Feeding rhythm and growth of the tongue sole, Cynoglossus semilaevis Günther, during its early life stages

The feeding rhythm and growth characteristics of the early life stages of the tongue sole, Cynoglossus semilaevis Günther, were studied. Larvae began to prey on rotifers about 2–3 days after hatching at 23°C. About 12 days after hatching, larvae had grown to 8–9 mm in total length and were able to prey on Artemia larvae. As the larvae grew, they showed an increasing feeding capacity and a distinct feeding rhythm. Feeding intensity for day‐6 larvae was highest at 12:00 and 18:00 hours, about 2–3 h after the maximum feeding incidence. The highest levels of feeding intensity for day‐16 larvae occurred between 09:00 and 18:00 hours. By day 26, when the larvae had metamorphosed, feeding capacity had again increased considerably and, in contrast to the earlier stages, feeding intensity peaked at 18:00 and 24:00 hours concurrently with feeding incidence. Thus, tongue sole were found to have different feeding rhythms in the pre‐ and post‐metamorphosis stages, with the highest feeding activity in the daytime during the larval planktonic stage, and at night during the juvenile benthic stage. The estimated maximum daily feeding rates were 65%, 40% and 11% of body weight on days 6, 16 (larvae) and 26 (juveniles) respectively. Size variation increased markedly with development.     

不同总氮占比穗肥对水稻产量的影响

在黔东南地区进行水稻增产氮肥施用技术的田间试验,对不同总氮占比穗肥对水稻产量的影响进行了研究。结果表明,水稻孕穗期施用氮肥能使植株生长旺盛,有效穗和成穗率增加,总粒数增多,产量增加19.9-47.9kg/667m^2,增幅达3.5%-8.4%。施氮占比为15%和20%时,增产效果较好,与不施氮对照相比,差异达显著水平。但与对照相比,各处理病虫害发生略有加重,结实率略为减少,生育期稍有延长,并随着穗肥施氮占比的增加而有所加重。应根据不同气候、土壤以及产量水平,确定最佳氮肥施用总量,在孕穗期选择适宜的总氮施用比例,适当提早施用氮肥。     

黄瓜留种株光合特性的研究

以津研4号为试材,研究了黄瓜种株光合速率及其日变化。结果表明,在不同生育期内,黄瓜光合作用日变化类型不同,在黄瓜种株生长前期,叶片光合速率日变化呈双峰曲线型,有明显的"午休"现象,而在果实生理成熟期叶片光合作用日变化呈单峰曲线型,无"午休"现象;黄瓜叶腋负载果实对光合速率有明显的促进作用。     

不同生育期灌水和施氮对夏玉米生长、产量和水分利用效率的影响

【目的】研究不同生育期灌水和施氮对玉米各生育期生长、产量和水分利用效率的影响。【方法】以夏玉米蠡玉16号为试验材料,设置了7个水分处理(全生育期灌水、苗期+拔节期灌水、苗期+抽穗期灌水、苗期+灌浆期灌水、拔节期+抽穗期灌水、拔节期+灌浆期灌水、抽穗期+灌浆期灌水)和3个氮素水平(不施氮肥、低氮(60kg/hm2)、高氮(180 kg/hm2)),研究不同生育期灌水和施氮对夏玉米生长、产量及水分利用效率的影响。【结果】不同生育期灌水和施氮对夏玉米的株高、叶面积、地上部干物质、产量及水分利用效率均有一定的影响。与全生育期灌水相比,在平均氮肥(各指标3个氮素处理的平均值)水平下,苗期+灌浆期灌水处理及抽穗期+灌浆期灌水处理的株高、叶面积、地上部干物质累积量和籽粒产量显著降低,且后者的水分利用效率最低。相比较而言,苗期+拔节期灌水、苗期+抽穗期灌水及拔节期+抽穗期灌水处理玉米产量的下降幅度不大,而灌溉水利用效率却有较大提高。【结论】在试验地区,与全生育期灌水相比,苗期+拔节期灌水、苗期+抽穗期灌水以及拔节期+抽穗期灌水处理有利于维持玉米产量并提高水分利用效率,而施氮也可以显著增加玉米的产量和水分利用效率。在本试验条件下,以高氮全生育期灌水处理的产量最高。     

棉花单铃干物质积累分配的分期动态模拟及检验

 【目的】通过分期模拟不同开花期棉铃干物质在铃壳、籽棉、纤维、种子上的积累和分配，建立比棉铃干物质积累与分配的单一综合模型更实用、预测效果更好的分期模拟模型。【方法】在系统分析不同基因型、不同施肥量、不同开花期棉铃干物质积累与分配动态规律的基础上，以每日生理热效应为驱动变量，在综合考虑了氮素营养、水分胁迫、同化物供需比等对棉铃的生长发育主要影响因子的前提下，建立基于每日生理热效应的棉花单铃干物质积累与分配的分期动态模型。【结果】模拟检验结果显示，棉花四桃（伏前桃、伏桃、早秋桃、晚秋桃）单铃、籽棉、纤维干物质积累的模拟值与观察值之间的均方差根（RMSE）分别为0.1767～0.5659、0.0725～0.5279、0.0613～0.2634 g，而单一综合模拟模型的RMSE值超过或接近分期模拟模型相对应的RMSE值的上限。【结论】分期模拟棉铃干物质的积累与分配比单一综合模拟模型预测效果要准确、可靠。     

