Leaf production and curd initiation of winter cauliflower in response to temperature

Summary

In experiments in 1994 and 1995 a range of transplanting dates and thermal crop covering treatments were used to produce different environmental conditions for the growth of two Roscoff cauliflower selections ‘December/January’ and ‘March’. In 1994 non-covered plants of ‘March’ initiated on average 19 d later and with 19 leaves more than ‘December/January’. In the two seasons, covering the crops gave delays in curd initiation of up to 93 d, depending on planting date, and increased the number of leaves produced by up to 50 compared with non-covered crops. Leaf production was best described by an accumulated effective day-degree scale using day-degrees <17°C for ‘December/ January’ and day-degrees <16°C for ‘March’. This shows that both light and temperature are concerned with controlling leaf production. During the juvenile phase of growth, apex diameters expanded linearly with temperature up to a diameter of about 0.2 mm. After this there was a different response to temperature suggesting that a phase change had occurred at an apex diameter of 0.2 mm. When this occurred numbers of leaves ranged from 23 to 28. Vernalization appeared to occur most rapidly in ‘December/January’ between 12 and 16°C with an optimum at about 14°C while in ‘March’ the optimum appeared to be slightly lower than this. Any increase in time spent at temperatures in excess of 16°C delayed curd initiation.     

Temperature and development in Iris × hollandica during preplanting storage. I. Leaf initiation

Summary

Leaf initiation was examined in Dutch iris bulbs during pre-planting storage temperature treatments in the dark. The number of leaves initiated before inflorescence evocation increased with increasing temperature. The base, optimum and maximum temperature for leaf initiation were established as –0.4, 13.1 and 26.7°C respectively. The rate of leaf initiation was shown to be linearly related to temperature. The average thermal-time required for each leaf to be initiated under constant temperatures was 79°Cd but leaves initiated during the transfer temperature treatments required an average of 92°Cd. Rates of leaf initiation predicted from thermal-time equations were similar to those observed in bulbs stored at the lower temperatures (2–13°C) but rates observed at warmer temperature (17–25°C) never reached the predicted high value.     

勋章菊组培快繁技术研究

以勋章菊无菌苗叶片为外植体,以MS为基本培养基,添加不同浓度TDZ、2,4-D、IAA、IBA,研究不同浓度激素及组合对丛生芽诱导、试管苗生根的影响,并进行试管苗练苗和移栽.结果表明:最佳丛生芽诱导培养基为MS+TDZ 0.8mg/L+IBA(0.1～0.5)mg/L,诱导率达到90.0％以上.最佳生根培养基为1/2MS+NAA 0.2mg/L+IBA 0.5 mg/L,生根率达到100.0％.勋章菊的叶片是外植体的较好选择,在短期内能获得大量组培苗,移栽成活率也达到95％以上.     

A model of cauliflower curd growth to predict when curds reach a specified size

A simple model is described which predicts when curds of any specified size will be produced. The model uses a quadratic relationship between the logarithm of curd diameter and accumulated day-degrees >0°C from curd initiation. Work in controlled environment cabinets showed a linear relationship between early curd growth rate and temperature between 8°C and at least 18°C, and that the base temperature for curd growth was 0°C. Data from samples taken after curd initiation are used to predict the number of day- degrees required for the crop to reach a specified size. This requirement is then converted into a predicted date by using long-term average weather data. This prediction can be updated progressively to take account of observed weather data where these deviate from average weather. Differences between the fitted relationships for different sites, years, transplantings and cultivars are discussed and data are presented showing the results of validation of the model.     

Analysis of the Growth and Yield of Overwintered Onions

The growth of a number of onion cultivars sown on different dates during late summer in several years was assessed by regular sampling. The growth during the winter of five different winter-hardy cultivars was very similar, whereas that of Rijnsburger Bola, a cultivar normally sown in spring, was clearly slower. Sowing date was shown to affect final yield through its effect on overwintering size, which in turn influenced bulb size at harvest, the proportion of plants which bolted and the extent of winter losses. During the winter months the rate of leaf initiation appeared to be decreased to a lesser extent than the growth in dry weight, which itself was decreased less than growth in leaf area. The growth of the winter-hardy cultivars from all sowing dates and seasons was well summarized by a single linear relationship between the logarithm of plant dry weight and the accumulated day-degrees between 6° and 20°C from the day of seedling emergence. Using this relationship together with temperature records from past years it was possible to estimate the best average sowing date and the year-to-year variation in optimum sowing date. This approach may prove useful in predicting optimum sowing dates for other localities from past weather records.     

