施肥对落叶松和水曲柳人工林土壤微生物生物量碳和氮季节变化的影响

2007-2008年,采用氯仿熏蒸浸提法测定了落叶松和水曲柳人工林土壤微生物生物量,研究施N肥对土壤微生物生物量碳、氮,以及细菌、真菌和放线菌数量季节变化的影响.结果表明：落叶松林地土壤微生物生物量碳、氮两年平均值分别比水曲柳林地低13.8%和18.3%,但两种林分土壤微生物生物量碳、氮具有相同的季节变化规律：5月最低,9月最高;表层（0～10 cm）土壤微生物生物量碳、氮及微生物数量均高于亚表层（10～20 cm）土壤.但细菌、真菌和放线菌数量的季节变化格局与生物量不同.施肥降低了两种林分的微生物生物量碳、氮,以及细菌、真菌和放线菌数量,其中,落叶松林地微生物生物量碳和氮分别降低了24%和63%,水曲柳分别降低了51%和68%.说明施N肥限制了土壤微生物生物量,改变了土壤微生物的群落结构.     

长江口海域真刺唇角水蚤的分布及其对全球变暖的响应

基于1959和2002年在长江口28°00′—32°00′N、122°00′—123°30′ E海域4个季节8个航次的海洋调查资料,分析了长江口海域真刺唇角水蚤的水平分布和季节变化特征及其对气候变暖的响应.结果表明：长江口海域真刺唇角水蚤平均丰度在夏秋季较低、冬春季较高,冬季真刺唇角水蚤的出现率最高,春、夏季具明显的集群性;盐度是影响真刺唇角水蚤水平分布的主要因素,该种分布的最适温度约16 ℃,最适盐度在12～20,属暖温性咸淡水种;与1959年相比,2002年长江口海域真刺唇角水蚤丰度明显降低,这可能与全球变暖有关,可作为长江口海洋变暖的一个重要指示种.春季真刺唇角水蚤的高丰度值出现在长江口最大浑浊带水域,这对于维持该水域渔场功能和生态系统的其他功能具有重要意义.     

长期定位施肥下黑土碳排放特征及其碳库组分与酶活性变化

黑土作为承担我国粮食安全与生态安全的重要土壤资源,其碳排放特征与碳库组分变化一直是生态学领域研究的热点。施肥是影响黑土有机碳输入、输出的重要因素,而这需要长时间尺度的探究。为明确长期不同施肥下的土壤碳排放特征及其影响机制,以始于1990年的国家土壤肥力与肥料效益监测网站黑土监测基地-公主岭为研究平台,选取不施肥(CK)、单施氮磷钾肥(NPK)、无机肥配施低量有机肥(NPKM1)、1.5倍的无机肥配施低量有机肥(1.5(NPKM1))、无机肥配施高量有机肥(NPKM2)和无机肥配施秸秆(NPKS)6个处理,探讨了长期不同施肥下土壤碳排放量(CO2-C)与土壤碳库组分包括水溶性有机碳(DOC)、微生物量碳(MBC)、颗粒有机碳(POC)、易氧化有机碳(ROC)及其β-葡萄糖苷酶(BG)、木聚糖酶(BXYL)、纤维素酶(CBH)和乙酰基β-葡萄糖胺酶(NAG)等酶活性变化。结果表明:与CK相比,各施肥处理均可以显著增加黑土土壤碳排放量(P0.05),其中,NPK处理土壤碳排放量约为2633.33 kg/hm~2,显著高出CK处理37.36%;长期有机无机配施(NPKM1、1.5(NPKM1)、NPKM2)显著增加土壤碳排放量71.81%—88.51%,效果最为明显;NPKS显著增加土壤碳排放量56.32%,并且三种长期有机无机配施措施碳排放差异不显著。相对CK处理,有机无机配施的DOC、MBC、POC、ROC均有显著增加(P0.05),各指标分别高出CK处理16.07%—56.34%、128.84%—185.77%、284.15%—497.45%和841.03%—1145.94%,其中1.5(NPKM1)处理效果最好。同时,有机无机配施相对CK处理的NAG、BG、BXYL和CBH活性分别提高了313.22%—452.65%、129.45%—250.74%、159.08%—273.32%和72.21%—193.53%,且以1.5(NPKM1)处理的效果最好。土壤碳排放量与土壤酶活性、土壤活性碳库组分之间的相关性分析结果表明,长期不同施肥措施的土壤碳排放量不但与土壤ROC、DOC、POC、MBC含量呈极显著相关(P0.001),也与土壤BG、NAG、CBH、BXYL酶活性呈极显著相关(P0.001),说明施肥可以通过改变土壤各活性碳库组分含量与土壤微生物活性影响土壤碳排放量。     

日光温室冬季增施CO2对切花红掌光合作用及生长发育的影响

针对切花红掌日光温室冬季生产时CO₂亏缺严重的现象,以不增施CO₂为对照,研究了增施700、1000、1300 μmol·mol^-1浓度CO₂对切花红掌‘火焰’光合特性和生长发育的影响.结果表明: 增施60 d CO₂,红掌叶片的净光合速率、胞间CO₂浓度和水分利用效率均显著提高,且以1000 μmol·mol^-1处理的增幅最大;而气孔导度则较对照显著下降.增施CO₂后,红掌叶片的可溶性糖、淀粉和可溶性蛋白含量均较对照显著增加,佛焰苞大小、色泽、花茎长度等切花品质参数,以及叶片发育质量参数和花茎生长速率均有不同程度的提高,且均以1000 μmol·mol^-1浓度最佳.增施1000 μmol·mol^-1的CO₂可以有效促进日光温室切花红掌的冬季生产.     