关于新对虾属Metapenaeus幼体发育分期的探讨

新对虾属Ｍｅｔａｐｅｎａｅｕｓ为对虾科Ｐｅｎａｉｄａｅ中的重要类群，随着养虾业的发展，新对虾越来越受到重视。在人工育苗中，虾类幼体发育分期对指导生产有现实意义。国外学者Ｍ．Ｓ．Ｍｕｔｈｕ等（１９７８）对近缘新对虾和道氏新对虾的糠虾（Ｍｙｓｉｓ）阶段分为５期，并在第Ⅴ期糠虾幼体之后增加两个中间期，形成Ｎ－Ｚ－Ｍ－Ｉ的“６－３－５－２”模式。作者在中型新对虾的幼体变态实验观察中注意到，糠虾幼体在一次蜕皮后其体长和附肢形态均有渐微的变化，这种形态上的细微差异不宜作为分期的依据，幼体分期的主要依据以蜕皮为标志。因此新对虾属的幼体发育分期可借鉴中国对虾（Ｐｎｕａｅｕｓｏｒｉｅｎｔａｌｉｓ）幼体分期模式划分，即Ｎ－Ｚ－Ｍ为“６－３－３”。     

The potential for advective exchange of the early life stages between the western and eastern Baltic cod (Gadus morhua L.) stocks

In order to clarify mechanisms influencing the reproductive success of Baltic cod (Gadus morhua L.), a modelling exercise was performed to examine the effects of the wind‐driven circulation on the transport of early life stages between the western and eastern Baltic. Because the different stocks spawn in different areas and environments at different times of the year, the occurrence of variable age/length distributions of juveniles within the different potential nursery areas can be explained by the circulation pattern. A three‐dimensional circulation model of the Baltic was utilized to investigate the temporal evolution of egg and larval distributions of the western Baltic cod stock, which spawns preferentially in the Danish Straits, in Kiel Bay as well as in Mecklenburg Bay. For different scenarios (1988 and 1993), within‐ and between‐year variability of egg and larval transport showed large differences, primarily due to variations in wind forcing. In 1988, relatively low and variable wind forcing prevailed, whereas, due to sustained strong, mainly westerly, winds, in January 1993, the recent major Baltic inflow to the Baltic Sea occurred. Differences in contributions of early life stages from the western to the eastern cod stocks, depending on the physical forcing conditions, suggest that this process can be controlled by variations of atmospheric forcing conditions. The potential for early life stages from the western Baltic cod stock to drift into the Arkona Basin and the Bornholm Basin, and to contribute there to the juvenile population, has been recognized as being mainly due to strong westerly winds. During cold winters, retention of eggs, larvae and juveniles within their original spawning grounds may predominate. Transport of cod early life stages from the Øresund, as well as from the Great Belt, can occur only during periods of strong westerly winds, but significant eastwards orientated drift from Kiel Bay and Mecklenburg Bay was also evident during periods of minor westerly wind influence.     

铁皮石斛不同阶段多糖和甘露糖含量研究

以软脚红杆铁皮石斛为实验材料,参考《中国药典》（I部）标准,对其原球茎、丛生芽、瓶苗茎、炼苗茎和鲜条进行多糖和甘露糖含量的检测。结果表明：（1）软脚红杆铁皮石斛不同阶段多糖和甘露糖含量都达到了中国药典的标准。（2）软脚红杆铁皮石斛植株在不同生长阶段,多糖和甘露糖含量差异较小。（3）人工组培的石斛不同阶段中,都含有丰富的多糖和甘露糖,具有较高的营养价值;原球茎与鲜条的多糖和甘露糖含量差异虽然不大,但与鲜条相比,具有生长时间短、简单易得等优势。（4）在当今野生铁皮石斛紧缺的情况下,通过组培方式获得的铁皮石斛原球茎和丛生芽,可以弥补野生铁皮石斛资源不足的问题。     

不同生育期遮荫条件下番茄矿质氮的分配效应

光合有效辐射是影响作物生长发育、产量构成以及营养状况的重要因子。由于遮荫造成的光照强度的降低经常引起干物质积累的减少和营养状况的下降。然而，在夏季晴天中午遮荫并不总是导致营养状况的降低。该文以番茄为材料，观测了不同生长阶段(开花早期，盛花期和开花后期)夏季午间遮荫(0遮荫，40%遮荫和75%遮荫)对矿质氮在番茄各器官中的含量及其分配的影响，发现不同时期影响不同。遮荫不影响开花早期和盛花期叶片氮的含量及其分配。但开花后期，40%遮荫使叶氮含量增加，叶、茎、茬中氮的分配指数高于开花早期和盛花期，并且产量增加。这些结果表明，在某些时期中度遮荫可以克服夏天辐射过强、气温过高对番茄的不良影响，有利于改善番茄氮素营养状况和提高经济产量，在生产中有一定意义。     

美国黄松个体高生长过程研究

运用SAS软件,建立美国黄松树高生长量与树龄的间的回归方程。生长模型分析表明：14龄前美国黄松高生长缓慢;14～18龄,高生长最快;18龄后高生长速率变慢,据此,可将美国黄松的生长过程划分为“慢—快—慢”3个生长阶段,在此3阶段中,树高平均生长速度分别为0．31m／a,0．75m／a和0．56m／a,对应于不同的生长阶段,应采取相应的经营措施。