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1.
Summary

Data from experiments with carrots grown in phytotrons under different day and night temperatures at two locations in Norway and three harvesting dates were treated by means of Principal Component Analysis (PCA). No effect of the single temperature amplitudes were found, the significant main effects were due to the mean temperature levels of 12 and 188C, location and harvest date. The PCA visualized the effect of mean temperature level on sensory, chemical and physical variables. Differences between the two groups were mainly caused by variation in sensory variables, the first group being characterized by high score for whiteness, sweetness, acidic taste, crispness, juiciness, glucose, fructose and root length. The other group had a high score for colour, odour, overall taste and flavour parameters, firmness, dry matter, sucrose, a and b-carotene, root weight and root diameters.  相似文献   

2.
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3.
Summary

The plug plant technique for the commercial propagation of strawberries is increasing in importance. Several factors, including the properties of the substrate, can affect plug plant quality. Tests on nine substrates containing different proportions of perlite [from 0 – 75%, (v/v)], and dark and light peat [both from 0 – 80% (v/v)], were performed using a simplex-lattice design in order to establish a model for strawberry plug plant production based not only on the single component composition of the substrate, but also on the influences of the chemical and physical properties of the substrate on plug plant quality. Notable differences in physical and chemical properties were found among the nine different substrates tested, as a consequence of the broad range of their component compositions. Substrate mixes containing medium-to-high proportions [from 60 – 70% (v/v)] of light peat and low proportions of dark peat and perlite are recommended, as these resulted in a low nutrient content, a high organic matter content, a low pH, and a low “coarseness” index, which led to high-grade plug plants with greater root and crown dry weights.  相似文献   

4.
Summary

The effects of temperature on growth, development and yield of tomato (Lycopersicon esculentum) are reviewed with special emphasis on cultivar differences. The focus is on sub-optimal temperatures, above the level where chilling injury occurs. Temperature has a large effect on all aspects of development. Leaf and truss initiation rates decrease linearly with decreasing temperature. Although these rates may be different for different cultivars their response to temperature is the same. Young plants grown at sub-optimal temperatures produce thicker leaves, so they intercept less light and therefore have a lower relative growth rate. There was no interaction between temperature and cultivar for relative growth rate and related traits. In a crop producing fruits, this aspect is less important as most of the light is intercepted anyway. At sub-optimal temperatures, fruit set is reduced as a result of poorer pollen quality. The period between anthesis and ripening of the fruit increases and, as the growth rate of the fruit at a certain developmental stage is independent of temperature, fruits become larger at sub-optimal temperature. Higher temperature leads to an increase in early yield, at the cost of vegetative growth, but may also cause a delay in later trusses. Total yield over a whole season might be equal at lower temperatures, but higher tomato prices early in the season do not make it economically profitable to reduce the temperature in the greenhouse. Short-term effects might thus be different from long-term effects. In the literature, the link between yield and whole plant growth is often missing, limiting the possibilities of studying the underlying processes that contribute to changes in yield. Breeding for cultivars with equal production at lower temperatures is hampered by the limited variation for temperature response in cultivated tomato. Therefore breeders have to look for other sources of variation, as in related wild Lycopersicon species.  相似文献   

5.
Summary

Passionfruit are grown in the tropics and subtropics where mean monthly soil temperatures at 15 cm range from about 10° to 30°C. The choice of rootstock can also influence production with most industries exploiting either the purple (Passiflora edulis f. edulis) or golden passionfruit (P. edulis tflavicarpa). We examined the relationship between shoot and root growth in purple x golden hybrid E-23 grafted onto golden passionfruit seedlings. Growth was manipulated by varying the volume of the soil available to the roots or temperature of the root zone. Shoot and root growth increased as root zone volume increased from 0.3, 1.4, 4, 12 to 24 1. Shoot weight (Ws) was correlated with root weight (WR):WS = 12.697 + 5.272 WR + 0.195 WR2 (r2 = 91%, P<0.001), with the plants allocating a smaller proportion of dry matter to the roots as root weight increased. Differences in shoot growth with pot volume were not due to changes in water or nutrient status. In the temperature experiment, the two critical root zone temperatures at 90% of maximum growth were about 20° and 35° C for vine extension, leaf area, node and leaf production, and 20° and 30°C for flower production. Leaf and stem dry weight were optimal between about 18° and 34°C, while maximum root growth occurred at 38°C. There was a weak relationship between shoot (Ws) and root dry weight (WR): Ws = ?19.346 + 24.500 WR ?1.046 WR2 (r2 = 53%, .P<0.001). Apparently, variations in shoot growth at different soil temperatures cannot be explained solely by differences in root growth. Reduced growth at 10°C was associated with lower chlorophyll concentration, stomatal conductance and net CO2 assimilation, but not lower leaf water potential. The concentration of most nutrients were lower at 10°C than at higher temperatures, but none was outside the range which would be expected to restrict growth. There appears to be a co-ordination of shoot and root growth as the soil volume available for root growth increases, whereas root temperature affects the roots and tops differently. The results of the pot volume experiment demonstrate the importance of rootstock vigour in passionfruit breeding. Productivity would be affected in cool subtropical areas with soil <20°C and in tropical areas with soil >30°C.  相似文献   

