Realized gene flow within mixed stands of Quercus robur L. and Q. petraea (Matt.) L. revealed at the stage of naturally established seedling

The estimates of contemporary gene flow assessed based on naturally established seedlings provide information much needed for understanding the abilities of forest tree populations to persist under global changes through migration and/or adaptation facilitated by gene exchange among populations. Here, we investigated pollen‐ and seed‐mediated gene flow in two mixed‐oak forest stands (consisting of Quercus robur L. and Q. petraea [Matt.] Liebl.). The gene flow parameters were estimated based on microsatellite multilocus genotypes of seedlings and adults and their spatial locations within the sample plots using models that attempt to reconstruct the genealogy of the seedling cohorts. Pollen and seed dispersal were modelled using the standard seedling neighbourhood model and a modification—the 2‐component seedling neighbourhood model, with the later allowing separation of the dispersal process into local and long‐distance components. The 2‐component model fitted the data substantially better than the standard model and provided estimates of mean seed and pollen dispersal distances accounting for long‐distance propagule dispersal. The mean distance of effective pollen dispersal was found to be 298 and 463 m, depending on the stand, while the mean distance of effective seed dispersal was only 8.8 and 15.6 m, which is consistent with wind pollination and primarily seed dispersal by gravity in Quercus. Some differences observed between the two stands could be attributed to the differences in the stand structure of the adult populations and the existing understory vegetation. Such a mixture of relatively limited seed dispersal with occasional long distance gene flow seems to be an efficient strategy for colonizing new habitats with subsequent local adaptation, while maintaining genetic diversity within populations.     

Effects of simulated nitrogen deposition on growth and photosynthesis of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings

To study the impact of nitrogen deposition on 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in pots, the dissolved NH₄NO₃ was sprayed on the seedlings every 3 days for 1 year. The simulated elevated N depositions were equivalent to N0(0), N1(6 gN/(m² a)), N2(12 gN/(m² a)), N3(24 gN/(m² a)) and N4(48 gN/(m² a)). The results indicated that medium N treatments (N2, N3) enhanced growth significantly. The height, stem base diameter and per-seedling biomass of Chinese fir seedlings increased with N loads and decreased in the high N treatments. Compared to N0, the height and per-seedling biomass were highest in N2 treatment and increased by 10.77% and 12.35%, respectively. The stem base diameter was highest in N3 treatment and increased by 8.81% compared to N0. The net photosynthetic rate (Pn) in treatments N1, N2, N3, N4 increased by 1.20%, 9.28%, 24.23% and 4.30%, and the highest photosynthetic rate by 67.09%, 125.32%, 148.10% and 51.90%, respectively. The N1–N3 treatments, especially N2, stimulated light compensation point (LCP) of the seedlings significantly, but N4 exhibited inhibitive effect. Compared with LCP, light saturation point (LSP) showed weaker response to N loads, positive to N2, but negative to all other N treatments. Low-to-medium N treatments (N1, N2) enhanced Chl (a + b) by 2.19% and 37.15%, while medium-to-high N treatments (N3, N4) reduced Chl (a + b) by 7.95% and 15.56%, respectively. Water use efficiency (WUE) and stomatal conductance (C) decreased slightly with N loads.     

Effects of Planting Depth,Sediment Grain Size,and Nutrients on Ruppia maritima and Potamogeton perfoliatus Seedling Emergence and Growth

Protocols are now available for seed harvest, storage and germination of several mesohaline and polyhaline species; however, low seedling survival rates point to the need for an increased understanding of factors affecting seedling establishment. Depth of seed burial in sediments and initial seedling growth rates are shown to be limiting factors for photosynthetic competency of Ruppia maritima and Potamogeton perfoliatus. Seedling emergence is inversely proportional to planting depth on sediments ranging in grain size from coarse sands (850 μm) to silt (63 μm). Less than 6% of the seeds of either species emerged when buried to a depth of 3 cm in test sediments. Germination was greatest for seeds placed on the surface of sediments; however, these seedlings were subject to displacement because of the weak and fragile roots produced during early growth. Fine sediments may be more favorable for R. maritima seedling establishment, because seedling emergence and height decreased with increasing sediment grain size. Potamogeton perfoliatus seedlings seem to be more tolerant of a wider range of sediment grain sizes than R. maritima as indicated by the lack of an effect of sediment grain size on P. perfoliatus seed emergence, seedling height, and biomass. Increasing nutrients stimulated seedlings of both species; however, even at the highest concentrations tested, growth, as determined by shoot elongation and leaf and root formation, slowed within 7–10 days. This suggests factors other than mineral nutrients and light limit growth or that growth shifts from aboveground biomass production to belowground vegetative spread.     

