分子运动性预测顽拗性种子麻栎离体胚轴适宜贮藏条件初探

顽拗性种子在分类上分布广泛。由于顽拗性种子贮藏特性极为特殊，对脱水和低温均十分敏感，易受损伤，所以种子寿命很短，因此在植物种质资源保存领域，顽拗性种子的保存一直被列为重点研究课题，至今仍难以找到顽拗性种子的适宜贮藏条件，或该类种子保存通行的方法，仅推测长期保存顽拗性种子种质资源最有前途的方式是超低温保存，顽拗性种子资源保存是一个世界性难题。 本文试图使用分子运动性预测顽拗性种子离体胚轴的适宜贮藏条件。选用壳斗科植物麻栎种子为实验材料。应用电子顺磁共振波谱仪和自旋标记技术，以硝基氧探针CP为标记物，检测到室温下麻栎种子离体胚轴脱水过程中分子运动性的变化。含水量0.7 g H2O/g DW至0.64 g H2O/g DW范围是细胞质粘度的转折区域，低于这个含水量区域，细胞质粘度骤然上升，推测这个区域是室温下保存离体胚轴的适宜含水量下限。 通过变温电子顺磁测定，找到离体胚轴含水量在0.43 g H2O/g DW至1.02 g H2O/g DW范围内，分子运动性的临界温度和玻璃态相变温度所在区间。根据分子运动性随温度变化规律，预测含水量为0.69 g H2O/g DW的麻栎种子离体胚轴适宜贮藏温度约为-50 ℃。 根据EPR实验结果，将胚轴脱水，并根据实验条件选择不同温度进行低温贮藏验证实验，应用颜色观测法和TTC存活力鉴定法，初步验证分子运动性理论可以应用在顽拗性种子离体胚轴的低温贮藏研究中。 本研究说明顽拗性种子资源的保存有可能通过离体胚轴的低温贮藏实现，用分子运动性预测低温贮藏的适宜条件，很可能为上述问题的解决提供了有效的技术参数。

Studies on the use of alginates in frozen fishery products

Results of preliminary studies on the use of sodium alginate as a protective coating for fishery products showed that several varieties of fishes and shell fish had better keeping qualities when coated with sodium alginate.

Estimation of maximum sustainable yield (MSY) of hilsa (Tenualosa ilisha Ham.) in the Meghna river of Bangladesh

MSY per recruit of Tenualosa ilisha in the Meghna river was predicted as 112 g per recruit at the F(msy)=0.6/yr and at T(c)=0.6/yr. But Y/R=95 g per recruit was obtained at the existing fishing level, F=1.14/yr and at T(c)=0.6/yr. Existing F level was nearly double than the F(msy) level. Fishing pressure should be reduced immediately from F=1.14/yr to F(msy)=0.6/yr. F(msy)=1.14/yr was the same at first capture, T(c)=1.0, 1.2 and 1.4/yr, and MSY could be obtained as 142 g, 162 g and 176 g per recruit respectively. It is easier to change the first capture age (Tc) rather than changing off level. So, hilsa fishery manager may adopt F(msy)=1.14/yr while age at first capture must be increased from T(c)=0.6/yr (3 cm size group) to T(c)=1.4/yr (25 cm size group), by which 1.8 times production could be increased than the present production. MSY also possible to obtain as 201 g and 210 g per recruit at F(msy)=2.0/yr and 4.0/yr at T(c)=1.7/yr and 1.9/yr respectively. Under both the situations, hilsa production could be increased 2 times than the present production. To obtain the MSY=210 g per recruit the fishing level could be increased up to F=4.0/yr at T(c)=1.9/yr (34 cm size group). Economic point of view, hilsa fishery managers may choose to obtain the economic MSY as 201 g per recruit at F(msy)=2.0/yr and T(c)=1.7yr (31 cm size group) in the Meghna river of Bangladesh.

Feeding metabolism in an Indian major carp (Catla catla Lin.) fed on different protein diets

Feeding metabolism in an Indian major carp, Catla catla fingerlings of 10.8+0.56g was investigated in a flow-through water recirculating system. The metabolic energy loss in resting metabolism and feeding metabolism were determined by the indirect method of oxygen consumption followed by multiplication by suitable oxycalorific coefficient. This was done in four metabolic chambers of a respirometer system. Ten fish fingerlings of mean total weight of 109.5, 110.4 and 112.8g/chambers respectively each in two experimental runs of three treatments a, b and c were used. The mean resting metabolic rate during unfed condition showed no significant variation in different treatments. The fish in three treatments a, b and c fed on diets containing 28, 33 and 38% crude protein had significantly different (p<0.05) post-fed SDA magnitude of 497.7, 638.7 and 735.5 mgO2/chamber/day having an equivalent energy loss of 12.68, 14.68 and 15.86 KJ respectively. The SDA co-efficient in three treatments a, b and c were 14.95, 19.00 and 22.36% respectively whereas, respiratory energy - 'R' as % of mean total ingested energy in three treatments were 26.93, 31.17 and 34.74% respectively showing a significant increase (p<0.05) with increase of protein. Feeding metabolism in an Indian major carp (Catla catla Lin.) fed on different protein diets.

Studies on smoking of eel fillets

A procedure has been worked out to (hot) smoke eel fillets. Some of the important factors such as size of the fillets, brining, pre-drying, source of smoke, smoking period, final drying have been studied. Best quality of smoked product is obtained on smoking eel fillets with a mixture of coconut-husk and sag saw-dust in 1:1 proportion for 15 hours. Optimum moisture level of the final product was fixed in the range of 30 to 35% and it had a storage life of about 8 months at room temperature.

磷脂酰甘油对光系统I的调控作用

磷脂酰甘油(PG)是光系统I(PSI)中唯一的磷脂，也是PSI重要的组成部分。在本工作中，我们通过改变PSI中PG的含量(体外重组至PG脂质体或专一性磷脂酶降解)，研究了PG对PSI的调控作用。主要结果如下： 1. 外加PG导致PSI色素的结合状态和激子相互作用发生改变。吸收光谱中，Chl a特征峰蓝移且吸收降低。低温荧光光谱中，680nm处的峰逐渐明显，F730-735 /F680的比值下降，LHCI-730激发峰蓝移。可视CD光谱中Chl a、Chl b蓝移，它们的相互作用增强;类胡萝卜素分子发生红移。 2. PSI的重组引起了PSI蛋白质结构的改变，即蛋白的α-螺旋结构增加而无序结构含量减少。同时，PSI蛋白质内部的色氨酸残基处于更极性的环境。 3. PG对PSI的电子传递的影响具有浓度效应。低浓度时可以促进PSI的电子传递活性，而在相对较高浓度时抑制PSI的电子传递。 4. PLA2的处理导致PSI中PG的缺失，抑制了PSI反应中心P700的暗还原反应，即延长了其还原所用的时间。P700的暗还原反应存在快相和慢相两相反应。PG的缺失降低了这两相反应的反应速率，抑制了电子从质体蓝素(PC)到P700+的传递。