Manipulation of bolting and flowering in celery (Apium graveolens L. var. dulce). II. Juvenility

After germination, a juvenile phase of development was apparent in cvs New Dwarf White and Celebrity. During this incompetent phase, plants were not induced flower even when subjected to chilling at 5°C for nine weeks. Juvenility ended and the plants became competent to perceive chilling as a vernalization stimulus when they had initiated 17 leaves including leaf primordia in cv. New Dwarf White and between 17 and 20 leaves in cv. Celebrity. After phase transition, the level of competence was not affected by plant age. The rate of leaf initiation in cv. New Dwarf White during juvenile and competent vegetative growth related linearly to temperature, increasing between 3 and 22.8°C and then declining over the range 22.8 to 37.4°C. The first 17 leaves of celery cv. New Dwarf White had longer plastochrons of 43° Cd (>3°C) each than subsequently initiated leaves with 29° Cd for each leaf. The thermal time requirement for completion of juvenile development after radicle emergence was 731° Cd> 3°C. In cv. Celebrity the first 17 leaves required 42° Cd each for initiation.     

Effect of transplanting on the growth of muskmelons,and the redistribution of nitrogen absorbed in the nursery

Transplanting muskmelon seedlings from the nursery to the greenhouse did not reduce the rate of increase of total dry weight, leaf area, amount of nitrogen (N) or photosynthetic activity, but N content on a dry-weight base first decreased and then increased. Therefore, transplanting does not necessarily cause a decline of the growth rate of the seedlings. Such a decline may depend on the nitrogenous conditions at the time of transplanting.In an ¹⁵N labelling-experiment, N incorporated into the leaves was actively redistributed to the younger leaves, and N absorbed in the nursery period is thought to be important for growth immediately after transplanting.     

播种期和品种对早熟花椰菜植株生长及异常花球的影响

对3个早熟花椰菜品种进行播种期试验,调查花球形成时植株的生长情况、从定植到花球开始形成的时间和从定植到采收的时间、异常花球种类和发生率。结果表明,随着播种期的推迟,花椰菜植株在花球形成时的最大叶长、叶宽和株高呈明显上升的趋势,花球开始形成时的叶片数则随着播种期的延迟而呈现下降的态势。播种期对花椰菜从定植到花球开始形成的时间以及从定植到采收的时间有显著的影响。花椰菜平均花球质量随着播种期的延迟而呈现上升的趋势,并于适宜播种期达到最大,之后再次下降。花椰菜异常花球包括毛花球、夹叶球、小球、未结球等类型,其发生率和发生的种类随播种期和品种的不同而发生规律性变化。     

Influence of the environment on growth and development of chives (Allium schoenoprasum L.). I. Induction of the rest period

The effect of environmental factors on the activity of chive plants has been investigated in model experiments in growth chambers, greenhouses and in the field. The rest period of chives was induced in medium temperatures by short days. The critical day-length was about 14 h, the critical photoperiodically active light intensity about 50 lx. Light intensity in the range of 4–8 klx during the basic light period has no clear influence on the induction of the rest period, but darkness prevents it. The active temperature for the induction of the rest period ranged from over 6 to below 20° C with an optimum at 14° C. Low temperature (below 6° C) preserved, or even promoted, activity of the plants. Changing day/night temperatures act approximately like the constant mean of the day and night temperatures. The action was slightly promoted by a very high amplitude within the range 6–22° C.The necessary duration of the induction period ranged from 4 weeks for a partial, to 8 weeks for a full induction of the rest period. The induction was retarded by dryness. The inductive conditions worked out in the growth chambers agree well with those prevailing in the field during the induction period. For early leaf production in autumn, chives can be kept active by a long day or by storage at low temperature, provided that necroses at the tops of the cuts of the old leaves do not lead to objections at the market. For production of undamaged, newly grown leaves the induction of the rest period is necessary.     

The development and evaluation of techniques to predict when to harvest iceberg lettuce heads

Twenty-seven crops of iceberg lettuce, cv. Saladin, were grown in 1988 and 1989 at four sites and sampled twice weekly to study heart growth under a range of environmental conditions. The aim of the work was to develop a technique to predict when heads reached a specified weight or size. Changes in heart fresh weight were best described by a Gompertz curve using effective day-degrees from transplanting as the explanatory variable. Changes in heart diameter were best described by a logistic curve using effective day-degrees from transplanting as the explanatory variable. The accuracy of prediction of the day of maturity was tested on nine independent crops using four mechanistic models describing heart growth and four other empirical models based on the duration of crop growth from transplanting. The deviations of actual from predicted dates of maturity were smaller using the simple empirical models based on days, day-degrees and effective day-degrees from transplanting than using the more general mechanistic models based on heart fresh weight or diameter. This suggests that heart formation and growth is affected in a complex way by environmental conditions during growth.     

