The role of ethylene and darkness in accelerated shoot elongation of Ammophila breviligulata upon sand burial

The impact of elevated ethylene concentrations and darkness on the growth and development of shoot organs of Ammophila breviligulata was investigated under experimental conditions in a complete two-way design. The results were compared with data of partially sand buried plants. Enhanced ethylene concentrations and sand burial stimulated the formation of new stem nodes, a prerequisite for burial-induced shoot elongation. However, internode elongation itself could not be promoted by the phytohormone ethylene, by darkness, or by their interaction. Sand burial inhibited the formation of rhizomes and tillers and the investment in root and rhizome biomass. Darkness mimicked this effect for the number of rhizomes and the biomass allocated to roots and rhizomes, indicating that the change in light regime upon sand burial may play an important role in the signal transduction chain that leads to a different allocation pattern in A. breviligulata. The results are discussed within the context of alternative signals that might initiate the internode elongation response in sand-buried A. breviligulata plants. Received: 5 July 1997 / Accepted: 28 February 1998     

The response of Ammophila breviligulata and Spartina patens (Poaceae) to grazing by feral horses on a dynamic mid-Atlantic barrier island

Ammophila breviligulata, American beachgrass, and Spartina patens, salt meadow hay, have been grazed by feral horses on the dunes of Assateague Island for hundreds of years; however, because of a significant increase in the horse population since the 1960s, overgrazing and dune erosion have become problems. Grazing was assessed on foredunes of four different morphologies along a 21-km stretch of the Maryland portion of the island using 17 exclosure plot pairs. In addition to decreased cover and biomass of the two species, plant structure was significantly affected by grazing. Leaf length and width, stem diameter, and stem density of A. breviligulata and stem diameter of S. patens were reduced in the grazed plots. Especially sensitive to grazing were reproductive characteristics. Percentage of plants in flower, height of flowering stems, and inflorescence length were all significantly reduced by grazing (nongrazed individuals measured). Species composition was not affected by horse accessibility.     

The role of carbohydrate reserves in the growth, resilience, and persistence of cabbage palm seedlings (Sabal palmetto)

Sabal palmetto (Walt.) Lodd. ex Schultes (cabbage palm) is an arborescent palm common in many plant communities throughout Florida, U.S.A., and the Caribbean. Although its seedlings grow very slowly in forest understories, they survive damage and defoliation well, and the species may increase in dominance following disturbances such as fire, logging, and hurricanes. We investigated the potential importance of total nonstructural carbohydrate (TNC) pools in the ability of cabbage palm seedlings to recover from the loss of aboveground tissue such as that caused by fire, grazing, or shallow burial by storm debris. TNC concentrations in belowground organs of seedlings from a forest understory were high, and TNC pools were sufficient to theoretically replace >50% of a seedling's canopy. The largest fraction of the belowground TNC pool was in stem tissue, where TNC in unclipped plants accounted for 26–54% of stem dry mass. Experimental reduction of TNC pools by repeated defoliation slowed seedling regrowth, and seedlings with inherently smaller pools (smaller seedlings) suffered higher mortality after repeated defoliation than did larger seedlings. Although regrowth and recovery after the loss of aboveground tissue was related to the size of the TNC pool in belowground organs, even the smallest seedlings with the smallest pools had sufficient stores to withstand at least two defoliations at frequent (7-week) intervals. Large belowground TNC pools in S. palmetto seedlings appear to enable them to survive all but the most frequent defoliations (e.g., frequent grazing or mowing). Allocation of resources to these stores, however, may contribute to the slow growth rates of S. palmetto seedlings in natural communities. Received: 13 April 1998 / Accepted: 28 August 1998     

Genetic Structure of Threatened Native Populations and Propagules Used for Restoration in a Clonal Species,American Beachgrass (Ammophila breviligulata Fern.)

An important goal of native plant restorations was to reconstitute populations that are genetically similar to native ones, thereby increasing the probably of successful establishment and persistence. We examined the extent to which this goal has been accomplished in Great Lakes restorations of Ammophila breviligulata Fern., a beachgrass species that is widely used for habitat restoration and is considered threatened in the study areas. In parallel studies on Lake Michigan and Lake Superior, we used polymorphic Intersimple Sequence Repeat markers to assess genetic similarity between well‐established and new native populations, restored populations, and restoration propagules obtained from two commercial suppliers. Native populations were generally more diverse than expected for a clonal species, whereas the commercially cultivated releases were monotypic. One of the commercial releases used in Minnesota was exclusively found in restored populations and did not occur in any other native population at this site. The propagules used in the newly planted restoration in Illinois were derived from a release that commercial suppliers maintain was derived from a native Michigan population, as opposed to a selected release. Diversity in this restoration was equivalent to that native Illinois’ populations; however, many of the genotypes were not of local origin. Overall, study underscores the importance of obtaining baseline genetic surveys of remnant native populations and restoration propagules before restoration efforts are initiated, especially when the populations are threatened or endangered.     

