) was added to all solutions to mimic the natural conditions in calcareous soils. For each rootstock, shoot length, number of leaves, and root and shoot dry weights were measured at the end of experiment. Chlorophyll concentration was estimated using a portable SPAD-502 meter calibrated for each rootstock. The amount of nutrients (P, K, Mg, Ca, Fe, Zn, Mn, and Cu) was determined in shoots. Chlorophyll fluorescence parameters (F₀: basal fluorescence; F_m: maximum fluorescence; F_v = F_m − F₀: variable fluorescence) were measured with a portable fluorimeter. ‘Troyer’ citrange rootstock was the most tolerant to Fe deficiency. These plants grew more and accumulated more chlorophyll and nutrients than the others in the presence of low levels of Fe (10 μmol Fe dm⁻³). ‘Swingle’ citrumelo plants needed 20 μmol Fe dm⁻³ in the nutrient solution to secure adequate growth. ‘Taiwanica’ orange rootstock had an intermediate behaviour, but could be distinguished from ‘Troyer’ citrange based on fluorescence parameters, since there was a variation in the basal fluorescence in the former, whereas in ‘Troyer’ citrange the basal fluorescence was not affected by the supply of Fe.     

Cloning of the S25 cDNA from ‘McIntosh’ apple and an S25-allele identification method

Summary

An S₂₅-RNase gene in the pistil responsible for self-incompatibility within the apple (Malus × domestica Borkh.) was cloned from a McIntosh cultivar. We developed an S₂₅-allele-specific polymerase chain reaction and digestion (PCR-digestion) method using specific primers and the restriction enzyme BamHI. We investigated the S-allele genotypes of 18 ‘McIntosh’ progeny.     

In vitro induction of tetraploid ginger (Zingiber officinale Roscoe) and its pollen fertility and germinability

In vitro induction of tetraploid ginger (Zingiber officinale Roscoe) and its pollen fertility and germinability were investigated. The growth of shoot tip cultures on agar MS medium containing 2.0 mg l⁻¹ BA was greater than that of similar cultures in liquid MS medium with the same BA concentration. In liquid medium, the combinations of 0.5, 1.0, or 2.0 mg l⁻¹ BA with 0.05 mg l⁻¹ NAA tended to enhance the growth of the cultures. The efficiency of tetraploid induction was assessed by treating shoot tip explants on agar or in liquid MS medium containing 2.0 mg l⁻¹ BA, 0.05 mg l⁻¹ NAA, and 0.2% (w/v) colchicine for 4, 8, 12, and 14 days. The total number of tetraploids induced on solid medium was 18, but only five in liquid medium. On both media, the colchicine treatment for 8 days gave the maximum level of tetraploid induction. Therefore, it was found that the treatment of shoot tip explants on agar medium containing 2.0 mg l⁻¹ BA, 0.05 mg l⁻¹ NAA, and 0.2% (w/v) colchicine for 8 days was the most efficient way of inducing tetraploid ginger. Induced tetraploid strains, ‘4× Kintoki’, ‘4× Sanshu’, and ‘4× Philippine cebu 1’, had higher pollen fertility and germinability than the diploid counterparts, i.e., in the diploid strains, pollen fertility ranged from 0.3 to 6.2% and the germination rate from 0.0 to 0.1%, while in the tetraploid strains, pollen fertility ranged from 27.4 to 74.2% and the germination rate from 4.8 to 12.9%.     

Seasonal changes in CO2 assimilation in leaves of five major Greek olive cultivars