6.
Under conditions of low light intensity in winter, low temperatures (1–4°C) increase the occurrence of flower blasting. This chilling damage was observed at two developmental stages — immediately after planting and at the 7th leaf stage when spike emergence starts. Gladioli are extremely tolerant to high temperatures (up to 50 °C) as long as air humidity and soil moisture are at an optimum. The damaging effect of high temperature is generally indirect via its effect on plant water balance. Plants were directly damaged by high temperature during the period from planting to the first leaf stage. Decrease in soil moisture reduced flowering at most stages of development. The stages immediately after planting and just before spike emergence were the most sensitive.  相似文献   

7.
Summary

Rooting and growth responses of miniature rose cuttings were investigated in an experiment in which four propagation temperatures, two photosynthetic photon flux densities (PPFDs) with five auxin (IBA) concentrations, cutting sizes and cutting positions, were combined factorially in a response-surface design. Most prominently, temperature, cutting size and auxin and their interactions, influenced root and shoot growth. A propagation temperature of 24.6°C, and IBA concentrations between 10–3 and 10–1M, depending on temperature, were optimal for root formation. Root formation in extra short cuttings was delayed at low IBA concentrations. Regarding root formation, IBA could substitute for increased temperature as well as for increased cutting size. Onset of axillary bud growth was fastest at 24.6°C, and delayed in extra short cuttings. Application of IBA at 10–4 to 10–3M was optimal for axillary bud growth. By increasing the IBA concentration both time to flowering and plant height increased at 24.6°C. In cuttings from higher positions on stock plants, axillary shoots enhanced their growth to flowering, became shorter, and weighed less, suggesting occurrence of positional effects (topophysis). The growth rate increased with increasing IBA concentration, as well as from medial to low positioned cuttings. Increasing propagation PPFD from 46 to 72 µmol m–2s–1 did not affect the parameters. Time to axillary bud growth and time to first flower were related to time-to-visible root. Fast formation of roots apparently resulted in fast axillary bud growth. In time-to-visible root and axillary bud growth, the smallest variation between plants was found at optimal ranges for temperature, IBA concentration and cutting size, and further factors optimal for root formation and axillary bud growth provided the most synchronized plant development.  相似文献   

8.
Summary

To determine the chemical basis of almond flavour phenotypes, non-bitter, semi-bitter, and bitter kernels from 101 almond trees, all derived from a common maternal parent, were evaluated for flavour using three approaches: (1) sensory analysis (i.e., by taste); (2) amygdalin quantitation (using High Performance Liquid Chromatography); and (3) non-targeted analysis of volatile metabolites released on maceration (by Solid Phase Micro-Extraction, Gas Chromatography-Mass Spectrometry, and Chemical Sensor). Tasting identified three categories of flavour (non-bitter, semi-bitter, and bitter) that were also distinguishable on the basis of chemical analyses, and by a chemical sensor using principal component analysis. Highly significant correlations were found between amygdalin content and the taste panel’s score for ‘marzipan’, and also between the taste panel’s scores for sweet and overall taste preference. Non-targeted metabolite analysis identified benzyl alcohol and 2,3-butanediol as potentially important flavour components of almond, for the first time.  相似文献   