The relationship between the growth retardative effect of CCC and ethylene production

The ethylene production of the hypocotyls of CCC-treated bean plants was studied, and it was concluded that the treatment induced changes in the quantity of ethylene produced by the apical and basal hypocotyl parts. The ethylene production of the basal hypocotyl parts showed considerable increase on the effect of the treatment, in comparison with the control. The obtained results suggest a possible relationship between the longitudinal-growth inhibiting, stem-thickness inducing, root-formation stimulating effects of CCC and the effect exerted on ethylene production.     

沙鞭(禾本科)种子在沙丘上的萌发策略及幼苗的耐干燥特性

沙鞭是鄂尔多斯高原流动沙丘上分布的多年生禾草。对位于沙层不同深度的种子萌发和幼苗出土进行了测定。结果表明 ,种子的萌发和幼苗的出土随着沙埋深度的增加而减少 ,最高的幼苗出土率来自 0 .5～ 2 .0 cm浅层沙埋的种子 ,并且沙埋的深度影响种子萌发的时间。沙埋越深 ,越多的种子不能萌发并且处于强迫休眠的状态。但是 ,当被埋较深种子上层的沙层被移走使种子位于较浅的沙层时 ,种子能够克服强迫休眠。种子的强迫休眠还能够通过改善沙层中的空气含量来克服。在自然生境中 ,沙丘的流动性能够使萌发后的幼苗整个暴露在空气中遭受干旱胁迫 ,或者萌发后的幼苗在因无后续的降雨而变干。但是 ,沙鞭在幼苗的早期具有忍受干燥 ,在下次水合后能够恢复生长的能力。幼根的长度和干燥时间影响幼苗的生长恢复率     

The effects of spermidine biosynthetic inhibitor methyl bis-(guanylhydrazone) on spore germination,growth and ethylene production in Alternaria consortiale

The spermidine synthesis inhibitor methyl bis-(guanylhydrazone) was found to reduce spore germination, hyphal and mycelial growth in Alternaria consortiale. The addition of spermidine to the culture medium resulted in a promotion of growth. Methyl bis-guanylhydrazone and spermidine did not change ethylene production.The data suggest that spermidine plays a role in the development of Alternaria consortiale independent of ethylene.Abbreviations MGBG methyl bis-(guanylhydrazone) - SPD spermidine - ACC 1-aminocyclopropane-1-carboxylic acid - PDA potato dextrose agar     

Effect of brassinolide on callus growth and regeneration in Spartina patens (Poaceae)

The effect of brassinolide (BL) on cultured calluses of Spartina patens (Ait.) Muhl. (Poaceae), a halophyte monocot was studied. BL at 0.03–0.04 mg l^–1 at fixed concentrations of IAA (0.2 mg l^–1) and BA (3.0 mg l^–1) added in MS medium increased the ratio for fresh weight (CIRFW) to dry weight (CIRDW) by 96–111% and 235–326%. Similarly, in callus regeneration capacity, BL at 0.03 mg l^–1 was most effective, increasing the shoot regeneration ratio (SRR) by 425%. BL at 0.04 mg l^–1 had not such an increasing effect as BL at 0.03 mg l^–1, which increased SRR by 79%. However, BL at 0.005 mg l^–1 promoted regenerated shoot growth most significantly, increasing the shoot height increasing ratio (SHIR) by 395% after a 40-day culture. BL at 0.05 mg l^–1 was least effective in the callus regeneration and regenerated shoot growth, decreasing SRR by 27% and SHIR by 52%. Present results suggest that BL at 0.03 mg l^–1 is suitable for the callus growth and shoot regeneration, while BL at 0.005 mg l^–1 effectively enhanced the regenerated shoot growth.     

Poly(ethylene terephthalate) (PET) degradation by Yarrowia lipolytica: Investigations on cell growth,enzyme production and monomers consumption

The development of technologies for poly(ethylene terephthalate) (PET) depolymerization, such as biocatalysis, has been pointed as a very promising alternative to chemical hydrolysis processes. This work aims to understand the behavior of Yarrowia lipolytica, a robust yeast for diverse applications, in the presence of molecules from the PET production chain such as monoethylene glycol (MEG), terephthalic acid (TPA), bis (2-hydroxyethyl) terephthalate (BHET), PET oligomers, amorphous PET and post-consumer PET. The yeast was cultivated in rich media with and without glucose addition, in order to compare monomers release or consumption. TPA and MEG were consumed more intensely in the absence of glucose. The addition of the diester BHET yielded a 3-fold increased lipase production both at 160 rpm (118 U/L) and 250 rpm (385 U/L). In addition, 250 rpm agitation also provided a higher consumption of TPA (26% increase). The mono(2-hydroxyethyl) terephthalate (MHET) was the main intermediate released during polymer hydrolysis, followed by TPA and BHET. Thus, the use of Yarrowia lipolytica, which is capable of catalyzing the PET hydrolysis is of great potential to reduce the environmental impacts caused by unappropriated disposal of packages.     

