不同处理对多叶羽扇豆种子发芽的影响

采收不同成熟度的种子,分别阴干、晒干和0 ℃保藏0、54和84 d,研究其发芽率和发芽指数。结果表明,湿种子比阴干和晒干种子的发芽率和发芽指数高,差异极显著;阴干的红、紫品种褐色湿种子比褐色干种子、黄色湿种子和绿色湿种子发芽率和发芽指数高,白色品种黄色湿种子比褐色干种子、绿色湿种子和褐色湿种子发芽率和发芽指数高;0 ℃保藏0、54、84 d对红色多叶羽扇豆种子发芽率和发芽指数无明显影响。     

Ultrastructural analysis of the loss of desiccation tolerance in germinating Eremanthus erythropappus seeds

Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and dispersed at the end of dry season.This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed.This study evaluates if the damages caused by drying of germinating E.erythropappus seeds,at the stage when they have lost desiccation tolerance,are lethal.The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated.Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion(approximately 72 h)when the radicle had root hairs,a possible indicator of sensitivity to desiccation.Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope.Root hairs disappeared after drying,reappearing after pre-humidification,possibly an attempt to increase the surface area of the radicle for water uptake.However,the hypocotylradicle axis became darkened,probably by antioxidant system failure,causing seed death.     

Earthworm avoidance of biochar can be mitigated by wetting

Biochar has a great potential for enhancing soil fertility and carbon sequestration while enabling beneficial waste disposition. Because of the potential for widespread application, it is essential to proactively assess and mitigate any unintended consequences associated with soil biochar amendment. We conducted soil avoidance tests, growth and reproduction tests, and oxidative stress assays with the earthworm Eisenia foetida to assess the potential toxicity of soil amended with biochar produced from apple wood chips. Earthworms avoided soils containing 100 and 200 g/kg dry biochar at statistically significant levels (p < 0.05), and after 28-day incubation, these earthworms lost more weight than those in control (unamended) soil. However, biochar did not affect the reproduction of earthworms. We investigated whether the observed avoidance was due to nutrition deficiency, desiccation, or the presence of toxic polynuclear aromatic hydrocarbons (PAHs) formed during biochar production by pyrolysis. Nutrition deficiency was excluded by the lack of earthworm avoidance to soil amended with nutrient-deficient sand instead of biochar. Although traces of PAH were detected in the tested biochar (e.g., 25.9 μg/kg fluorene, 3290 μg/kg naphthalene, and 102 μg/kg phenanthrene), the lack of lipid peroxidation and no increase in superoxide dismutase activity in biochar-exposed earthworms suggests that presence of toxic compounds was not a likely reason for avoidance. Furthermore, wetting the biochar to its field capacity resulted in statistically undetectable avoidance relative to control soil, indicating that insufficient moisture could be a key factor affecting earthworm behavior in soil amended with dry biochar. To avoid desiccation of invertebrates and enable their beneficial ecosystem services, we recommend wetting biochar either before or immediately after soil application.     

板栗失水对其种子细胞透性和两种酶活性的影响

板栗栗果在室温（18～21℃）自然风干失水过程中，其种子脱氢酶（DHase）活性总趋势降低，电导率、MDA含量增加，过氧化氢酶（CAT）活性升高，到处理的第14d达最大值，然后降低。栗果含水量与其种子DHase活性之间呈显著正相关，与电导率、MDA含量呈显著负相关。当含水量从43.7%下降到30.9%，各指标变化显著，DHase活性降低122.8%，电导率增大了179.6%，MDA增加54.4%，CAT活性增大到最大值。说明，板栗优良品种铁粒头在贮藏期的含水量应保持在43%左右为好。     

The influence of desiccation and rehydration on the survival of polyembryonic seed of Citrus suhuiensis cv. limau madu