9.
Summary

Ethephon (2-chloroethylphosphonic acid), an ethylene-releasing agent, is used in the production of Summer-to-Autumn-flowering chrysanthemums (Chrysanthemum morifolium Ramat.) to avoid early budding under long-day conditions. This study was carried out to show the variation in response to ethephon due to temperature, season, and cultivar. The seasonality of growth and flowering capacities, growing temperatures, and the genetic background of chrysanthemum make the effects of ethephon unstable and variable. The most important factor modifying the effect was the response to temperature, which showed seasonal variation. Ethephon briefly suppressed extension growth and flowering after chilling and at high growing temperatures. On the other hand, it induced dormancy and rosette formation, and suppressed flowering after Summer, and at lower temperatures. This suggests that ethylene is involved in the induction of dormancy.  相似文献   

10.
The effect of light intensity, temperature and CO2 concentration on anthocyanin content, blueing of flowers and size of flower buds was examined in ‘Baccara’ roses. Reflectance percentage at 425 nm was found to be an accurate measure of petal blueing. Reflectance was higher as the degree of blueing (determined by subjective estimation) increased and pigmentation decreased. During the first stage of development of the flower branch (elongation stage) temperature and light intensity had no effect on blueing. During Stage 2 of development (main stage of bud development), high temperatures and low light intensities caused blueing, whereas low temperatures during this stage, even at low light intensities, prevented blueing. Blueing was associated with low concentrations of CO2 (0–100 vpm) as well as darkness. High concentrations of CO2 (1500–3000 vpm) prevented blueing and increased pigmentation and flower size. The effectiveness of CO2 in preventing blueing is related to high light intensities.  相似文献   

11.
以25个新疆甜菜品系（种）为材料,对块根8个主要农艺性状进行变异系数、相关性和主成分分析。结果表明：根头长度的变异系数较大为29.14%,根宽的变异系数最小为7.86%。在相关性上,糖甜菜根宽、根颈周长、根头长与根重呈极显著正相关;甜菜含糖率与根体长度呈极显著的正相关。主成分分析结果表明,前3个主成分对含糖率变异的累计贡献率达到85.21%,对根重变异的累计贡献率达到88.53%。首先对变异大的性状进行选择是非常重要的,在含糖率性状选择上,应注意选择根颈长度、根颈周长、根体长度大,根沟较深的品系（种）。在根重性状选择上,应注意选择根宽、根颈周长、根颈长度大,根沟较浅的品系（种）。  相似文献   

12.
Summary

The effects of heat injury induced by long exposures were evaluated in strawberry (Fragaria × ananassa ‘plants’) Camarosa in this study. Seedlings were grown in 14 × 12 cm pots using perlite for three weeks at 25/10°C day/night temperature, and watered daily by modified 1/3 Hoagland nutrient solution. Half of the plants were transferred to a growth chamber with a constant 25°C, 16/8 h (light/dark) photoperiod regime and 1200 lux light intensity for a week to acclimate the plants. Temperature was increased stepwise (5 K per 48 h) to 30, 35, 40°C and finally to 45°C. In addition to others, plants were transferred from the outside to the growth chamber, at each temperature step to impose a heat shock. Leaf relative water content (RWC, %), loss of turgidity, chlorophyll content (Spad value) and heat-stress tolerance (HTS; LT50) were measured in control and stressed plants. Total soluble proteins and total DNA were extracted from the leaves following the above treatments using standard procedures and total protein contents were determined using a Bradford assay. In general, effects of gradual heat stress (GHS) and shock heat stress (SHS) on the variables studied were mostly significant, except for chlorophyll content, while the effect of temperatures was significant for all the variables. Interaction between the heat stress type and temperature treatments was not significant for leaf RWC, loss of turgidity and chlorophyll content. Data also indicated that total protein and DNA contents were changed significantly by heat stress types (GHS and SHS) and/or temperature treatments. The plants exposed to GHS exhibited a significant increase in HST compared with the plants exposed to SHS (LT50 of 41.5°C and 39°C, respectively). Consequently, gradual heat stress increased HST in strawberry leaves. Increased HST may be associated with the accumulation of several heat-stable proteins in GHS plants.  相似文献   