Initiation of early summer cauliflowers in response to temperature

Summary

Two experiments were conducted with the early summer cauliflower cvs Perfection and Gypsy. The first was in controlled environment cabinets with nine temperatures ranging from 6.3 to 22.88C. The second was in the field with three planting dates and plants grown with and without fleece cover. The experiment in controlled environments enabled a model to be developed which predicted changes in apex development through both the juvenile and curd induction phases. Both the end of juvenility and curd initiation were defined in terms of apex diameter. For cv. Perfection these were respectively 0.25 and 0.55.mm while with cv. Gypsy they were respectively 0.27 and 0.51.mm. The number of leaves produced at the end of juvenility was very different in the two experiments. When applied to the field temperatures from planting, the model predicted the end of juvenility early and therefore estimates of curd initiation were inaccurate. However, when the model was started, with the recorded apex diameter exceeding that at the end of juvenility, it predicted the day of curd initiation well. The temperatures representing the lower limit, optimum and upper limit of curd induction, were estimated to be 2.2, 9.4 and 248C for cv. Perfection and 2.9, 13.0 and 23.18C for cv. Gypsy. The results suggest that juvenility is not adequately described by number of leaves and varies considerably with growing conditions. They indicate that, under optimum conditions, curd induction only takes about six days and that the critical difference between crops is the duration of juvenility.     

Environmental control of growth and flowering of Rubus idaeus L. cv. Glen Ample

Environmental control of the annual growth cycle of ‘Glen Ample’ raspberry has been studied in order to facilitate crop manipulation for out-of-season production. Plants propagated from root buds were raised in long days (LD) at 21 °C and then exposed to different temperature and daylength conditions at varying ages. Shoot growth was monitored by weekly measurements and floral initiation by regular sampling and examination of axillary bud #5. Under natural summer daylight conditions at 60°N shoot growth was nearly doubled at 21 °C compared with 15 °C, while at 9 °C one half of the plants ceased growing and formed flower buds at midsummer. Developing shoots have a juvenile phase and could not be induced to flower before the 15-leaf stage. No significant reduction in induction requirements was found in larger plants. Plants exposed to natural light conditions from 10th August, had an immediate growth suppression at 9 and 12 °C with complete cessation after 4 weeks (by September 7). This coincided with the first appearance of floral primordia. At 15 °C both growth cessation and floral initiation occurred 2 weeks later (by September 21), while at 18 °C continuous growth with no floral initiation was maintained until early November when the photoperiod had fallen below 9 h. The critical photoperiod for growth cessation and floral initiation at 15 °C was 15 h. Plants exposed to 10-h photoperiods at 9 °C for 2–4 weeks had a transient growth suppression followed by resumed growth under subsequent high temperature and LD conditions, while exposure for 5 or 6 weeks resulted in complete growth cessation and dormancy induction. The critical induction period for floral initiation was 3 weeks although no transitional changes were visible in the bud before week 4. When exposed to inductive conditions for marginal periods of 3 or 4 weeks, an increasing proportion of the plants (20% and 67%, respectively), behaved as primocane flowering cultivars with recurrent growth and terminal flowering. It is concluded that growth cessation and floral initiation in raspberry are jointly controlled by low temperature and short day conditions and coincide in time as parallel outputs from the same internal induction mechanism.     

The effect of thermal environment,planting date and crown size on growth,development and yield of Fragaria × ananassa Duch. cv. Elsanta

Summary

The effects of environmental conditions, planting date and crown size on the timing, intensity and duration of cropping in the strawberry Fragaria × ananassa cv. Elsanta were investigated. Temperature was positively correlated with the rate of progress to fruiting whereas crown size had no effect. The first fruit reached harvest maturity after an estimated 891 day-degrees had elapsed above a base temperature of 2.9°C for waiting bed plants and 831 day-degrees above a base temperature of 2.4°C for cold stored plants. Temperature was negatively correlated with total yield, berry number and average berry weight for both waiting bed and cold stored plants of different crown sizes. Yield, berry number and average berry weight were positively correlated with crown size. The effect of temperature on the yield components appeared to be due to its effect on vegetative growth of the plants: canopy development was more limited at warmer temperatures. These results can be used to generate models to predict the effect of growth environment on cropping in strawberry.     