Leaf CO₂ assimilation rate, stomatal conductance (g_s), internal CO₂ concentration (C_i), chlorophyll (a + b) content, specific leaf weight (SLW) and stomatal density were measured during the season, under field conditions, for five major Greek olive cultivars, ‘Koroneiki’, ‘Megaritiki’, ‘Konservolia’, ‘Lianolia Kerkiras’, and ‘Kalamon’, with different morphological and agronomic characteristics and diverse genetic background. Measurements were taken from current-season and 1-year-old leaves, and from fruiting and vegetative shoots, throughout the season, from March to November in years 2001 and 2002. CO₂ assimilation rates showed a substantial seasonal variation, similar in all cultivars, with higher values during spring and autumn and lower values during summer and late autumn. Stomatal conductance (g_s) followed similar trends to leaf CO₂ assimilation rates, increasing from March to July, following by a decrease during August and increasing again in autumn. ‘Koroneiki’ had the highest leaf CO₂ assimilation rate and g_s values (21 μmol m⁻² s⁻¹ and 0.45 mol m⁻² s⁻¹, respectively) while ‘Lianolia Kerkiras’ and ‘Kalamon’ showed the lowest leaf CO₂ assimilation rate and g_s values (13–14 μmol m⁻² s⁻¹ and 0.22 mol m⁻² s⁻¹, respectively). One-year-old leaves had significantly higher leaf CO₂ assimilation rate than current-season leaves from April to June, for all cultivars. From August and then, leaf CO₂ assimilation rate in current-season leaves was higher than in 1-year-old leaves. There were no significant differences in leaf CO₂ assimilation rate between fruiting and vegetative shoots. Total chlorophyll (a + b) content increased with leaf age in current-season leaves. In 1-year-old leaves chlorophyll content increased in spring, then started to decrease and increased slightly again late in the season. Chlorophyll content was higher in 1-year-old leaves than in current-season leaves throughout the season. Total specific leaf weight (SLW) increased throughout the season for all cultivars. Stomatal density in lower leaf surface was lowest for ‘Koroneiki’ (399 mm⁻²) and highest for ‘Megaritiki’ (550 mm⁻²). Our results showed differences in leaf CO₂ assimilation rate among the five different olive cultivars, with a diverse genetic background, ranging from 12 to 21 μmol m⁻² s⁻¹. From the five cultivars examined, ‘Koroneiki’, a drought resistant cultivar, performed better and was able to maintain higher leaf CO₂ assimilation rate, even under high air vapor pressure deficit. All cultivars had a pronounced seasonal variation in leaf CO₂ assimilation rate, affected by date of the year, depending on ambient conditions. The high temperatures and high air vapor pressure deficit occurring during summer caused a reduction in leaf CO₂ assimilation rate in all cultivars. Leaf CO₂ assimilation rate was also affected by leaf age for all cultivars, with old leaves having significantly higher leaf CO₂ assimilation rate than young leaves early in the season.     

S-allele genotypes of apple pollenizers,cultivars and lineages including those resistant to scab

Summary

We examined S-allele genotypes of ten apple cultivars and species to determine their possible usefulness as pollenizers for all apple cultivars. ‘Dolgo’ did not contain any known S-RNases encoded at the S-locus, suggesting its possible usefulness as a pollenizer for almost all apple cultivars. We also identified and confirmed the S-allele genotypes of 18 apple cultivars by polymerase chain reaction (PCR)-digestion analysis. The S-genotype of ‘Kiou’ (S₁S₇), ‘Korei’ (S₃S₂₈), ‘Korin’ (S₁S₉), ‘Kotoku’ (S₁S₂₈), ‘Kyokkou (S₇S₂₅), ‘Lobo’ (S₁S₇), ’Mahe 7’ (S₂S₇), ‘Mellow’ (S₂S₃), ‘Takahara’ (S₃S₉) and ‘Warabi’ (S₉S₂₈) were confirmed by pollination results. These cultivars seemed not to have originated from the expected seed or pollen parents or, in the case of ‘Lobo’, might have been mislabelled. Finally, we identified the S-allele genotypes of ‘Prima’ (S₂S₁₀), ‘Querina’ (S₃S₉) and ‘Yoko’ × ‘Prima’ (S₃S₁₀), which are resistant to scab.     

The influence of NaCl salinity on growth,yield and fruit quality of strawberry cvs. ‘Elsanta’ and ‘Korona’