硝酸镧对碱胁迫下黑麦草幼苗生长和光合生理的影响

在150 mmol·L^-1 NaHCO₃胁迫下,研究了不同浓度硝酸镧对黑麦草幼苗生长的影响及其对叶片光合生理响应的调节作用。结果表明,叶面喷施低浓度硝酸镧(0.05 mmol·L^-1)预处理显著减小了碱胁迫下黑麦草幼苗生物量、叶片叶绿素和类胡萝卜素含量、叶绿体希尔反应、光合电子传递、光合磷酸化、Mg²⁺ ATP酶、RuBP羧化酶活性和光合效率的下降幅度,却对光呼吸调节酶乙醇酸氧化酶活性无明显影响。而高浓度硝酸镧(0.5 mmol·L^-1)预处理不仅对碱胁迫没有缓解作用,反而加重了碱胁迫伤害。因此,适宜浓度硝酸镧可以通过改善光合功能从而缓解碱胁迫对黑麦草幼苗生长的抑制作用。     

He-Ne激光对小麦ROP GTPase经增强UV-B辐射造成的损伤的修复研究

采用He-Ne激光辐照对增强UV-B辐射后小麦幼苗ROP GTPase损伤修复作用进行了研究。采用了SDS-PAGE电泳法检测各组ROP GTPase的含量和激光共聚焦显微镜对小麦微丝进行FITC荧光强度标记的测定。研究结果表明：经增强UV-B辐射后,小麦幼苗的Rop GTPase含量降低,LCSM扫描细胞原生质体形状发生改变,细胞骨架受到破坏,其被标记的荧光变暗,强度减弱,在整个UV-B处理期间均低于对照组（CK）,再以He-Ne激光处理后,其含量,形状和强度均有所提高,但仍低于对照组。由此说明,UV-B辐射能使小麦幼苗的Rop GTPase含量下降,微丝骨架受到破坏,一定剂量的激光对UV-B辐射后小麦的蛋白含量和细胞骨架有一定修复作用。Rop GTPase参与了微丝骨架重组的过程。     

一年生陆地棉细胞核雄性不育系洞A的宿生栽培效应

植物细胞核雄性不育系具有易于恢复但保持困难的特点。根据广西南部冬季无霜冻的气候特点,在广西南宁进行了一年生陆地棉细胞核雄性不育系洞A的三年露地栽培。结果表明:二、三年生洞A在5月上旬开花、6月下旬吐絮,这是一年生洞A在相同环境条件下难以达到的;与一年生洞A相比,二、三年生洞A的子指、单株铃数、产量显著增加,但单铃重、衣分显著下降,僵瓣率显著增加;纤维品质基本没有显著变化。说明利用陆地棉细胞核雄性不育系在南亚热带的宿生栽培进行良种繁育具有较好的前景。     

土壤干旱胁迫对毛鸡骨草幼苗生长及某些生理特性的影响

以毛鸡骨草幼苗为试验材料,测定毛鸡骨草在不同水分条件下的生长状况和相关的生理生化指标,结果表明:随着干旱胁迫的增加,毛鸡骨草幼苗的株高、茎粗、复叶长等呈递减趋势,根直径、须根数呈递增趋势;根、叶片脯氨酸含量和叶片可溶性糖的含量均呈先降低再上升的趋势,水势随干旱胁迫的加剧呈先上升后降低的趋势,根系活力随干旱胁迫的加剧呈递减趋势。但是,在严重干旱胁迫下,各生长指标的增长均受到明显的抑制。     

(NH4)2SO4对瓜尔豆幼苗在不同光照下耐冷性的影响

通过温室穴盘育苗试验,研究叶面喷施(NH₄)₂SO₄对低温胁迫12 h后不同光通量密度（PFD）条件下,瓜尔豆幼苗在常温培养过程中幼苗生存及叶片SOD活性、POD活性和MDA含量的影响。结果表明：低温处理一夜后,在温室自然光照（强光）下进行常温恢复时,瓜尔豆叶片中SOD和POD活性始终显著低于对照,MDA含量显著高于对照,幼苗死亡率显著高于对照;在90 μmol·m^-2·s^-1弱光下恢复2～4 d后,叶片中保护酶活性显著高于对照,MDA含量保持较低水平,幼苗均正常生长。叶面喷施(NH₄)₂SO₄能显著提高低温处理后的植株叶片抗氧化酶类活性,减少叶片中MDA的产生,降低幼苗死亡率,0.2% (NH₄)₂SO₄处理效果最好,其次为0.4%(NH₄)₂SO₄。短期低温后,使植物处在弱光环境下能减少活性氧的发生,为植物抗氧化系统达到新的平衡提供有利条件,从而减轻甚至消除低温伤害。     

Isolation and characterization of resistance and defense gene analogs in cotton (Gossypium barbadense L.)

Plant disease resistance gene (R gene) and defense response gene encode some conserved motifs. In the present work, a PCR strategy was used to clone resistance gene analogs (RGAs) and defense gene analogs (DGAs) from Sea-island cotton variety Hai7124 using oligonucleotide primers based on the nucleotide-binding site (NBS) and serine/threonine kinase (STK) in the R-gene and pathogenesis-related proteins of class 2 (PR2) of defense response gene. 79 NBS sequences, 21 STK sequences and 11 DGAs were cloned from disease-resistance cotton. Phylogenic analysis of 79 NBS-RGAs and NBS-RGAs nucleotide sequences of cotton already deposited in GenBank identified one new sub-cluster. The deduced amino acid sequences of NBS-RGAs and STK-RGAs were divided into two distinct groups respectively: Toll/Interleukin-1 receptor (TIR) group and non-TIR group, A group and B group. The expression of RGAs and DGAs having consecutive open reading frame (ORF) was also investigated and it was found that 6 NBS-RGAs and 1 STK-RGA were induced, and 1 DGA was up-regulated by infection of Verticillium dahliae strain VD8. 4 TIR-NBS-RGAs and 4 non-TIR-NBS-RGAs were arbitrarily used as probes for Southern-blotting. There existed 2–10 blotted bands. In addition, since three non-TIR-NBS-RGAs have the same hybridization pattern, we conjecture that these three RGAs form a cluster distribution in the genome.