套作棉根际与非根际土壤酶活性和养分的变化

在棉麦两熟双高产条件下研究了棉花根际与非根际土壤酶活性和养分含量的变化.结果表明,套作棉土壤脲酶、蔗糖酶、蛋白酶及过氧化氢酶活性随生育进程的变化趋势与单作棉表现一致,但整个生育期套作棉根际与非根际土壤各种酶活性均明显高于单作棉.套作棉根际与非根际土壤养分含量在麦棉共生期低于单作棉或差异较小,而在麦收后则显著高于单作棉.套作棉土壤养分含量随生育进程的变化趋势与单作棉大体相同,但一些养分的吸收高峰晚于单作棉.无论套作棉还是单作棉,根际土壤酶活性和养分含量高于非根际.土壤各养分含量与土壤脲酶、蔗糖酶和蛋白酶活性呈显著(P=0.0,n=32)或极显著(P=0.01,n=32)相关,与土壤过氧化氢酶活性相关不显著.     

根结线虫对黄瓜叶片氮磷含量、土壤pH和酶活性的影响

通过盆栽试验,采用人工接种的方法研究了接种根结线虫对黄瓜植株根际和非根际土壤pH值、土壤酶活性及叶片N、P含量的影响.结果表明:根际土壤pH值在接种量达到每株6000个时才显著降低;随着接种量的增加,叶片N、P含量、根际土壤过氧化物酶、根际和非根际土壤多酚氧化酶活性逐渐降低,根际土壤过氧化氢酶活性却逐渐升高,非根际土壤pH值先升高后降低,非根际土壤过氧化氢酶活性没有明显的变化规律.接种根结线虫后,根际土壤脲酶活性显著降低,根际和非根际土壤磷酸酶活性、非根际土壤过氧化物酶活性仅在较高接种量时才显著降低.根际土壤pH值、酶活性及叶片N、P含量之间多数呈极显著相关,而非根际土壤pH值、酶活性及叶片N、P含量之间只有部分呈极显著相关.     

施氮量对夏玉米根际和非根际土壤酶活性及氮含量的影响

在华北平原潮土上进行田间试验,研究施氮量对夏玉米根际和非根际土壤酶活性及氮含量的影响.结果表明: 不同施氮水平下土壤酶活性均表现出一致的季节性变化趋势.与不施氮处理相比,施氮处理能显著提高根际和非根际土壤硝态氮含量及根际土壤铵态氮含量,显著增强土壤几丁质酶、β-葡萄糖苷酶、纤维素酶和木聚糖酶活性.在整个玉米生育期内,非根际土壤硝态氮含量显著高于根际土壤;非根际土壤铵态氮含量在灌浆期显著高于根际土壤,但在苗期和完熟期则显著低于根际土壤;根际土壤几丁质酶、β-葡萄糖苷酶、纤维素酶和木聚糖酶活性都显著高于非根际土壤.施氮对土壤有机质含量没有显著影响;在0～180 kg·hm^-2施氮范围内,施氮可明显增加土壤全氮含量,但当施氮量超过180 kg·hm^-2时,土壤全氮含量则明显下降.综上,适量施氮能显著增强土壤酶活性,提高土壤全氮含量,改善土壤生化性质.     

入侵植物薇甘菊的根际土壤微生物特征

盆栽试验比较入侵植物薇甘菊(Mikania micrantha)和本土植物爬山虎(Parthenocissus tricuspidata)生长过程中的根际土壤微生物结构(磷脂脂肪酸方法)、酶活性及理化性质的特征, 以期揭示薇甘菊入侵过程中的土壤微生物学机制。结果显示: 与本地种爬山虎相比, 薇甘菊根际土壤pH 值降低, 有机质、总氮、铵氮和有效磷含量减少, 但硝态氮含量增加。薇甘菊根际土壤的细菌、真菌、放线菌脂肪酸含量高于爬山虎, 脱氢酶、脲酶、蛋白酶和磷酸酶活性显著增强。相关分析表明土壤微生物磷脂脂肪酸含量及酶活性与土壤有机质、氮、磷营养盐呈显著相关。     

