热带亚热带玉米自交系与温带玉米杂种优势的分析

选用gc1086、gc1087和gc1088 3个热带亚热带群体与1085、1095、1096、1097、1101和1102共6个中国温带骨干自交系进行不完全双列杂交试验,并对8个主要农艺性状的SCA进行了分析.结果表明:植株性状特殊配合力总体表现优良的组合为1781、1778、1779、1768、1766.产量性状表现较好的组合有1794、1792、1787和1777.来自母本gc1087的组合可以选育出高产玉米品系;来自母本gc1088的组合可以选育出饲料玉米品系.     

The biogeochemical cycles of trace metals in the oceans

Planktonic uptake of some essential metals results in extraordinarily low concentrations in surface seawater. To sequester or take up these micronutrients, various microorganisms apparently release strong complexing agents and catalyze redox reactions that modify the bioavailability of trace metals and promote their rapid cycling in the upper water column. In turn, the low availability of some metals controls the rate of photosynthesis in parts of the oceans and the transformation and uptake of major nutrients such as nitrogen. The extremely low concentrations of several essential metals are both the cause and the result of ultraefficient uptake systems in the plankton and of widespread replacement of metals by one another for various biochemical functions.     

热带生态区不同施氮水平对超级杂交稻产量及生长发育的影响

在海南三亚热带生态条件下,以超级杂交水稻组合两优培九和苗头组合两优0293、GD—1S／RB207为材料,设置5个不同施氮水平,即分别施纯氮0（N1,CK）、150（N2）、300（N3）、450（N4）、600（N5）kg／hm2,研究不同施氮水平对水稻产量及生长发育的影响．结果表明,两优培九和GD-1S／RB207在N3处理下的产量最高,两优0293在N4处理下的产量最高,但与N3处理下的产量相近．初步认为,在海南三亚生态条件下,超级杂交水稻的适宜总施氮水平为纯氮300kg／hm2,且氮肥（纯氮）用量每增加150kg／hm2,始穗期和齐穗期均相应推迟3-6d,最后全生育期延长3～6d．随着施氮水平的提高,伤流量增加,施氮量大于450kg／hm2后,随着施氮水平的进一步提高,伤流量不增反降．施纯氮0～450kg／hm2,随着施氮水平的提高,表层根所占体积比下降,中层根所占体积比上升,施纯氮450～600kg／hm2,随着施氮水平的提高,表层根所占体积比上升,中层根所占体积比下降．超级杂交稻两优培九和两优0293的剑叶张角随着施氮量的增加,表现出先增大后减小再增大的变化趋势;其剑叶表现出变长、变宽的趋势．     

Global patterns of predator diversity in the open oceans

The open oceans comprise most of the biosphere, yet patterns and trends of species diversity there are enigmatic. Here, we derive worldwide patterns of tuna and billfish diversity over the past 50 years, revealing distinct subtropical "hotspots" that appeared to hold generally for other predators and zooplankton. Diversity was positively correlated with thermal fronts and dissolved oxygen and a nonlinear function of temperature (approximately 25 degrees C optimum). Diversity declined between 10 and 50% in all oceans, a trend that coincided with increased fishing pressure, superimposed on strong El Ni?o-Southern Oscillation-driven variability across the Pacific. We conclude that predator diversity shows a predictable yet eroding pattern signaling ecosystem-wide changes linked to climate and fishing.     

High frequency of horizontal gene transfer in the oceans

Oceanic bacteria perform many environmental functions, including biogeochemical cycling of many elements, metabolizing of greenhouse gases, functioning in oceanic food webs (microbial loop), and producing valuable natural products and viruses. We demonstrate that the widespread capability of marine bacteria to participate in horizontal gene transfer (HGT) in coastal and oceanic environments may be the result of gene transfer agents (GTAs), viral-like particles produced by α-Proteobacteria. We documented GTA-mediated gene transfer frequencies a thousand to a hundred million times higher than prior estimates of HGT in the oceans, with as high as 47% of the culturable natural microbial community confirmed as gene recipients. These findings suggest a plausible mechanism by which marine bacteria acquire novel traits, thus ensuring resilience in the face of environmental change.     

Suspended particulate matter: concentration in the major oceans

Quantitative data from over 500 concentrates of suspended particulate material has been summarized statistically for the Atlantic, Pacific, and Indian oceans, the Gulf of Mexico, and the Caribbean Sea. From clear ocean water a majority of samples were in the range of 0 to 9.9 milligrams per 200 liters and the next largest number were in the range of 10 to 19.9 milligrams per 200 liters. Certain areas of cloudy or nepheloid water, observed photographically, contain relatively more samples in heavier concentration ranges and have larger mean values than clear ocean water.     

Detection of anthropogenic climate change in the world's oceans

Large-scale increases in the heat content of the world's oceans have been observed to occur over the last 45 years. The horizontal and temporal character of these changes has been closely replicated by the state-of-the-art Parallel Climate Model (PCM) forced by observed and estimated anthropogenic gases. Application of optimal detection methodology shows that the model-produced signals are indistinguishable from the observations at the 0.05 confidence level. Further, the chances of either the anthropogenic or observed signals being produced by the PCM as a result of natural, internal forcing alone are less than 5%. This suggests that the observed ocean heat-content changes are consistent with those expected from anthropogenic forcing, which broadens the basis for claims that an anthropogenic signal has been detected in the global climate system. Additionally, the requirement that modeled ocean heat uptakes match observations puts a strong, new constraint on anthropogenically forced climate models. It is unknown if the current generation of climate models, other than the PCM, meet this constraint.     

Penetration of human-induced warming into the world's oceans

A warming signal has penetrated into the world's oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences. Changes in advection combine with surface forcing to give the overall warming pattern. The implications of this study suggest that society needs to seriously consider model predictions of future climate change.     

Decomposition of calcium carbonate and organic carbon in the deep oceans

Simple mass-balance calculations indicate that in seawater the calcium variation (DeltaCa) correlates with the variation in the titration alkalinity (DeltaTA) and the variation in the total carbon dioxide (DeltasigmaCO(2)) or nitrate (DeltaNO(3)) according to the equations DeltaCa = 0.46288 DeltaTA + 0.074236 DeltasigmaCO(2) and DeltaCa = 0.5 DeltaTA + 0.53125 DeltaNO(3). The estimated values for DeltaCa from these equations, which agree with the values obtained from direct measurements, have been used to estimate the ratio of the in situ inorganic to organic carbon fluxes in the oceans. The precise vertical distribution of this ratio is shown for the first time.