A study was carried out to investigate the influence of desiccation and freezing followed by various presowing rehydration procedures on the desiccation sensitivity of the seed of Citrus suhuiensis cv. limau madu. The freshly harvested seeds of limau madu were desiccated under a broad range of relative humidity (RH) to various equilibrium water contents (g H₂O g⁻¹ dw). The desiccated and desiccated–frozen seeds were either directly sown under germination conditions or subjected to presowing rehydration procedures: seed preheating, prehumidification and osmoconditioning. The hydrated and desiccated seeds were sown in controlled germination conditions and the survival was evaluated 4–6 weeks after sowing. The results showed that desiccation progressively reduced the percentage of normal seedling of the seeds of limau madu and the viability is almost lost at water contents below 0.08 g H₂O g⁻¹ dw. The estimated desiccation sensitivity was substantially high (WC₅₀ = 0.143 g H₂O g⁻¹ dw) when the desiccated seeds were rapidly rehydrated (uncontrolled rehydration). In contrast, seed prehumidification, preheating and osmoconditioning (controlled rehydration procedures) markedly enhanced normal seedling percentages decreasing the estimated values of WC₅₀ (between 0.08 and 0.127 g H₂O g⁻¹ dw). While the rapidly rehydrated desiccated–frozen seeds were almost killed at water content of 0.15 g H₂O g⁻¹ dw, prehumidification and preheating have noticeably increased percentage of frozen seeds survival at the same water content. However, at water content of 0.21 g H₂O g⁻¹ dw preheating significantly (P < 0.05) increased percentage of normal seedling of the frozen seeds. Seed desiccation markedly reduced the percentages of germinated seeds with multiple seedlings. Seed controlled rehydration remarkably increased the survival of polyembryos. The beneficial effect of seed controlled rehydration on the survival of the desiccated seeds was pronounced at medium water contents (0.08–0.25 g H₂O g⁻¹ dw).     

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.     

火炬松体细胞胚胎发生和干化体细胞的氧化物酶活性(英文)

培养于附加2,4-D、BA和KT的愈伤组织诱导培养基上的火炬松成熟合子胚在培养3-9周后形成白色、半透明、有光泽的粘性愈伤组织。这类愈伤组织形成于成熟合子胚的子叶,但当用NAA或者IBA代替愈伤组织诱导培养基中的2,4-D时,它的诱导频率明显降低。这种粘性愈伤组织在分化培养基上形成体细胞胚。体细胞胚经过去50μm ABA和8.5%PEG600处理后成为耐干化胚。扫描电镜观察表明,萌发处理36小时后,耐干化胚恢复到干化处理之前的状态且大小和形态正常,而不耐干化胚不能恢复到干化处理之前的状态且表面撕裂。过氧化物酶活性的分析结果表明,耐干化胚有更高的过氧化物酶活性。耐干化胚的高过氧化物酶活性可能与催化H2O2的分解和保护体细胞胚免受氧化的伤害有关。     

Improvement of Direct Somatic Embryogenesis in Rice by Selecting the Optimal Developmental Stage of Explant and Applying Desiccation Treatment

Summary

By selecting the optimal developmental stage of zygotic embryos used as expiants and applying desiccation treatment, we improved direct somatic embryogenesis in rice scutellum from two cultivars, Nipponbare and Sasanishiki. Zygotic embryos isolated 14-17, 21, 28-30 and 35-40 d after anthesis (DAA) from Nipponbare and 14-17, 18-21, 28-30 and 40-42 DAA from Sasanishiki were cultured on the embryo induction medium (EIM). Then they were transferred to embryo maturation medium (EMM) and germinated on the embryo germination medium (EGM). Only immature zygotic embryo isolated 14-17 DAA from Nipponbare and Sasanishiki could develop somatic embryos that germinated. Explants from embryos at other developmental stages could develop somatic embryos only until the elongating or scutellar stage. They enlarged and formed callus without further development. The EIM and EMM consisted of N6 macronutrients, B5 micronutrients, and B5 vitamins, supplemented with 0.1 g L^-1 casein hydrolysate, 1.5 g L^-1 proline and 1 g L^-1 MES buffer. EGM consisted of MS macro- and micronutrients and MS vitamins without organic supplement. In addition, 2 mg L^-1 2,4-D was added to EIM, 1 mg L^-1 2,4-D to EMM and 0.01 mg L^-1 zeatin to EGM. Developmental processes of somatic embryos derived from the expiants were observed by scanning electron microscopy. Desiccation treatment of maturing somatic embryo was proved to produce fully mature somatic embryos capable of germinating vigorously.     

不同脱水方法对板栗胚轴脱水敏感性和生理生化的影响

 以成熟板栗离体胚轴为材料, 通过3种脱水方法, 研究了脱水速率对板栗胚轴脱水敏感性及其相关生理的影响。研究结果表明: 硅胶脱水(快速脱水) 的胚轴脱水敏感性最低, 关键含水量最低, 胚轴的发芽率与电导率显著负相关, 胚轴的生活力与MDA含量显著负相关, 对脱水胁迫反应的忍耐力加大,同时抗氧化系统迅速启动。     

种子脱水耐性与保护系统的相关性

 综述了种子脱水耐性的研究现状, 探讨了种子脱水耐性与保护系统(蛋白质、糖、抗氧化系统和ABA等) 之间的相关性, 阐述种子脱水耐性的生理机理和分子机制, 并指出在种子脱水耐性研究方面存在的不足和今后应进一步关注的问题。