长期不同施肥方式对黄潮土肥力特征的影响

依托黄潮土35 年长期定位试验,以2种土壤物理肥力指标、8种土壤化学肥力指标和5种土壤生物肥力指标进行主成分分析,最后将各主成分得分系统进行聚类分析.结果表明: 不同施肥方式对土壤肥力指标影响显著.施用有机肥处理(M、MN、MNP、MNPK)与NPK处理相比,土壤容重显著降低,而土壤孔隙度、有机质、全氮、碱解氮、全磷、有效磷、微生物生物量和过氧化氢酶、脲酶、碱性磷酸酶活性均显著增加;通过主成分分析可将原15个土壤指标降维,提取出2个主成分,反映了原信息量的85.5%,且无原变量丢失.土壤容重、孔隙度、有机质、全氮、碱解氮、全磷、有效磷、速效钾、微生物生物量、过氧化氢酶、脲酶、碱性磷酸酶、蔗糖酶活性在第1主成分上有较高因子负荷,全钾和pH在第2主成分上有较高因子负荷;以2个主成分得分为新指标进行聚类,得到长期不同施肥方式对黄潮土的培肥效果排序为MNPK＞MNP＞M、MN＞NPK＞N、NP＞CK.可见施用有机肥对黄潮土培肥效果更显著,以有机肥配施氮磷钾化肥方式效果最优.     

Autocrine embryotropins revisited: how do embryos communicate with each other in vitro when cultured in groups?

In the absence of the maternal genital tract, preimplantation embryos can develop in vitro in culture medium where all communication with the oviduct or uterus is absent. In several mammalian species, it has been observed that embryos cultured in groups thrive better than those cultured singly. Here we argue that group‐cultured embryos are able to promote their own development in vitro by the production of autocrine embryotropins that putatively serve as a communication tool. The concept of effective communication implies an origin, a signalling agent, and finally a recipient that is able to decode the message. We illustrate this concept by demonstrating that preimplantation embryos are able to secrete autocrine factors in several ways, including active secretion, passive outflow, or as messengers bound to a molecular vehicle or transported within extracellular vesicles. Likewise, we broaden the traditional view that inter‐embryo communication is dictated mainly by growth factors, by discussing a wide range of other biochemical messengers including proteins, lipids, neurotransmitters, saccharides, and microRNAs, all of which can be exchanged among embryos cultured in a group. Finally, we describe how different classes of messenger molecules are decoded by the embryo and influence embryo development by triggering different pathways. When autocrine embryotropins such as insulin‐like growth factor‐I (IGF‐I) or platelet activating factor (PAF) bind to their appropriate receptor, the phosphatidylinositol‐4,5‐bisphosphate 3‐kinase (PI3K) pathway will be activated which is important for embryo survival. On the other hand, the mitogen‐activated protein kinase (MAPK) pathway is activated when compounds such as hyaluronic acid and serotonin bind to their respective receptors, thereby acting as growth factors. By activating the peroxisome‐proliferator‐activated receptor family (PPAR) pathway, lipophilic autocrine factors such as prostaglandins or fatty acids have both survival and anti‐apoptotic functions. In conclusion, considering different types of messenger molecules simultaneously will be crucial to understanding more comprehensively how embryos communicate with each other in group‐culture systems. This approach will assist in the development of novel media for single‐embryo culture.     

Autophagy is required for gamete differentiation in the moss Physcomitrella patens

Autophagy, a major catabolic process in eukaryotes, was initially related to cell tolerance to nutrient depletion. In plants autophagy has also been widely related to tolerance to biotic and abiotic stresses (through the induction or repression of programmed cell death, PCD) as well as to promotion of developmentally regulated PCD, starch degradation or caloric restriction important for life span. Much less is known regarding its role in plant cell differentiation. Here we show that macroautophagy, the autophagy pathway driven by engulfment of cytoplasmic components by autophagosomes and its subsequent degradation in vacuoles, is highly active during germ cell differentiation in the early diverging land plant Physcomitrella patens. Our data provide evidence that suppression of ATG5-mediated autophagy results in reduced density of the egg cell-mediated mucilage that surrounds the mature egg, pointing toward a potential role of autophagy in extracellular mucilage formation. In addition, we found that ATG5- and ATG7-mediated autophagy is essential for the differentiation and cytoplasmic reduction of the flagellated motile sperm and hence for sperm fertility. The similarities between the need of macroautophagy for sperm differentiation in moss and mouse are striking, strongly pointing toward an ancestral function of autophagy not only as a protector against nutrient stress, but also in gamete differentiation.     

大棚辣椒最佳钾肥用量及运筹

以台湾‘长香’辣椒Capsicum frutescens品种为材料,通过设置钾肥横向与纵向施肥的田间试验,探讨辣椒最佳钾肥用量及其运筹。结果表明,在设定氮、磷肥施用量分别为15.0、3.5 kg·667m-2的条件下,钾肥不同施用量对辣椒的株高、幅宽、茎粗的长势及果长、果粗、单果重等品质均有明显的影响,辣椒产量(y)与钾肥施用量(x)两者呈y = -2.2743x2 + 53.402x + 802.45的相关性(r2 = 0.973),钾肥最佳施用量为11.74 kg·667m-2;在同样条件下,钾肥施用量12.00 kg·667m-2,按基肥与追肥不同比例进行施用,辣椒株高、幅宽、茎粗的长势及果长、果粗、单果重等品质与产量均有所差异,其基肥∶追肥按2∶8的配比进行运筹施用,辣椒品质与产量均明显优于其他配比。