Colour at harvest and post-harvest behaviour influence paprika and chilli spice quality.

Capsicum annuum L. paprika and cayenne chilli pepper fruit were grown for red spice production and harvested at various colour stages on the same day. Fruit of each stage were allowed to change colour at room temperature with or without the addition of 100 μl l⁻¹ ethylene. Fruit appearance and colour development, and respiration and ethylene production were measured during the colouring period. Ethylene treatment had no effect on colour development or pungency for both cultivars, even though it easily crossed the cuticle, epidermis and flesh tissues into the fruit cavity. Green or deep green harvested fruit failed to fully colour red, while fruit that were harvested at or after the colour break stage visually completed their red colour development within 7–9 days. However, the colour intensity of spice powder was low for all fruit that had not developed a deep red colour prior to harvest. For paprika no difference between deep red fruit that were succulent or that had partially dried on the plant was found, but chilli fruit that had partially dried before harvest produced the most intense colour. American Spice Trade Association (ASTA) extractable red colour was the best measure of spice colour quality, compared to reflected lightness (L*), chroma (C*) and hue angle (h°) colour measurements. Pungency did not change between ripeness stages for chilli and was absent in paprika. Paprika and chilli fruit showed climacteric behaviour as long as they were attached to the plant, but when detached were non-climacteric.     

海洋酸化对栉孔扇贝钙化、呼吸以及能量代谢的影响

通过Alkalinity anomaly technique测定了栉孔扇贝Chlamys farreri在不同酸度条件下的钙化率和呼吸率,发现栉孔扇贝的钙化和呼吸活动受酸化影响显著,均随着酸化的加剧出现了明显下降。当pH降低到7.9时,栉孔扇贝的钙化率将会下降33%左右;当pH降到7.3左右时,栉孔扇贝的钙化率将趋近于0,栉孔扇贝无法产生贝壳,而此时栉孔扇贝碳呼吸率(RC)与耗氧率(RO)也分别下降了14%和11%。随着酸化的加剧,栉孔扇贝的能量代谢方式也会发生改变。这些变化都可能影响到栉孔扇贝的生存。     

利用在室温下的测定数据计算冷藏果实呼吸速率的方法探讨

利用红外线CO2分析仪测定冷藏苹果和油桃在室温(17℃或25℃)条件下的CO2变化,然后计算其在室温条件下的呼吸速率.结果表明:其呼吸速率随时间变化,在前30 min内可用直线回归方程模拟.冷藏苹果和油桃在室温条件下测出的呼吸速率不能代表其在0℃下的实际呼吸速率,但冷藏苹果和油桃的实际呼吸速率可利用在室温下的测定数据通过回归方程计算求得.     

电导法研究盐类对黄瓜冻害的预防作用

选用5种无机盐常温浸泡黄瓜,以电导法测定黄瓜冻害伤害率,研究了盐的种类、盐液pH值、盐浓度、浸泡时间等因素对黄瓜冻害的影响.试验结果表明,所选5种盐KNO3,MgSO4,NaCl,CaCl2和MgCl2中,经MgCl2浸泡后黄瓜耐冻害能力最强,最佳浸泡工艺为:MgCl2浸泡浓度为0.03 g/100 mL,pH值8.0,浸泡时间20 rain.在-18℃冷冻100 min后.空白组伤害率为57.8%,经MgCl2浸泡组为30.7%,伤害率降低了27.1%,抗冻害能力提高了46.8%.经浸泡后黄瓜呼吸强度明显降低,浸泡20min后黄瓜的呼吸强度由对照的33.8mg·(kg·h)-1降低到15.8mg·(kg·h)-1,显示盐类提高黄瓜抗冻害能力与降低其呼吸强度之间有一定关联.     

气调包装下双孢蘑菇呼吸特性

研究了双孢蘑菇在2℃和20℃下,不同薄膜包装中O_2、CO_2体积分数在蘑菇呼吸作用及薄膜渗透作用下的动态变化,结果表明低温和气调条件能有效抑制其呼吸作用。采用Michaelis-Menten型酶动力学方程,建立了2种温度下双孢蘑菇呼吸速率随O_2、CO_2体积分数变化的数学模型,同时考察了不同包装薄膜厚度对呼吸模型参数的影响,为气调包装参数的选择提供了理论基础。     

重金属污染对水稻土微生物及酶活性影响研究进展

水稻土受到重金属污染不仅影响水稻的产量品质，而且对水稻土微生物及酶活性的影响不容忽视。本文系统综述了水稻土重金属污染的来源，重金属污染对水稻土微生物生物量、种群数量、群落结构以及土壤酶活性的影响，并针对重金属污染对水稻土微生态效应研究的不足提出了未来应该研究的重点和方向，指出：①加强水稻-重金属-微生物三者相互作用、相互影响方面的研究；②在研究重金属污染与水稻土土壤微生物生态特征的关系的基础上，加强对重金属、土壤理化性状和水稻等因素进行综合并定量化分析，将是明确重金属对土壤微生物生态特性的影响及相关机理的关键；③应用分子生物学方法以及系统生物学方法，促进重金属污染胁迫下水稻土微生物活性及功能的演变规律及响应适应过程；④加强基于长期定位实验的研究，在较长的时间尺度和较大的空间尺度上认识水稻土生态系统在重金属胁迫下的演变规律和机制；⑤重金属污染对水稻土酶活性的研究应重点从机理方面入手，注重结合土壤酶的动力学参数和热力学参数，深化土壤酶与复合污染的作用机理，进一步揭示复合污染致毒途径及其机理，同时借助分子手段，探索重金属污染水稻土中更多未发现的酶的特性，寻找更加敏感、更能普遍推广的重金属污染土壤的综合性指标，以期为重金属污染水稻土的风险评价和生物修复提供科学依据。     