13.
Management may influence abiotic environments differently across time and spatial scale, greatly influencing perceptions of fragmentation of the landscape. It is vital to consider a priori the spatial scales that are most relevant to an investigation, and to reflect on the influence that scale may have on conclusions. While the importance of scale in understanding ecological patterns and processes has been widely recognized, few researchers have investigated how the relationships between pattern and process change across spatial and temporal scales. We used wavelet analysis to examine the multiscale structure of surface and soil temperature, measured every 5 m across a 3820 m transect within a national forest in northern Wisconsin. Temperature functioned as an indicator – or end product – of processes associated with energy budget dynamics, such as radiative inputs, evapotranspiration and convective losses across the landscape. We hoped to determine whether functional relationships between landscape structure and temperature could be generalized, by examining patterns and relationships at multiple spatial scales and time periods during the day. The pattern of temperature varied between surface and soil temperature and among daily time periods. Wavelet variances indicated that no single scale dominated the pattern in temperature at any time, though values were highest at finest scales and at midday. Using general linear models, we explained 38% to 60% of the variation in temperature along the transect. Broad categorical variables describing the vegetation patch in which a point was located and the closest vegetation patch of a different type (landscape context) were important in models of both surface and soil temperature across time periods. Variables associated with slope and microtopography were more commonly incorporated into models explaining variation in soil temperature, whereas variables associated with vegetation or ground cover explained more variation in surface temperature. We examined correlations between wavelet transforms of temperature and vegetation (i.e., structural) pattern to determine whether these associations occurred at predictable scales or were consistent across time. Correlations between transforms characteristically had two peaks; one at finer scales of 100 to 150 m and one at broader scales of >300 m. These scales differed among times of day and between surface and soil temperatures. Our results indicate that temperature structure is distinct from vegetation structure and is spatially and temporally dynamic. There did not appear to be any single scale at which it was more relevant to study temperature or this pattern-process relationship, although the strongest relationships between vegetation structure and temperature occurred within a predictable range of scales. Forest managers and conservation biologists must recognize the dynamic relationship between temperature and structure across landscapes and incorporate the landscape elements created by temperature-structure interactions into management decisions.  相似文献   

14.
Tree planting has been favoured in many North American cities, including Montreal which aims to increase its canopy from 20% to 25% in 2025. However, the mortality rate of street trees is especially high in the first few years after planting. Studies have shown that variables that are intrinsic to the tree and those related to its location, the urban form and the socio-demographic characteristics of the surrounding environment are significantly associated either with trees’ survival rate or with vegetation cover. In this research we examine variables that have statistical associations with tree growth, which is the diameter at breast height divided by the number of years on the ground, for approximately 28,000 street trees in Montreal. Independent variables were nested into three spatial scales: the tree (species and physical variables), the street section (urban form variables), and the census tract (socio-demographic variables). Multilevel models reveal that 65.51% of the growth variance is potentially explained by the species and planting physical conditions such as the east and north sides (positive associations with the growth), signage as an obstruction (negative association). 28.54% of the grow variance is potentially explained by the urban form, in our case building age (convex relationship with the growth), mixed zoning (negatively) and residential zoning (positively). At the neighbourhood level, although none of our variables is significant, 6.95% of the growth variance is be potentially explained by other missing variables. New planting programs should hence consider the urban form in order to improve tree growth.  相似文献   

15.
Summary

Models to simulate the induction of the “bracting” and “riciness” defects in cauliflower were estimated from field experiments. Bracting, where small cauline leaves develop and penetrate the curd surface, is caused by high temperatures – a kind of de-vernalization. Riciness, on the other hand, where small flower buds develop on the curd surface, is caused by low temperatures, especially after a preceding period of high temperature – a kind of strong vernalization. Both bracting and riciness can be induced only at certain stages during plant development. Plots of cauliflower were given periods of different temperature treatments in the field by portable compartments with both cooling and heating units. The treatments were both constant high or low temperatures (24, 18, 13 and 8°C) in 10 d periods, and alternating high and low temperatures (23/23, 23/15, 23/10 and 23/5°C) in 7 d periods. The treatments were started both before and after curd induction. The incidences of bracting and riciness in harvested curds were recorded in 84 plots with different temperature regimes. These data were used to estimate the combined effect of plant development and temperature on quality defects. The responsive developmental stages in the plants were described by a parabolic function, which depends on the apex/curd diameter. The curd diameter with the highest risk of induction of bracting was estimated to be around 12 mm (range 1–23 mm). A combined model of the diameter function and the summation of daily average temperature with a base temperature of 15°C explained 66% of the variation in the data of observed bracting. The apex diameter with the highest risk of induction of riciness was estimated to be around 0.35 mm (range 0.2–0.5 mm). A combined model of sensitive apex diameter and the preceding temperatures (average daily temperature of 10 d), during a temperature drop (average minimum temperature of 10 d), and after (average daily temperature of 6 d) explained 71% of the variation in the data of observed riciness. These models may be used to set up test equipment and to test susceptibility of new cultivars in breeding programmes. On a farm level, the models may be used to forecast risk of quality defects in cauliflower production. Alternatively, the knowledge of how the combination of developmental stage and temperature scenario induce either bracting or riciness may be used to study flower induction by temperature.  相似文献   