The ancestry of Hordeum depressum (Poaceae, Triticeae)

Based on morphological, cytological, and molecular data, three diploid Hordeum species have by various authors been suggested to may have participated in the ancestry of the tetraploid H. depressum . In order to test the different hypotheses we undertook hybridizations between the proposed taxa, H. brachyantherum ssp. californicum, H. intercedens , and H. pusillum . Autoploids and amphiploids were achieved by treatment of young shoots with colchicine. These were then hybridized with H. depressum and the resulting hybrid plants were tested for fertility. The results strongly indicate that H. depressum arose as a consequence of hybridization between H. brachyantherum ssp. californicum and H. intercedens , probably with H. brachyantherum ssp. californicum as the female parent.     

The effect of waterlogging on the growth and ethylene content of Eucalyptus robusta Sm. (Swamp Mahogany)

Summary When waterlogged over a period of 80 days plants of Eucalyptus robusta Sm. showed symptoms of leaf chlorosis, epinasty and premature abscission, reduction of stem elongation, stem hypertrophy and formation of adventitious shoots; chlorophyll content was reduced and soluble protein content of the upper leaves increased. Waterlogging doubled the rate of release of ethylene from roots and stems within 6 days, but had no effect on the ethylene concentration of leaves.     

Effects of salinity on growth and cation accumulation of Sporobolus virginicus (Poaceae)

Optimal growth of euhalophytes requires moderate concentrations of salt and, in dicotyledons, is associated with succulence and accumulation of Na(+) in plant tissues. However, reports of salt-stimulated growth in monocotyledons are rare. Relative growth rate (RGR), biomass accumulation, and water content were studied in Sporobolus virginicus (Poaceae), a C(4) chloridoid grass, grown hydroponically with different concentrations of NaCl. Cation concentrations were determined by atomic absorption spectrophotometry. Optimal growth occurred at 100-150 mmol/L NaCl and was not dependent on nitrogen levels or accompanied by accumulation of Na(+) in leaves. Biomass accumulation and RGR in plants grown at 450 mmol/L NaCl were greater than in plants grown at 5 mmol/L. The Na?:?K ratios were lower in leaves than in roots, indicating discrimination in Na(+) and K(+) transport. Secretion of Na(+) increased from 166.5 to 336.7 mmol · g(-1) dry biomass · d(-1) as the NaCl concentration of the nutrient solution increased from 125 mmol/L to 450 mmol/L. Water concentrations of leaves and shoots were significantly greater in plants grown at optimal levels of salinity than in plants grown at lower or higher salinities. These results demonstrate salt-stimulated growth in a monocotyledon.     

Effect of red radiation, kinetin and linuron on growth and ethylene production in Chlorella

Both short-term and continuous red radiation stimulated while far red radiation inhibited growth and ethylene production in Chlorella pyrenoidosa. Kinetin and linuron also affected culture density and ethylene production, depending on their concentration. Phytochrome might participated in the regulation of growth and ethylene production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Antibiotic production, accumulation of intracellular carbon reserves, and sporulation in Micromonospora echinospora (ATCC 15837)

The physiology of the actinomycete Micromonospora echinospora was examined during growth. Biphasic accumulation of glycogen occurred, initially during the early exponential growth phase, and again following the onset of sporulation at 120 h. Lipid levels increased during growth eventually representing 25% of the cell mass. A significant proportion of the lipid was found to be in the form of triacylglycerols, which were found to accumulate markedly during the sporulation phase. The disaccharide trehalose was also found to accumulate during growth with levels rising to 5% of the dry weight during the mycelial production phase, then remaining constant during sporulation. Antibiotic was produced transiently by the cultures over the period preceding sporulation.     

Impact of growth form and carbohydrate reserves on tolerance to simulated deer herbivory and subsequent recovery in Liliaceae

? Premise of the study: Over-browsing of the understory vegetation by white-tailed deer has been a cause of decline in many plant populations. Liliaceae are particularly sensitive, yet individual species differ in their tolerance to deer herbivory. In this paper, we examine whether differences in clonal habit, carbon allocation patterns, and phenology influence the capacity of a species to tolerate and recover from repeated herbivory. ? Methods: Flowering ramets of Clintonia borealis, Maianthemum canadense, and Trillium erectum were subjected to total defoliation for one or two springs. ? Key results: Survival was highest in the nonclonal species, T. erectum, most probably due to its very large carbohydrate reserves. Nutrient reserves were less affected than carbohydrate reserves by defoliation, confirming the importance of carbohydrate reserves for survival. However, faster recovery following episodes of defoliation was observed not in the species that sprouted the earliest, T. erectum, but in the clonal species, M. canadense, which had the smallest carbohydrate reserves but also a lower shoot to root ratio than the other clonal species, C. borealis. All plants that were defoliated for 2 years only partially recovered in terms of leaf area, plant biomass, and carbohydrate and nutrient reserves, confirming the overall sensitivity of these species to simulated deer herbivory. ? Conclusions: High carbohydrate reserves and consequently low shoot to root ratios appear to increase tolerance to herbivory, whereas clonal species recover faster than nonclonal species. The role played by carbohydrates reserves suggests that these species could benefit from slightly higher light conditions in areas subjected to high deer pressure.