冬、春田间枇杷叶片光合机构的运转

冬季枇杷光合作用的最适温度低于春季,光合作用的最适叶温高于环境温度;冬季枇杷的叶绿素含量、净光合速率(Pn)、Rubisco活性、RuBP再生速率、表观量子效率(AQY)、PSⅡ最大光化学效率(Fv/Fm)、光下的光化学效率(Fv'/Fm')、光化学猝灭系数(qP)及电子传递速率较低,PSⅡ反应中心失活或破坏,细胞间隙CO2浓度与环境CO2浓度比值(Ci/Ca)、光呼吸速率与净光合速率比值(Rp/Pn)、光呼吸速率与暗呼吸速率的比值(Rp/Rd)及非光化学猝灭系数(qN)较高。这些结果说明,枇杷光合作用的最适温度与环境温度的变化相适应,低温环境是限制枇杷光合作用的重要因子;光合碳代谢和光化学反应受到低温的限制是冬季光合作用较低的重要原因;在碳代谢中光呼吸所占的比例增加和非辐射能量耗散对光合机构运转有保护作用。     

橡胶草高频再生体系的建立

以橡胶草叶片为外植体,研究了消毒时间、外源激素等因素对外植体成活率、不定芽的诱导、伸长和生根的影响。结果表明:用0.1%的升汞处理7min为最佳消毒方法,最佳的再生培养基为MS+1.5mg/L 6-BA+0.1mg/L NAA,平均诱导率为97.3%,芽伸长培养基为MS+2.0mg/L 6-BA+0.02mg/L NAA+0.4mg/L GA3,生根培养基为1/2MS+0.2mg/L NAA,生根率为100%,所获得的组培苗生长健壮且移栽成活率高,最终摸索出了橡胶草最佳的再生体系。     

结球芥菜的生长动态与叶球形成

结球芥菜自播种至叶球采收可分为发芽、幼苗、叶簇生长和叶球形成4个生长期。植株、根、外叶和叶球的鲜样质量和干样质量随生长进程均逐步增加,呈单峰曲线的增长动态。叶球的鲜样质量和干样质量分别占植株鲜样质量和干样质量的48.2%和48.8%,经济系数近0.5。生育过程中,第1~5展叶是培育幼苗和叶簇的功能叶,第5~9展叶则是叶球形成的主要功能叶。叶球形成过程中球叶数及其叶面积和质量均逐步增加,采收时叶球约有12片球叶。球叶的叶面积和质量都由外而内逐渐减少,叶球的大小和质量主要决定于最外面的6片球叶(占球叶面积的84%和叶球质量的85%),属叶重型叶球     

Cardinal temperatures and thermal requirements for germination of cineraria seed

Summary

Effects of temperature on the rate of germination, measured as the reciprocal of the time taken for half the population to germinate, were studied in cineraria cvs Cindy Blue and Cindy Dark Red. The base, optimum and maximum temperatures for germination were derived respectively as 1.6, 24.8 and 37.8°C in cv. Cindy Blue, close to T_b = 1.9, T_o = 24.5 and T_m = 38.4°C in cv. Cindy Dark Red. All seeds of each cultivar had a common base temperature but needed different thermal times to germinate. Seed of cv. Cindy Dark Red began to germinate after ca. 30°Cd compared with 35°Cd required by cv. Cindy Blue. A thermal time of ca. 50°Cd was required for half the population to germinate in each cultivar and the thermal requirement for germination fraction >0.5 was similar in both cultivars. The base and maximum temperatures for germination were similar to those determined previously for leaf initiation and flower development.     

小株型大白菜新品种京春娃3号的选育

京春娃3号是由细胞质雄性不育系CMS10152与自交不亲和系09219配制而成的叠抱型深黄心小株型大白菜一代杂种。早熟,定植后55 d(天)收获,株型小,较直立,外叶深绿色,叶球筒形,叠抱,球内叶深黄色,球高21.9 cm,球直径10.2 cm,单球质量0.7 kg,667 m2产净菜6 000~7 000 kg。抗病毒病、霜霉病和黑腐病,耐抽薹性较强,品质佳。适于密植,每667 m2可定植10 000~12 000株。已在北京、河北、甘肃、云南、湖北等地推广种植。