小麦穗、小穗及子粒差异的生理原因

本文研究了冬小麦(Triticum aestivum L)在生长发育过程中，穗、小穗及子粒等产量构成因素不均衡性的生理原因。主要是从碳氮营养角度及维管系统分布等方面对造成主茎德及分蘖穗，穗中不同部位小穗、不同粒位子粒分化发育差异的生理原因进行了探讨，得到了下主要结果。 1、主茎及一蘖、二蘖的穗下节间及穗下第二节间横切面的各性状有明显的差异。穗下节间及穗下第二节间的直径，基本组织面积、中央维管束总面积及韧皮部总面积均以主茎为最大，一蘖次之，二蘖再次之。维管束数目以主茎为最多，一蘖、二蘖顺次减少。 2、从返青到拔节期。主茎叶鞘及叶片中可浴性糖含量最高，一蘖次之，二蘖再次之。尤为叶鞘中可溶性糖含量明显高于一蘖和二蘖。拔节期后，主茎叶鞘中可溶性含量较低，分蘖中含量较高。在此时期内，主茎叶鞘及叶片中可溶性氨基酸含量较低，而分蘖中氨基酸含量较高。 3、在小花两极分化期，即从药隔形成期至抽穗期，穗不同位小穗中可溶性糖及可浴性氨基酸含量不同，基本小穗中氨基酸含量最高，但可浴性糖含量最低。上部小穗中可浴性糖含量最高，但氨基酸含量最低。中都小穗中，碳氮含量较为平衡。 4。在子粒形成期，中部小穗各子粒中可溶性糖及氨基酸含量不同。第一粒位子粒中可溶性糖含量最高，二、三、四子粒顺次减少。尤其是第四子粒中可溶性糖含量极低。第二及第四子粒中氨基酸含量较高，第一及第三子粒中氨基酸含量较低。 5、在子粒形成期，不同部位小穗同一粒位子粒中可溶性糖及氨基酸含量不同，顶部小穗子粒中可溶性糖含量最高，中部小穗子粒次之，基部小穗子粒再次之。各子粒中氨基酸含量无明显差别，子粒形成初期，中部小穗子粒中氨基酸含量较高。 6、在子粒灌浆期，初期中部结实三粒的小穗第一子粒中可溶性糖含量最高，第二子粒次子，第三子粒最少。以后各子粒中可溶性糖含量无明显差别。灌浆始期，第一子粒的干重最重。第二粒次之，第三粒最轻。从灌浆中期开始，第二粒干重逐渐赶上并超过第一粒，最终子粒干重表现为II＞I＞Ⅲ。 7、在子粒灌浆初期，不同穗位小穗同一粒位子粒中可溶性糖含量有明显差别。中部小穗子粒中可溶性糖含量最高，上部小穗子粒次之，下部小穗子粒含量最低。以后各子粒中可溶性糖含量无明显差别。在整个灌浆过程中，中部小穗子粒的干重始终保持最高，上部及下部小穗子粒干重明显地低于中部小穗子粒干重。 8、穗内部维管束分布是不均衡的，中部小穗的小穗轴中维管数目多，面积大。而顶部及基部小穗的小穗轴中维管束数量较少，面积也较小。在同一小穗中，通向小花的维管束随着花位的升高，数量越来越少，面积越来越小。但通向一、二花的维管束数量及面积较为接近，差别不明显，通向三花、四花的维管束数目明显减少，面积明显减小。通入第一、二花的维管束是独立的，均直接来自小穗轴，第三花以上的小花和二花构成串联关系。 本文最后对小麦体内碳氮营养、维管束的分布和小麦主茎、分蘖及穗内部发育不均衡的关系进行了讨论。

Fish lost at sea: the effect of soak time on pelagic longline catches

Our analyses of observer records reveal that abundance estimates are strongly influenced by the timing of longline operations in relation to dawn and dusk and soak time— the amount of time that baited hooks are available in the water. Catch data will underestimate the total mortality of several species because hooked animals are “lost at sea.” They fall off, are removed, or escape from the hook before the longline is retrieved. For example, longline segments with soak times of 20 hours were retrieved with fewer skipjack tuna and seabirds than segments with soak times of 5 hours. The mortality of some seabird species is up to 45% higher than previously estimated. The effects of soak time and timing vary considerably between species. Soak time and exposure to dusk periods have strong positive effects on the catch rates of many species. In particular, the catch rates of most shark and billfish species increase with soak time. At the end of longline retrieval, for example, expected catch rates for broadbill swordfish are four times those at the beginning of retrieval. Survival of the animal while it is hooked on the longline appears to be an important factor determining whether it is eventually brought on board the vessel. Catch rates of species that survive being hooked (e.g. blue shark) increase with soak time. In contrast, skipjack tuna and seabirds are usually dead at the time of retrieval. Their catch rates decline with time, perhaps because scavengers can easily remove hooked animals that are dead. The results of our study have important implications for fishery management and assessments that rely on longline catch data. A reduction in soak time since longlining commenced in the 1950s has introduced a systematic bias in estimates of mortality levels and abundance. The abundance of species like seabirds has been over-estimated in recent years. Simple modifications to procedures for data collection, such as recording the number of hooks retrieved without baits, would greatly improve mortality estimates.

Condition factor and length-weight relationship of Nemipterus japonicus (Bloch) off Bombay coast

Fluctuations in the K values of Nemipterus japonicus (Bloch) off Bombay coast were interpreted regarding sex, month and females maturity stage. These indicate differential growth rates in males and females. Males and females attain first maturity at 145 mm and 115 mm respectively, second maturity is attained by both the sexes at 195 mm. First spawning occurs when both are of 155 mm length and at second spawning males and females attain 215 and 205 mm of length respectively. The fish mature and breed at "O" year; the main spawning period is from August to November with peak spawning activities in October. It grows about 155 mm in first year at 12.91mm per month and about 215 mm in the second year at 5.0 mm per month on an average. Length-weight relationships for males and females are given. The rate of growth of females by weight was found to be slower below 150 mm, but faster than that of males above 150 mm specimens.

Present status and future scope of fisheries in the Andaman group of islands

The coastal area of approximately 2000 km and the water-bodies in between the Andaman and Nicobar islands are rich in fishery potential which range from 0.012-0.47 million tonnes. The fishery is dominated by catches of sardines, perches, carangids, mackerels, Leiognathus elasmobranchs, seerfish, mullets and tunas. About 2050 fishermen, with 1150 country craft, 113 mechanised boats and 1367 different kinds of nets and lines are engaged in active fishing in the island. Numerous bays, lagoons and creeks are available among the group of islands for mariculture activities. The mangroves of these islands provide feeding and nursery grounds for juveniles of penaeid prawns, crabs and finfishes.