16.
须晖  张瑶  王蕊  李天来  刘冰 《中国蔬菜》2010,1(14):26-30
通过光照培养箱准确控制光温环境,对不同温度、光照强度和CO2浓度环境因子组合条件下的甜瓜苗期叶片净光合速率的连续测定,并通过单因素相关性分析温度、光照强度和CO2浓度对叶片光合作用的综合作用。结果表明:在光照强度600μmol·s-1·m-2一定的条件下,温度在12～30℃范围内,叶片净光合速率与温度呈正相关,且在30℃时达到最大值;温度在30～36℃范围内,净光合速率与温度呈负相关;固定CO2浓度为1000μL·L-1,光照强度在70～600μmol·s-1·m-2之间,净光合速率与光照强度呈正相关;在温度一定的条件下,CO2浓度在400～1600μL·L-1范围内,净光合速率与CO2浓度具有很好的正相关性。  相似文献   

17.
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18.
在不同温度、光照、贮藏条件、浸种处理下研究水罗伞种子的发芽特性,比较3种不同基质下的种苗生长发育情况。结果表明:光照条件对水罗伞种子萌发的影响不明显,当温度在15/25℃及25℃时种子具有较高的发芽率,浸种24h发芽率最高可达到96.7%,室温下贮藏60d后种子发芽率明显下降。3种不同播种基质间种子发芽率没有明显差异。随着苗木的生长,播种180d后调查显示,以疏松而富有营养的泥炭土条件下其根长、根重、全株重值均最大,苗木生长最好。  相似文献   

19.
A total of 694 streams were sampled for benthic macroinvertebrates in the autumn of 1995 as part of the Swedish national stream survey. After removal of sites considered as impacted, data from 428 streams as well as a large number of environmental variables were used to determine the relative importance of local, landscape, and large scale factors in explaining the variability in species composition of benthic stream macroinvertebrates. The environmental variables were divided into seven explanatory variable groups: local physical, local chemical, catchment land use/cover, catchment bedrock geology, Quaternary geology in catchment, regional factors (such as ecoregion) and spatial position. Partial Canonical Correspondence Analysis was used to partition the total explained variance in the species data into these variable groups. The pure (or unique) effects of the seven variable groups accounted for 69.1%, and combinations of variable groups (interaction terms) the remaining 30.9% of the total explained variability. Local scale variables such as in-stream substratum, vegetation in and near the stream (riparian zone), and some chemical variables were most strongly associated with the among-site variability. Local physical (24.4%) and local chemical (20.4%) variables explained the largest part of the among-site variability of community assemblages. These results are of importance when planning conservation and management measurements, implementing large-scale biomonitoring programs, and predicting how human alterations will affect running water ecosystems.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   

20.
The effect of a wide range of soil temperatures (6–26°C) on growth and flowering of Chrysanthemum morifolium Ram. ‘Horim’ were studied at the favourable air temperature of 18°C. Shoot growth was severely reduced at soil temperatures below 10°C which may be explained by poor root growth, while flowering was enhanced by approximately 2 days compared to higher soil temperatures. Increasing the soil temperature to 18°C was beneficial. Further increase had no positive effect on growth. Measurements of net photosynthetic rates revealed no effect of lowering soil temperatures from 18 to 6°C.Mother plants grown at 18°C air temperature revealed no effect of soil temperatures ranging from 13 to 21°C on number and fresh weight of the cuttings. Neither did mother plants grown at the less favourable air temperatures of 12 or 15°C. Cutting production was, however, affected by air temperature.  相似文献   

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