In a 2-year field study, strawberry cvs. ‘Elsanta’ and ‘Korona’ were exposed to three different levels of NaCl salinity supplied as aqueous solutions characterised by electrical conductivities of 0.3 dS/m, 2.6 dS/m, and 5.1 dS/m. Salinity in the rhizosphere reduced plant growth by up to 44% in ‘Korona’ and 90% in ‘Elsanta’. A rather distinct cultivar difference represented the reduction in leaf area per plant of 85% in the second year of experiment in ‘Elsanta’ compared to 29% in ‘Korona’. Strawberry can be regarded as a Na⁺ excluder, because Na⁺ content of both strawberry cultivars remained below 3 mg g⁻¹ dry mass at all salinity levels. Cl⁻ content increased considerably, up to 70 mg g⁻¹ dry mass in ‘Korona’ and 80 mg g⁻¹ dry mass in ‘Elsanta’ plants. ‘Korona’ retained most of its Cl⁻ in roots and crowns, whereas in ‘Elsanta’ the maximum was detected in petioles. ‘Korona’ was able to accumulate up to 33% higher Cl⁻ content in the roots than ‘Elsanta’. Macronutrient deficiency due to NaCl salinity was not observed and in comparison to ‘Elsanta’, higher Cl⁻ content in roots of ‘Korona’ did not coincide with an impairment of macronutrient uptake. Salinity stress reduced fruit yield by up to 27% in ‘Korona’ and 64% in ‘Elsanta’. Fruit quality, characterised as taste, aroma, and texture by a consumer-type panel, decreased by more than 24% in ‘Elsanta’, but in ‘Korona’ differences were insignificant. Total soluble solids (Brix) and the ratio Brix/TA (TA, titratable acid) decreased significantly by about 20% in ‘Korona’ and 35% in ‘Elsanta’. To summarise, the ability of ‘Korona’ to retain Cl⁻ in the root system more effectively than ‘Elsanta’ resulted not only in a 41% lower leaf Cl⁻ content at the highest salinity level and a better growth under NaCl stress, but also in a relatively higher fruit yield and fruit quality.     

Foliar treatment of Mn deficient ‘Washington navel’ orange trees with two Mn sources

The objective of this study was the comparison of the effect of two Mn sources (MnSO₄·H₂O, MnEDTA) which were applied at various concentrations (0, 200, 400, 800, and 1200 mg Mn l⁻¹) to the leaves of ‘Washington navel’ orange trees in order to correct Mn deficiency.One hundred and seventy days after the foliar application of Mn solutions, the mean Mn concentrations in the leaves treated with MnSO₄·H₂O (200, 400, 800 or 1200 mg Mn l⁻¹) or MnEDTA (400, 800 or 1200 mg Mn l⁻¹) were significantly higher than those of the control leaves. Manganese sulfate (MnSO₄·H₂O) was more effective than MnEDTA regarding the improvement of the leaf Mn concentrations of the trees, when applied at equal Mn concentrations. Finally, the leaf Mn concentrations were in the sufficiency range (>25 mg kg⁻¹ d.w.), only after the application of 800 or 1200 mg Mn l⁻¹ as MnSO₄·H₂O.     

Effects of IAA and BA on development of globular,heart- and torpedo-stage embryos from cell suspensions of three grape genotypes

In order to initiate cell and embryo suspensions, embryogenic calluses derived on NN solid medium with 2,4-D and BA from petioles of in vitro grown plants of three interspecific grapevine hybrids were cultured in three versions of liquid NN medium: (1) without growth regulators, (2) 0.1 mg l⁻¹ IAA and (3) 0.5 mg l⁻¹ BA. Cell and embryo suspensions were incubated two and three times in these versions of liquid media in various combinations. Incubating suspensions two times in hormone-free media and/or with 0.1 mg l⁻¹ IAA led to formation of globular embryos in the three cultivars studied and small numbers of heart-stage embryos in ‘Podarok Magaracha’ and ‘Intervitis Magaracha’. Numerous heart-stage embryos developed in ‘Intervitis Magaracha’ and ‘Podarok Magaracha’ when the suspensions had been initiated in medium with 0.5 mg l⁻¹ BA, and in ‘Bianca’ this was achieved after two incubations in the above medium. Torpedo-stage embryos were formed after subculturing heart-stage embryo suspensions in medium with 0.1 mg l⁻¹ IAA in all study cultivars. If only small numbers of embryos of a certain developmental heart- or torpedo- stage were formed, such cell and embryo suspensions need to be repeatedly subcultured in liquid medium with specific growth regulators to enable this process.     

A comparative study of chlorophyll loss and its related mechanism during fruit maturation in the pericarp of fast- and slow-degreening litchi pericarp

