The sustainability of the common crane (Grus grus) flock breeding in Norfolk: insights from simulation modelling

VORTEX computer simulations were used to assess the viability of a small breeding flock of common cranes, recently established in Norfolk. Investigations were also conducted on the relative impact of various management options. Raising the carrying capacity of the site had little influence on the survival of the flock. However, great improvements were associated with increases in the size of the founder flock and reductions in the mortality rates of chicks and adults. Regularly supplementing the population increased flock survival times: for a fixed total number of birds added, frequently supplementing with few birds produced the best results. Immigration from the population in continental Europe also increased persistence of the flock, and it is possible that immigration rates will improve as the British flock expands. Strategies including captive breeding, and regular supplementation of the flock, may be the most effective means of ensuring the viability of the Norfolk cranes. The potential value of simulation models in guiding management of small populations is discussed.     

Bacteria and protozoa in soil microhabitats as affected by earthworms

The effects of incorporation of elm leaves (Ulmus glabra) into an agricultural sandy loam soil by earthworms (Lumbricus festivus) on the bacterial and protozoan populations were investigated. Three model systems consisting of soil, soil with leaves, and soil with leaves and earthworms, respectively, were compared. The total, viable, and culturable number of bacteria, the metabolic potentials of bacterial populations, and the number of protozoa and nematodes were determined in soil size fractions. Significant differences between soil fractions were shown by all assays. The highest number of microorganisms was found in microaggregates of 2–53 μm and the lowest in the <0.2μm fraction. A major part of the bacteria in the latter fraction was viable, but non-culturable, while a relatively higher number of culturable bacteria was found in the macroaggregates. The number of colony-forming units and 5-cyano-2,3-ditolyl tetrazolim chloride (CTC)-reducing bacteria explained a major part of the variation in the number of protozoa. High protozoan activity and predation thus coincided with high bacterial activity. In soil with elm leaves, fungal growth is assumed to inhibit bacterial and protozoan activity. In soil with elm leaves and earthworms, earthworm activity led to increased culturability of bacteria, activity of protozoa, number of nematodes, changed metabolic potentials of the bacteria, and decreased differences in metabolic potentials between bacterial populations in the soil fractions. The effects of earthworms can be mediated by mechanical mixing of the soil constituents and incorporation of organic matter into the soil, but as the earthworms have only consumed a minor part of the soil, priming effects are believed partly to explain the increased microbial activity. Received: 7 January 1996     

Seed Development, Maturation and Storage Behaviour of Mimusops elengi L.

Mass maturity (end of the seed-filling phase) occurred at about 72 days after flowering (DAF) in developing seeds of Mimusops elengi, at which time seed moisture content had declined to about 55%. The onset of ability to germinate was detected at 56 DAF and seeds showed 98% germination by 84 DAF. Tolerance of desiccation to 10% moisture content was first detected at 70 DAF and was maximal by 84 DAF. Delaying collection by a further 14 days to 98 DAF, when fruits began to be shed, reduced seed viability, particularly for seeds first dried to 10% moisture content. Hence the best time for seed collection appears to be about 14 days before fruits shed. In a separate investigation with six different seed lots, desiccation below about 8–12% moisture content reduced viability (considerably in some lots). The viability of dry seeds (below about 10% moisture content) stored hermetically was reduced at cool temperatures (5 °C and below), and none survived storage at sub-zero temperatures. The results suggest that Mimusops elengi shows intermediate seed storage behaviour and that the optimal hermetic seed storage environment is about 10% moisture content at 10 °C, while short-term, moist, aerated storage at high (40%) moisture content is also feasible.     

千年桐花粉萌发条件筛选及储存研究

[目的]为千年桐花粉萌发及储存提供理论依据。[方法]采用单因素随机试验设计,探讨蔗糖浓度、硼酸浓度、CaCl2以及pH对花粉萌发率的影响,设计4种花粉储存的方法,研究不同方法的储存效果。[结果]在花粉萌发培养基里添加15%～20%的蔗糖、20～30mg/L的硼酸及0.05%～0.10%的CaCl2,并把pH调整到6.0～6.5有利于千年桐花粉萌发;-20℃冷冻干燥贮藏是较好的储存方法,保存10 d后的萌发率仍有25.36%。[结论]该试验解决了千年桐花粉离体萌发和储存的关键问题,具有一定的现实意义。     

HMC毒素对雄花不育及正常细胞质玉米根冠活细胞的影响

本文分析了三套(T、C、S、N)与20对(C、N)玉米同核异质系,在25℃条件下,经 C 毒素(HMC)处理3小时后,观察根冠细胞的死亡率。结果表明,C 细胞质的细胞死亡率均高于其它同核异质系。因此,C 毒素对 C 细胞质的毒害作用是特异性的,同时也为快速鉴定玉米雄花不育细胞质提供了一种新方法。     

种子热风干燥发芽率的预测

根据谷物种子发芽率损失速率的正态分布理论，建立了种子热风干燥发芽率预测的数学模型。谷物种类包括大麦、小麦、玉米、高梁和大豆。以玉米为例，重点讨论了热风温度与种子初始水分对干燥过程中种子发芽率损失速率的影响。模拟结果表明，随着热风温度的升高和种子初始水分的增大，种子发芽率损失速率将增大。     

不同成熟度花生种子发芽率及活力差异性研究

本文以8130花生品种为材料,研究了不同成熟度花生种子的发芽率、活力情况及差异性.结果表明,不同成熟度的花生种子的发芽率、活力差异极大,成熟度高的种子发芽迅速整齐,种子活力强;成熟度越低的种子发芽率和幼苗干重明显降低,种子活力低.     

金银花花粉生活力测定及贮藏研究

[目的]对不同贮藏条件下金银花花粉生活力进行测定,以期为金银花生产、科研提供参考。[方法]以金银花新鲜花粉为试材,通过I-KI染色法、TTC（氯化三苯基四氮唑）染色法、培养基萌发试验法对花粉生活力进行测定,并研究了不同贮藏条件对花粉萌发的影响。[结果]培养基中添加不同浓度的蔗糖和硼酸对花粉的萌发有促进作用,其浓度分别为150、30mg/L时花粉的萌发率最大值为75.23%和52.78%;I-KI染色法不宜用于金银花花粉生活力测定;采用TTC染色法测定金银花花粉生活力达80.46%。[结论]TTC染色法测定金银花花粉生活力相对准确且简便易行。在金银花花粉贮藏过程中低温贮藏（-80℃）好于冷藏（4℃、-23℃）,不宜常温贮藏。