嫁接茄的黄萎病抗性与根际土壤生物学活性的关系

以野生茄托鲁巴姆(Solanum torvum)和刺茄(S.surattense)为砧木,西安绿茄(smelongena)为接穗,研究了嫁接茄的抗黄萎病效果及其根际土壤微生物种群数量和酶活性变化,探讨了嫁接茄的抗病性与根际土壤生物学活性的关系.结果表明:嫁接茄的抗病效果明显,其根际微生物种群数量及所占比例、根际土壤酶活性均发生了改变,且不同生育时期存在一定的动态变化.总体看,嫁接茄的抗病性增强,与其根际放线菌数量增加、放线菌数量与真菌数量的比值提高,根际土壤脱氢酶、多酚氧化酶活性提高有关.     

有机物料对黄河三角洲滨海盐土根际效应的影响Ⅰ．──养分和酶生物学效应

采用根际袋法研究腐熟有机物料对滨海盐土水稻根际养分和酶活性特征的影响．结果表明,施用有机物料可增加土壤有效Ｎ、Ｐ、Ｋ、Ｆｅ和Ｚｎ的含量,增强土壤尤其根际土壤的转化酶、碱性磷酸酶和豚酶活性,可加速土壤有机Ｃ、Ｎ、Ｐ的代谢作用,增加水稻养分吸收,改善生长发育,增强耐盐性．     

有机物料对黄河三角洲滨海盐土根际效应的影响Ⅰ.养分和酶生物学…

采用根际袋法研究腐熟有机物料对滨海盐土水稻根际养分和酶活性特征的影响,结果表明,施有秀机物料可增加土壤有效Ｎ、Ｐ、Ｋ,Ｆｅ和Ｚｎ的含量增强土壤尤其根际土壤的转化酶、碱性磷酸酶和脲酶活性,可加速土壤有机Ｃ、Ｎ、Ｐ的代谢作用,增加水稻养分吸收,改善生长发育,增强耐盐性。     

异丙甲草胺对芹菜根际与非根际生物活性的影响

通过根际袋法土培试验,研究了异丙甲草胺对芹菜根际与非根际土壤酶活性、土壤微生物数量的影响以及异丙甲草胺在根际与非根际土壤中的降解特性.结果表明,异丙甲草胺对土壤过氧化氢酶活性有一定的抑制作用,对土壤脱氢酶活性有激活作用.一般情况下根际土壤酶活性均要大于非根际土壤.异丙甲草胺作用45 d后,芹菜根际土壤细菌、真菌数量大于非根际土壤,根际效应R/S在1.76～2.51之间;异丙甲草胺对土壤放线菌数量影响不大,根际效应不明显.异丙甲草胺在根际土壤与非根际土壤中的降解速率分别为0.0217和0.0176,相应的半衰期分别为31.9和39.4 d.在根际土壤中异丙甲草胺更易降解.     

高寒灌丛生长季根际和非根际土壤多酚氧化酶和过氧化氢酶活性对增温的响应

研究青藏高原东部窄叶鲜卑花高寒灌丛生长季根际和非根际土壤多酚氧化酶和过氧化氢酶活性对增温(1.3 ℃)的响应,分析全球气候变暖对高寒灌丛根际土壤生态过程的影响.结果表明:生长季中期根际和非根际土壤多酚氧化酶活性显著高于生长季初期和末期;而土壤过氧化氢酶活性在非根际土壤中随生长季节逐步提高,在根际土壤中没有表现出明显的季节变化.在非根际土壤中,增温使生长季末期土壤多酚氧化酶活性和生长季中期土壤过氧化氢酶活性显著提高17.5%和2.2%,而在其他时期对2种土壤酶活性没有显著影响.而在根际土壤中,增温仅在生长季初期使土壤多酚氧化酶和过氧化氢酶活性显著提高6.5%和1.3%.在整个生长季,土壤多酚氧化酶活性均表现为正根际效应,土壤过氧化氢酶活性的根际效应不明显,而增温仅在生长季末期使土壤多酚氧化酶活性的根际效应显著降低15.2%.这表明,未来气候变暖背景下青藏高原东部高寒灌丛生态系统根际与非根际土壤多酚氧化酶和过氧化氢酶活性将发生不同的变化,进而影响高寒灌丛根际土壤生态过程.     