Changes in the levels of chlorophyll a and b and their derivatives, and chlorophyllase activities were compared in the pericarp of ‘Feizixiao’ (slow-degreening) and ‘Nuomici’ (fast-degreening) litchis (Litchi chinensis Sonn.). Cluster bagging and growth regulators were used to regulate the degreening process of ‘Feizixiao’. HPLC analysis revealed the presence of chlorophyllide a, pheophorbide a and pheophytin a as chlorophyll derivatives in litchi pericarp. Loss of chlorophylls in ‘Feizixiao’ pericarp was slower than that in ‘Nuomici’ pericarp. The concentrations of chlorophyll a and b in the pericarp of ‘Feizixiao’ were significantly higher than those in ‘Nuomici’ during fruit maturation, whereas the chlorophyll derivatives in the former were noticeably lower than in the latter. Chlorophyllase activity increased as chlorophylls diminished. Chlorophyllase activity peaked around the colour-break in ‘Nuomici’, being much higher than that in ‘Feizixiao’. Both cluster bagging and treatment with abscisic acid (ABA, 200 mg l⁻¹) or jasmonic acid (50 mg l⁻¹) significantly decreased the chlorophyll content and increased the chlorophyllase activity and the anthocyanin level. In fruit treated with 6-benzyl aminopurine (6-BA, 100 mg l⁻¹) the degradation of chlorophylls was delayed, with concomitant decrease of chlorophyllase activity and anthocyanin level. These results imply that chlorophyllase is the crucial factor in the regulation of the chlorophyll loss in the pericarp.     

Prohexadione-calcium affects growth and flowering of petunia and impatiens grown under photoselective films

The response of petunia (Petunia x hybrida Vilm.-Andr. ‘Countdown Burgundy’) and impatiens (Impatiens wallerana Hook ‘Accent Orange Tempo’) to Prohexadione-calcium was evaluated under a clear and a far-red light absorbing greenhouse (A_FR) film to investigate the dosage effect of Prohexadione-Ca and to determine if it can overcome the flowering delay under FR deficient greenhouse environments. Prohexadione-Ca reduced stem elongation of petunia and impatiens under A_FR and clear films when applied 3 weeks after germination. Late applications were less effective. In both crops, main stem length decreased in a quadratic pattern as the concentration of Prohexadione-Ca increased. Under both films, 50–100 mg l⁻¹ Prohexadione-Ca resulted in ≈30% shorter petunia plants. Greater concentrations (500 and 1000 mg l⁻¹) resulted in excessively short plants (over 70%). Prohexadione-Ca at 100 mg l⁻¹ delayed anthesis of petunia by 8 and 3 days under the clear film and the A_FR film, respectively during less inductive photoperiods but had no effect during inductive photoperiods. In impatiens, Prohexadione-Ca at 100 mg l⁻¹ delayed anthesis over 10 days under clear or A_FR film. Greater concentrations (200 and 300 mg l⁻¹) inhibited flowering of impatiens. Prohexadione-Ca treatments significantly affected flower color development. Untreated petunia plants had dark burgundy flowers. Prohexadione-Ca treatment increased L*, a*, and C* values and decreased hue angle indicating that the flowers were faded. Flowers of untreated impatiens plants were bright orange color. Prohexadione-Ca at 100 mg l⁻¹ increased L* value and decreased a*, b*, and C* values indicating that significant petal fading had occurred. Flowers of treated plants were nearly white under both films. Although effective in height control, loss of color would be a major limitation to the use of Prohexadione-Ca on flowering crops.     

The rootstock effects on plant adaptability,production, fruit quality,and nutrition in the peach (cv. ‘Suncrest’)

In clayey and calcareous soils without a stable irrigation and fertilization system, the type of rootstock can particularly affect both the vegetative and productive properties of ‘Suncrest’ peach (Prunus persica L. Batsch) plants, and the qualitative and nutritional attributes of their fruit. The GF677 rootstock (P. persica × Prunus amygdalus) promoted the highest vegetative development, followed by Julior (Prunus insistitia). The ‘Suncrest’ on Ishtara [(Prunus cerasifera × P. persica) × (P. cerasifera × Prunus salicina)] and Barrier1 (P. persica × Prunus davidiana) had lower, but similar, plant vigour, but the latter rootstock differed in its higher production of pruned wood. The lowest adaptability to these cultivation conditions was observed for ‘Suncrest’ grafted onto Citation (P. persica × P. salicina), which showed the lowest plant development and production. For the plant yield, the ‘Suncrest’ grafted onto GF677, Julior, Ishtara, and Barrier1 were all similar. The fruit yield and both the canopy volume and pruned wood of ‘Suncrest’ grafted onto Ishtara showed a particular relationship, giving the best indices of yield efficiency and plant physiological equilibrium. Moreover, the same rootstock promoted the largest fruit size, while the smallest fruit were found on GF677 rootstock. The fruit from the Citation ‘Suncrest’ ripened 3 days early, while those from Barrier1 had a late fruit ripening. Firmness, soluble solids and the soluble solids to total acidity ratio were only affected slightly by the different rootstocks, while the total acidity of the fruit varied significantly according to rootstock; the fruit from ‘Suncrest’ grafted onto Barrier1, Julior, and Citation had the highest total acidities. The rootstock effects on the nutritional attributes of the fruit were relevant. The ‘Suncrest’ on Julior and GF677, followed by Ishtara, produced fruit with the greatest antioxidant activities and total phenolic contents. The ‘Suncrest’ on Citation and, especially, Barrier1 had reduced nutritional values of the fruit. The variations in antioxidant activities and total phenolic contents showed a positive correlation.     