Functions of Nitrogen,Phosphorus and Potassium in Energy Status and Their Influences on Rice Growth and Development

Nitrogen (N), phosphorus (P) and potassium (K) are important essential nutrients for plant growth and development, but their functions in energy status remains unclear. Here, we grew Nipponbare rice seedlings in a growth chamber for 20 d at 30 °C/24 °C (day/night) under natural sunlight conditions with different nutrient regimes. The results showed that N had the strongest influence on the plant growth and development, followed by P and K. The highest nonstructural carbohydrate content, dry matter weight, net photosynthetic rate (Pn), ATP content, as well as NADH dehydrogenase, cytochrome oxidase and ATPase activities were found in the plants that received sufficient N, P and K. The lowest values of these parameters were detected in the N-deficient plants. Higher dry matter accumulation was observed in the K-deficient than in the P-deficient treatments, but there was no significant difference in the ratio of respiration rate to Pn between these two treatments, suggesting that differences in energy production efficiency may have accounted for this result. This hypothesis was confirmed by higher ATP contents and activities of NADH dehydrogenase, cytochrome oxidase and ATPase in the K-deficient plants than in the P-deficient plants. We therefore inferred different abilities in energy production efficiency among N, P and K in rice seedlings, which determined rice plant growth and development.     

Effects of chlorine dioxide treatment on respiration rate and ethylene synthesis of postharvest tomato fruit

Tomato fruit at the mature green stage were treated with ClO₂ gas in a sealed container for 12 h, and then stored at 23 °C with 85% relative humidity (RH) for 23 d. Respiration rate, respiration-related enzymes including phosphohexose isomerase (PHI), succinate dehydrogenase (SDH), and glucose-6-phosphate dehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), ethylene production, and the expression of LeAOX1a, LeCOX1, LeACS2, LeACS4 and LeACO1 genes were measured. The results showed that application of ClO₂ gas was effective in reducing total respiration, cytochrome pathway respiration and the expression of LeCOX1, but no significant reduction in the activities of respiration-related enzymes was observed during storage. Fruit treated with ClO₂ resulted in lower ethylene production. Furthermore, the expression of ethylene biosynthesis related genes, including LeACS2, LeACS4 and LeACO1 was reduced by the ClO₂ treatment. These results indicate that ClO₂ treatment might delay the ripening of tomato fruit, possibly by a mechanism involving suppression of respiration rate and ethylene biosynthesis.     

Hot water and ethanol treatments can effectively inhibit the discoloration of fresh-cut sunchoke (Helianthus tuberosus L.) tubers

The main problem affecting the quality of fresh-cut sunchoke tubers is cut surface discoloration. Pre- and post-cutting hot water and ethanol treatments were evaluated for their potential to inhibit discoloration, color changes, and associated phenolic metabolism in tuber slices stored in air at 5 °C. Some of the treatments tested inhibited discoloration and changes in a* and hue color values. Slices that were post-cut treated with hot water at 50 °C for 6–8 min or 55 °C for 3–4 min and pre-cut treated with water at 50 °C for 20–25 min maintained good color for 8–12 days at 5 °C. Post-cut ethanol fumigation (150–750 μL/L for 5 h at 5 °C) can prevent discoloration for 30 d at 5 °C. Post-cut dips with ethanol solutions (3, 5, 8 or 10% for 5 min) increased shelf-life twofold or longer compared to untreated slices. Ethanol fumigation retarded the onset of wound-induced respiration rates as well as reducing maximum rates. A post-cut 10% ethanol dip also reduced respiration rates and reduced PAL activity and total phenolics. Ethanol dips had no effect and hot water treatments had no persistent effect on microbial loads over 12 d.     

The mechanism of differential susceptibility to alternaria black spot,caused by Alternaria alternata,of stem- and bottom-end tissues of persimmon fruit

In Israel, alternaria black spot (ABS), caused by Alternaria alternata, is the main postharvest factor that reduces quality and impairs storability of persimmon fruit Diospyros kaki cv. Triumph. The fungus infects the fruit in the orchard and remains quiescent until harvest, or starts development just before harvest, following rain or high humidity. During 2–3 months of storage at 0 °C, the pathogen colonizes the fruit, eliciting ABS symptoms. Susceptibility of the fruit to A. alternata attack is characterized by colonization in the upper, stem-end tissue, in contrast to lack of development at the bottom end. Comparison between the physiology of the stem-end and the bottom-end tissues showed greater production of ethylene and CO₂ in the former during early stages of fruit growth, and greater cracked areas and reduced chlorophyll levels in the later stages of growth, before harvest. Increasing fruit weight by increasing irrigation in the orchard enhanced the cracked area and susceptibility to ABS during growth and at harvest. Wound inoculation enhanced ABS colonization in both ends of the fruit, but more significantly in the upper stem end. The present results suggest that the differential susceptibility to ABS during storage is caused by a differential ripening process, and possibly, by increased maturity at the stem end, leading to cracking and increased ABS development.