Arabidopsis H+-PPase AVP1 regulates auxin-mediated organ development     

Li J  Yang H  Peer WA  Richter G  Blakeslee J  Bandyopadhyay A  Titapiwantakun B  Undurraga S  Khodakovskaya M  Richards EL  Krizek B  Murphy AS  Gilroy S  Gaxiola R 《Science (New York, N.Y.)》2005,310(5745):121-125

The transport of auxin controls developmental events in plants. Here, we report that in addition to maintaining vacuolar pH, the H+-pyrophosphatase, AVP1, controls auxin transport and consequently auxin-dependent development. AVP1 overexpression results in increased cell division at the onset of organ formation, hyperplasia, and increased auxin transport. In contrast, avp1-1 null mutants have severely disrupted root and shoot development and reduced auxin transport. Changes in the expression of AVP1 affect the distribution and abundance of the P-adenosine triphosphatase and Pinformed 1 auxin efflux facilitator, two proteins implicated in auxin distribution. Thus, AVP1 facilitates the auxin fluxes that regulate organogenesis.  相似文献   

木本植物木质部的空穴和栓塞化   总被引：1，自引：0，他引：1  

张硕新  ＨａｎｎｏＲｉｃｈｔｅｒ 《西北林学院学报》1996,(3)

本文从空穴和栓塞化对植物的危害，影响空穴和栓塞化的因素，植物体内的空穴及栓塞化的测定方法，栓塞的季节变化以及栓塞化木质部的恢复等五个方面综述了这方面的研究成果，认为木质部的栓塞化可影响植物的正常生长，但不会危及植物的存活；水分胁迫、冻害、病菌、机械胁迫、微生物引起的壁退化和纹孔膜的透性与空穴和栓塞的产生有关；最好将超声波法和“冲洗法”结合起来研究栓塞和空穴现象；应进一步搞清栓塞恢复机理  相似文献   

Soils of Eagle crater and Meridiani Planum at the Opportunity Rover landing site     

Soderblom LA  Anderson RC  Arvidson RE  Bell JF  Cabrol NA  Calvin W  Christensen PR  Clark BC  Economou T  Ehlmann BL  Farrand WH  Fike D  Gellert R  Glotch TD  Golombek MP  Greeley R  Grotzinger JP  Herkenhoff KE  Jerolmack DJ  Johnson JR  Jolliff B  Klingelhöfer G  Knoll AH  Learner ZA  Li R  Malin MC  McLennan SM  McSween HY  Ming DW  Morris RV  Rice JW  Richter L  Rieder R  Rodionov D  Schröder C  Seelos FP  Soderblom JM  Squyres SW  Sullivan R  Watters WA  Weitz CM  Wyatt MB  Yen A  Zipfel J 《Science (New York, N.Y.)》2004,306(5702):1723-1726

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.  相似文献   

Reduced North Atlantic deep water coeval with the glacial Lake Agassiz freshwater outburst     

Kleiven HK  Kissel C  Laj C  Ninnemann US  Richter TO  Cortijo E 《Science (New York, N.Y.)》2008,319(5859):60-64

An outstanding climate anomaly 8200 years before the present (B.P.) in the North Atlantic is commonly postulated to be the result of weakened overturning circulation triggered by a freshwater outburst. New stable isotopic and sedimentological records from a northwest Atlantic sediment core reveal that the most prominent Holocene anomaly in bottom-water chemistry and flow speed in the deep limb of the Atlantic overturning circulation begins at approximately 8.38 thousand years B.P., coeval with the catastrophic drainage of Lake Agassiz. The influence of Lower North Atlantic Deep Water was strongly reduced at our site for approximately 100 years after the outburst, confirming the ocean's sensitivity to freshwater forcing. The similarities between the timing and duration of the pronounced deep circulation changes and regional climate anomalies support a causal link.  相似文献   

How temperature and aridity drive lignin decomposition along a latitudinal transect in western Siberia     

Thao Thi Dao  Robert Mikutta  Birgit Wild  Leopold Sauheitl  Norman Gentsch  Olga Shibistova  Jörg Schnecker  Nikolay Lashchinskiy  Andreas Richter  Georg Guggenberger 《European Journal of Soil Science》2023,74(5):e13408

Climate change drives a northward shift of biomes in high-latitude regions. This might have consequences on the decomposition of plant litter entering the soil, including its lignin component, which is one of the most abundant components of vascular plants. In order to elucidate the combined effect of climate and soil characteristics on the decomposition pattern of lignin, we investigated lignin contents and its degree of oxidative decomposition within soil profiles along a climosequence in western Siberia. Soil samples were collected from organic topsoil to mineral subsoil at six sites along a 1500-km latitudinal transect, stretching from tundra, through taiga and forest steppe to typical steppe. The stage of lignin degradation, as mirrored by decreasing organic carbon-normalized lignin contents and increasing oxidative alteration of the remnant lignin (acid-to-aldehyde ratios of vanillyl- and syringyl-units [(Ac/Al)_V and (Ac/Al)_S]) within soil horizons, increased from tundra to forest steppe and then decreased to the steppe. Principal component analysis, involving also climatic conditions such as mean annual temperature and aridity index, showed that the different states of lignin degradation between horizons related well to the activity of phenoloxidases and peroxidases, enzymes involved in lignin depolymerization that are produced primarily by fungi and less importantly by bacteria. The low microbial lignin decomposition in the tundra was likely due to low temperature and high soil moisture, which do not favour the fungi. Increasing temperature and decreasing soil moisture, facilitating a higher abundance of fungi, led to increased fungal lignin decomposition towards the forest-steppe biome, while drought and high pH might be responsible for the reduced lignin decomposition in the steppe. We infer that a shift of biomes to the north, driven by climate change, might promote lignin decomposition in the northern parts, whereas in the south a further retardation might be likely.  相似文献