Video evaluation of ethylene sensitivity after anthesis in carnation (Dianthus caryophyllus L.) flowers

Differences in ethylene sensitivity among carnation (Dianthus caryophyllus L.) cultivars were evaluated using a time-lapse video recording system. Measurement of time to petal inrolling of ‘White Sim’, ‘Nora’, ‘Chinera’, and line 64-54 flowers subjected to a range of 1–20 μl l⁻¹ ethylene showed that 10 μl l⁻¹ was the optimum concentration for sensitivity evaluation with our video system. With this system we found clear differences in ethylene sensitivity among 10 cultivars and one line. ‘Candy’, ‘Pallas’, ‘Chinera’, and line 64-54 had lower ethylene sensitivities than the other seven cultivars. Line 64-54 had the longest ethylene response time (20.6 h to start of petal inrolling). Video monitoring is a simple and accurate way of evaluating ethylene sensitivity. We have also used the system to study changes in the ethylene sensitivity of carnation flowers after anthesis. We were able to detect a shift in responsiveness to ethylene that was impossible to detect by previous methods. In the Sim-type carnation cultivars tested (‘White Sim’, ‘Scania’, ‘U Conn Sim’, and ‘Nora’), ethylene sensitivity after anthesis decreased significantly with age in both early-cut and late-cut flowers. These results clearly showed that decline of ethylene sensitivity is caused by the increasing physiological age of flowers. Ethylene sensitivity after anthesis decreased with age in normal Sim-type carnations in the same way as in long-vase-life variants such as ‘Sandrosa’.     

Methyl jasmonate and CMN-pyrazole applied alone and in combination can cause mature orange abscission

Methyl jasmonate (MJ) and CMN-pyrazole alone and in combination were applied to ‘Hamlin’ and ‘Valencia’ orange trees (Citrus sinensis (L.) Osbeck) in seven separate experiments in the 1998/1999 and 1999/2000 growing seasons to induce abscission of mature fruit for mechanical harvesting. MJ alone significantly reduced fruit detachment force (FDF) of ‘Hamlin’ oranges at concentrations of 10 mM and higher. However, MJ at 20 and 100 mM caused significant defoliation. For ‘Hamlin’ oranges, the most effective treatments were those combining 10 mM MJ and 50 mg l⁻¹ CMN-pyrazole, and 20 mM MJ and 25 mg l⁻¹ CMN-pyrazole. ‘Valencia’ oranges did not respond to 10 mM MJ treatments alone or in combination with CMN-pyrazole, and required MJ at 20 mM in combination with CMN-pyrazole to loosen this late-maturing variety to below 50 N, but excessive defoliation occurred.     

Effects of putrescine application on fruit set in ‘Housui’ Japanese pear (Pyrus pyrifolia Nakai)

In Japan, artificial pollination is practiced to improve fruit set as well as fruit size and to obtain perfect round shapes in ‘Housui’ (S₃S₅) Japanese pear and most commercial cultivars that present gametophytic self-incompatibility. The period of artificial pollination application is limited by environmental conditions and the availability of a labor force. The present study aimed to determine if pre-pollination applications of putrescine (1.0 and 0.01 mM) positively affect fruit set in ‘Housui’ after hand-pollination. During 2002 and 2003, fruit set in late pollinated flowers increased with pre-pollination putrescine applications and concentrations of 1.0 mM had a better effect than 0.01 mM. In vitro pollination tests revealed that higher pollen germination was present in the stigmas of flowers sprayed with 1.0 mM of putrescine compared to the controls. Putrescine application did not affect post-pollination ethylene production in the styles. Moreover, in the styles of non-treated flowers, an increment of putrescine content and ethylene production after pollination was found, suggesting post-pollination responses and confirming the lack of antagonism between polyamines and ethylene at least during this process.     

Varying evapotranspiration and salinity level of irrigation water influence soil quality and performance of perennial ryegrass (Lolium perenne L.)