玉米幼苗根际土壤微生物活性对芘污染的响应

用根际袋法土培试验研究了玉米幼苗根际与非根际土壤微生物量碳、微生物熵、代谢熵和土壤酶活性对不同芘污染水平(50、200、800mg·kg-1,记为T1、T2、T3)的响应差异。结果表明,较低浓度芘可适当的刺激玉米幼苗的生长,而较高浓度芘则抑制幼苗生长,其抑制作用随芘处理浓度的提高而增强;芘对玉米根系的影响要大于对茎叶的影响。玉米幼苗能够明显促进土壤中芘的去除。根际和非根际土壤中芘的去除率分别为56.67%-76.18%和32.64%-70.44%,根际土壤中芘的平均去除率比非根际土壤高16.06%。同处理中根际土壤芘含量显著低于非根际土壤,随着芘处理浓度的提高其差异更加显著。根际土壤微生物量碳、微生物熵、多酚氧化酶活性、脱氢酶活性和磷酸酶活性均高于非根际土壤,代谢熵低于非根际土壤,且其差异随芘处理浓度的提高而增大。在不同芘污染水平下,微生物量碳、微生物熵和脱氢酶活性根际和非根际土壤为T1T2T3,代谢熵为T3T2T1;多酚氧化酶活性根际土壤为T2T1T3,非根际土壤为T1T2T3;磷酸酶活性根际土壤为T3T1T2,非根际土壤为T1T2T3。土壤中残余芘含量与土壤微生物量碳、微生物熵、多酚氧化酶、脱氢酶和磷酸酶活性呈显著负相关,与代谢熵呈显著正相关。     

Litter and its interaction with standing vegetation affect seedling recruitment in Tibetan alpine grasslands

Background: Seedling recruitment is widely recognised to be important in the maintenance of diversity and coexistence of species. It is not clear how local abiotic factors mediated by litter and biotic interactions influence plant species recruitment in alpine grasslands.

Aims: To determine how litter and standing vegetation affected seedling recruitment in plant communities in Tibetan alpine grasslands.

Methods: Seedling recruitment was quantified in response to experimental treatments: (1) removal of standing vegetation and litter; (2) removal of standing vegetation with litter intact; (3) intact standing vegetation and removal of litter and (4) control: intact standing vegetation and litter.

Results: Litter removal increased seedling numbers, while standing vegetation removal had no effect. An interaction between litter and standing vegetation removal marginally increased seedling number. Species richness of seedlings was not related to either litter removal or standing vegetation removal. Species composition of seedling differed significantly between removal of both litter and standing vegetation and control.

Conclusions: Litter and its interaction with standing vegetation has an important role in affecting plant species recruitment in this alpine plant community. In contrast, biotic interactions, such as competition or facilitation from standing vegetation, appear to have only minor effects on recruitment.     

Potentiality of Different Seed Priming Agents to Mitigate Cold Stress of Winter Rice Seedling

