Qualitative characterization of the endogenous cytokinins in red pine and aspects of their influence on seedling development

Red pine seedlings alternate between root and shoot production in a periodic fashion. This habit is referred to as episodic growth and is assumed to be controlled by endogenous plant growth regulators. This project was concerned with the role played by cytokinins in the control of episodic growth;After confirming the existence of episodic growth in red pine seedlings, a carrier solution was optimized and a series of exogenous application trials was conducted. Only those solutions containing a surfactant and N[superscript]6-benzylaminopurine (BAP) produced an observable response. Foliar applications of BAP induced the formation of an apical cluster of buds. As the BAP concentration was increased from 2.5 to 200 mg/l, there was a corresponding increase in the number of buds formed. Hypocotyl length and the percentage of the induced buds that elongated were inversely proportional to the BAP concentration used. The response to BAP, as affected by seedling age and application number, was also determined. The younger the seedlings were when they received their first BAP treatment and the more applications they received, the greater the reduction in hypocotyl growth. As the number of BAP applications increased, the number of buds formed was proportionately greater. As the age at which seedlings received their first treatment of BAP increased, the percentage of buds that elongated decreased. When the same carrier solution, containing 200 mg/l BAP, was applied to the potting mix in which the seedlings were grown, axillary bud development along the hypocotyl was promoted. Germinating seeds were also treated with the same solution. Longer exposure to BAP resulted in progressively shorter hypocotyls and needles and in lower survival;The origin of the buds induced by BAP was characterized histologically. The BAP treatments were found to induce precocious axillary bud development and adventitious bud formation. The suitability of this bud cluster for micropropagation of red pine was also explored;Because the CKs produced by red pine have never been identified, they were qualitatively characterized. The cytokinins produced by roots and shoots were identified based on the retention times of biological activity on Sephadex LH-20 and Spherisorb ODS-2. Zeatin and zeatin riboside (ZR) were both found in the basic fraction of root and shoot extracts. The presence of ZR in both tissues was confirmed by GC-MS analysis. Evidence for the presence of dihydrozeatin O-glucoside in the shoot basic fraction and for zeatin O-glucoside in the roots is also presented. Zeatin riboside monophosphate, isopentenyladenosine monophosphate (iPMP) and glucosyl phosphate derivatives were found in both root and shoot acidic fractions. The presence of iPMP in both tissues implies that cytokinin biosynthesis is occurring throughout the plant. Evidence suggesting the presence of a phosphorylated derivative of zeatin O-glucoside in the roots is presented

The Self-Pollination of Amur Honeysuckle

Amur honeysuckle (Lonicera maackii) poses a dire threat to the health of forests throughout the eastern United States. While self-pollination has been identified as an important trait of invasive plant species, this trait is understudied, and Amur honeysuckle is anecdotally described as lacking this characteristic. To examine the ability of Amur honeysuckle to self-pollinate, we selected 171 individual shrubs distributed across 9 sites. We compared the number of berries, seeds per berry, and seed germination rates of self- and cross-pollinated flowers by pairing branches covered with pollination bags prior to flower emergence with uncovered branches on the same individual shrub. Out of 171 individuals, 48 produced self-pollinated berries within pollination bags (28%), with 48% of bagged branches exhibiting necrosis due to increased temperature and humidity. Self-pollinated berries produced 1.5 ± 1.4 ( mean ± 1 SD) seeds per berry, whereas cross-pollinated berries produced 3.3 ± 1.5 seeds per berry. In a germination trial, 47.3% of self-pollinated seeds have germinated compared to 41.7% of crosspollinated seeds. This study has shown that Amur honeysuckle can self-pollinate and set viable seed, providing the species with an important mechanism to increase population abundance during early stages of invasion

The Association Between Rate and Severity of Exacerbations in Chronic Obstructive Pulmonary Disease: An Application of a Joint Frailty-Logistic Model.

Exacerbations are a hallmark of chronic obstructive pulmonary disease (COPD). Evidence suggests the presence of substantial between-individual variability (heterogeneity) in exacerbation rates. The question of whether individuals vary in their tendency towards experiencing severe (versus mild) exacerbations, or whether there is an association between exacerbation rate and severity, has not yet been studied. We used data from the MACRO Study, a 1-year randomized trial of the use of azithromycin for prevention of COPD exacerbations (United States and Canada, 2006-2010; n = 1,107, mean age = 65.2 years, 59.1% male). A parametric frailty model was combined with a logistic regression model, with bivariate random effects capturing heterogeneity in rate and severity. The average rate of exacerbation was 1.53 episodes/year, with 95% of subjects having a model-estimated rate of 0.47-4.22 episodes/year. The overall ratio of severe exacerbations to total exacerbations was 0.22, with 95% of subjects having a model-estimated ratio of 0.04-0.60. We did not confirm an association between exacerbation rate and severity (P = 0.099). A unified model, implemented in standard software, could estimate joint heterogeneity in COPD exacerbation rate and severity and can have applications in similar contexts where inference on event time and intensity is considered. We provide SAS code (SAS Institute, Inc., Cary, North Carolina) and a simulated data set to facilitate further uses of this method

JnCML-like, an EF-hand motif-containing gene seasonally upregulated in the transition zone of black walnut (Juglans nigra L.)

The economic value of a black walnut (Juglans nigra L.) tree is strongly determined by the quality and quantity of darkly colored heartwood in its stem. To understand the regulation of heartwood formation, we analyzed the region of heartwood formation in walnut stems (i.e., the transition zone, TZ) for the expression of 80 ESTs. Semi-quantitative RT-PCR and real-time PCR was performed to detect expression changes of candidate genes in the TZ and sapwood of trees harvested in summer and fall. Results revealed that the transcript of a clone containing two presumed EF-hand motifs was expressed at higher levels in the TZ than in other xylem tissues. Analysis of the full-length coding sequence revealed that the black walnut gene JnCML-like is similar to grancalcin-like calcium-binding EF hand proteins in Arabidopsis thaliana (At3g10300) and Zea mays (NM 001153810). A model of the predicted structure of JnCML-like showed it is similar to grancalcin and m-calpain, penta-EF-hand family proteins associated with cell proliferation, differentiation and programmed cell death. JnCML-like transcript was detected in tissue from the region of the pith meristem, and in roots, embryogenic callus, vascular cambium, female flowers, male flowers, green leaves, and partially and fully senescent leaves of black walnut, although transcript abundance varied considerably among these tissues