Increasing use of recycled water that is often high in salinity warrants further examination of irrigation practices for turfgrass health and salinity management. A study was conducted during 2011–2012 in Riverside, CA to evaluate the response of perennial ryegrass (Lolium perenne L.) ‘SR 4550’ turf to varying quality and quantity of irrigation water. A modified line-source sprinkler irrigation system provided a salinity gradient (EC_w ∼0.6–4.2 dS m⁻¹) in between lines. Irrigation was scheduled in four separate irrigation zones perpendicular to the irrigation lines according to 80, 100, 120, and 140% ET_o. Changes in turf quality (R² = 0.30***), were primarily driven by the number of days that the area had been irrigated with saline water. When data were separated by irrigation amount, both time and water quality accounted for 54% and 46% of the variability (P < 0.001) in quality and cover, respectively at 80% ET_o. A model was created to quantify decline in turf quality in relationship to %ET_o replacement and salinity accumulation in the rootzone (R² = 0.57). Our results suggest that perennial ryegrass requires irrigation scheduling at 140% ET_o, irrigation water quality below EC_w ∼1.7 dS m⁻¹, and EC_e below 3.8 dS m⁻¹ to maintain acceptable quality for 442 d in Riverside, CA.     

Weather effect on thermal and energy performance of an extensive tropical green roof

This study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2 °C and air temperature at 10 cm height by 0.7 °C, with no significant effect at 160 cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9 kWh m^?2 and 0.57 kWh m^?2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484 m² green roof brought potential air-conditioning energy saving of 2.80 × 10⁴ kWh each summer, equivalent to electricity tariff saving of HK$2.56 × 10⁴ and upstream avoidance of CO₂ emission of 27.02 t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings.     

京白梨等品种S 基因型鉴定及新基因S28 和S30 的核苷酸序列分析

 根据梨S基因高度保守区C1和C3区, 设计1对引物P1和P2, 对梨品种的基因组DNA进行S基因特异扩增、克隆、测序, 并在GenBank中BLAST比较, 确定S 基因特异性片段, 对京白梨等6个供试自交不亲和品种的S基因型比对结果为: 白梨中的‘库尔勒香梨’为S₂₁ S₂₈ , ‘苹果梨’为S₁₇S₁₉ ; 砂梨中的‘台湾蜜梨’为S₁₁ S₂₂ ; 西洋梨中的‘葫芦梨’为S_a S_b; 秋子梨中的‘京白’为S₁₆ S₃₀ , ‘早梨18’为S₄ S₂₈。其中S₂₈和S₃₀为首次登录的新S 基因, 在GenBank的登录号分别为AY562394 (库尔勒香梨) 和AY876945 (京白) 。     

Analysis of rhythmic growth in holly (Ilex × meserveae) grown in controlled conditions

The influence of 24 h mean air temperature (18.3, 20.6, 23.9 and 25.8 °C) and photosynthetic photon flux (PPF; 0.6, 2.1, 3.7 and 4.7 mol m⁻² d⁻¹) on the growth cycles of vegetative growth in Ilex × meserveae (‘Blue Princess’ S.Y. Hu) was investigated. Plants propagated from top cuttings were grown in greenhouse compartments. The number of unfolded leaves was recorded continuously throughout the experiment. A modified sine function was fitted to collected data and the values for the amplitude and frequency of the growth curves were analysed. The sine function was tested as a method to evaluate the influence of climate on periodically flushing species. Both amplitude and frequency were significantly influenced by air temperature and PPF. The highest frequency of flushing was found at 23.9 °C and 3.7 mol m⁻² d⁻¹. The function resulted generally in a good fit to collected data with R² values above 0.9. Growth curves of all individual plants were categorised with respect to their growth pattern as poor synchronisation within the treatments did not allow analysis of the mean values of the growth curves.     

Inhibitory effects of riboflavin (Vitamin B2) on the in vitro rooting and nutrient concentration of explants of peach rootstock GF 677 (Prunus amygdalus × P. persica)

The effect of vitamin riboflavin (B₂) on in vitro rooting of the almond × peach hybrid clone GF 667 was studied. Riboflavin was added in five concentrations: 0 (control), 0.5, 1.0, 1.5 and 2.0 mg l⁻¹. After 4 weeks in culture, riboflavin did not stimulate adventitious rooting of the explants and rooting was very low in comparison to the control treatment. A high percentage of shoots on the rooting media containing the two highest concentrations of Vitamin B₂ had shown symptoms of chlorosis and apex necrosis.