Seed priming has proved to be an effective pre-germination seed invigoration technique for different crops to improve seed and seedling performance under different abiotic stresses. In Bangladesh, winter rice is very often exposed to cold waves just after sowing in the nursery bed resulting in poor seed germination and seedling emergence, yellowish and thin seedlings production, and a very low survival rate. Seed priming may mitigate the cold stress during seed germination and seedling emergence and helps in the quality seedling production of winter rice. To evaluate the efficacy of different seed priming techniques in increasing seedling emergence, growth, vigor and survivability of winter rice cultivars under cold stress, a pot experiment was conducted at the Department of Agronomy, Bangladesh Agricultural University during December 2018 to January 2019. The experiment comprised two factors, (A) Winter rice variety namely, i) BRRI dhan29 and ii) BRRI dhan36; (B) Seed priming agent namely i) Control (no priming), ii) 20000 ppm NaCl, iii) 30000 ppm NaCl, iv) 20000 ppm KCl, v) 30000 ppm KCl, vi) 20000 ppm CaCl₂, vii) 30000 ppm CaCl₂, viii) 50 ppm CuSO₄, ix) 75 ppm CuSO₄, x) 10000 ppm ZnSO₄, xi) 15000 ppm ZnSO₄, xii) 2 ppm Na₂MoO₄, xiii) 3 ppm Na₂MoO₄, xiv) 100 ppm PEG (Polyethylene glycol 4000) and xv) 150 ppm PEG. Seeds were sown on two different dates viz., 1st December and 1st January so that seedlings are exposed to cold stress at different stages. The experiment was laid out in a completely randomized design (CRD) with three replications. Results indicated that (in most of the cases) seed priming has a positive impact on seedling emergence rate (%), root length, shoot length, root shoot ratio, root dry weight, shoot dry weight, seedling dry weight and survival rate (%). Among the priming agents, KCl and CaCl₂ performed best; while priming with NaCl and PEG showed no advantages over no priming for both the sowing dates. In general, BRRI dhan36 performed better than BRRI dhan29 in terms of seedling growth because of its higher tolerance to cold stress. But, both the varieties performed similarly in terms of emergence rate and survival rate. Thus, priming is an effective tool to increase seed germination, better seedling growth, and higher seedling survivability of winter rice under cold stress, and KCl (20000 ppm) or CaCl₂ (20000 ppm) can be considered as a viable priming agent.     

Seed mass and seedling establishment after fire in Ku‐ring‐gai Chase National Park,Sydney, Australia

Abstract Relationships between seed mass and several aspects of plant regeneration ecology were investigated in a post‐fire environment in Ku‐ring‐gai Chase National Park near Sydney, Australia. We found a significant positive relationship between seed mass and time to seedling emergence (P < 0.001) and a strong negative relationship between seed mass and time between emergence and production of the first true leaf (P < 0.001). Surprisingly, we found no relationship between seed mass and seedling establishment (P = 0.21). It seems most likely that this lack of relationship is a result of the many stochastic factors affecting seedling establishment during any given recruitment episode at any given site. A cause of mortality was assigned to 56% of the 781 seedlings that died during the present study. There was no relationship between cause of death and seed mass (P = 0.28). Of the seedlings for which the cause of death was known, 57% were killed by herbivory and 21% were killed by drought. Seedling–seedling competition affected only one species.     

Does a latitudinal gradient in seedling survival favour larger seeds in the tropics?

The mean size of seeds produced by plants at the equator is two to three orders of magnitude higher than the mean size of seeds produced by plants at 60°. We compiled data from the literature to assess the possibility that this latitudinal gradient in seed size allows species to cope with more difficult seedling establishment conditions in tropical environments. We found no relationship between latitude and seedling survival through 1 week (P = 0.27, n = 112 species). There was also no evidence that a larger seed mass is required to gain a given level of seedling survival in tropical environments (P = 0.37, n = 112 species), and no relationship between latitude and the duration of the juvenile period (P = 0.57, n = 132 species). Thus, our results are not compatible with the idea that seedling establishment is more difficult in the tropics.     

不同育苗方式对移栽后侧柏和白榆幼苗根系生长的影响

不同类型苗木,具有不同的根系结构特征,其根系结构也将影响林木的生长和恢复生态系统的稳定性。以侧柏和白榆为研究对象,对移栽18个月后的种基盘苗与营养钵苗根系的生长进行了调查。结果表明:侧柏种基盘苗的总根长和平均直径比营养钵苗分别增加了316.20 cm和0.05mm,白榆苗则分别增加了651.54 cm和0.88mm。侧柏和白榆种基盘苗的根系表面积比营养钵苗分别增加了40.05%和73.04%。侧柏种基盘苗的根系总体积与营养钵苗的差异不显著,而白榆种基盘苗的根系总体积则比营养钵苗增加了54.70%。侧柏和白榆营养钵苗的一级侧根数量大于种基盘苗,增幅分别为42.31%和30.65%。对于侧柏来说,营养钵苗的根尖总数比种基盘苗的增加324个,但白榆苗差异不显著。各种处理的幼苗总根长与根系表面积都有显著相关性,但与根体积不具有显著相关性。营养钵苗的根系平均直径和根尖数量具有相对独立性,而种基盘的根系平均直径与总根长以及根体积均表现为显著相关。种基盘苗能提高侧柏、白榆幼苗的根冠比,促进幼苗株高、地径和主根的生长。采用种基盘苗进行植被恢复,由于其具有较大的根表面积和根长度,林木便具有了较大的吸收水分和营养的能力,以及较高的固结表层土壤能力。     

茄子嫁接苗与自根苗光合特性比较

对茄子嫁接苗与自根苗的光合生理特性进行了比较研究。结果表明,不同时期嫁接苗功能叶片的净光合速率（Pn）均显著高于自根苗;茄子嫁接苗与自根苗功能叶片的Pn日变化均呈“双峰”曲线,但嫁接苗的“午休”程度较自根苗轻;嫁接苗比自根苗有较低的光补偿点（LCP）和CO2补偿点（CCP）,较高的光饱和点（LSP）和CO2饱和点（CSP）;有较低的光合冷限温度和较高的光合热限温度,光合最适温度两者之间没有明显的差别;有较高的光饱和、CO2饱和及最适温度时的Pn;嫁接苗Pn高是因为嫁接苗胞间的光合反应的底物浓度大（Ci高）,表观量子效率（AQY）、羧化效率（CE）和光合能力（A350）高的缘故。     

Cotyledon venation patterns in the Leguminosae: Gaesalpinioideae

Cotyledon venation patterns are described for 93 species representing all tribes of the Caesalpinioideae. Patterns are grouped into a series of levels of complexity according to the number of primary veins, nine, seven, six, five, three or one, but five- and three-vein patterns predominate. The number of petiolar vascular strands varies from one to eight but most species have two or four strands. It is proposed that all the patterns have been derived from one in which four strands and a protoxylem trace in the petiole branch and anastomose to form seven primary veins in the lamina. Venation patterns show correlations with cotyledon anatomy, size and shape and with taxonomic grouping at tribal, infratribal and generic levels. Each tribe is characterized by a particular set of related patterns, pattern frequencies and evolutionary trends.     

四种沙埋深度对羊草种子出苗和幼苗生长的影响

模拟羊草种子自然埋藏深度状况,设计了0、1、2和3cm共4种沙埋深度实验,研究了其出苗率及幼苗生长对沙埋深度的响应。结果表明,羊草种子出苗率随埋深的增加呈下降趋势,0cm时出苗率最高为89.3%,1和2cm时分别为81.5%和78.5%,3cm时最低(73.5%),与前三者具有显著差异。埋深对地上株高生长动态的影响主要表现在,播种后25d,0～2cm处理的羊草幼苗地上株高均高于3cm处理;播种后36d,4种处理的地上株高没有显著差异。此外,随着埋深的增加,羊草幼苗的根长、根数、根冠比呈先上升后下降趋势,叶片数呈下降趋势,绝对株高则呈上升趋势。表明1～2cm沙埋深度更适宜于羊草种子出苗及幼苗生长,而0或3cm埋深不利于其出苗和幼苗生长。     

Restoration of a Restinga Sandy Coastal Plain in Brazil: Survival and Growth of Planted Woody Species

In this article we report the results of an experiment introducing 17 native shrub and tree species into a Brazilian restinga (i.e., coastal sandy plain vegetation). Restingas have been affected by human impact for about 8,000 years, and human occupation for housing, tourism, and land speculation has recently increased in such a way that there is a need for conservation of remnant patches and restoration of degraded areas throughout the coast to protect biodiversity. Our study site is a remnant located in Rio de Janeiro, the second largest city in the country, and has been subjected in the past to deforestation, man‐made fire, and sand extraction. Although trees and shrubs predominantly compose natural restinga vegetation, local vegetation after impact was replaced by an exotic grass cover, which meant a drastic reduction in species richness. Thus, in this experiment we removed the grass cover, introduced shrub and tree species, and monitored survival and growth of 20 plants per species for 2 years. Despite the adversities imposed by the nutrient‐poor sandy soil, 70% of the species showed high survival percentage and considerable growth. This report on restoration initiatives in the restingas points out the viability of shrub and tree plantation following exotic grass removal as a strategy to restore Brazilian coastal vegetation.