Irreconcilable differences: fine-root life spans and soil carbon persistence

The residence time of fine-root carbon in soil is one of the least understood aspects of the global carbon cycle, and fine-root dynamics are one of the least understood aspects of plant function. Most recent studies of these belowground dynamics have used one of two methodological strategies. In one approach, based on analysis of carbon isotopes, the persistence of carbon is inferred; in the other, based on direct observations of roots with cameras, the longevity of individual roots is measured. We show that the contribution of fine roots to the global carbon cycle has been overstated because observations of root lifetimes systematically overestimate the turnover of fine-root biomass. On the other hand, isotopic techniques systematically underestimate the turnover of individual roots. These differences, by virtue of the separate processes or pools measured, are irreconcilable.     

Auxin effects on the mobility of kinetin in the plant

Kinetin (6-furfurylaminopurine) is generally considered to be relatively immobile within plants. Kinetin labeled with (14)C was applied to the stumps of decapitated bean plants, with or without simultaneous application of indoleacetic acid. Significantly greater amounts of kinetin moved downwards in the stem in the presence of added indoleacetic acid than in its absence.     

Draft genome of the filarial nematode parasite Brugia malayi

Parasitic nematodes that cause elephantiasis and river blindness threaten hundreds of millions of people in the developing world. We have sequenced the approximately 90 megabase (Mb) genome of the human filarial parasite Brugia malayi and predict approximately 11,500 protein coding genes in 71 Mb of robustly assembled sequence. Comparative analysis with the free-living, model nematode Caenorhabditis elegans revealed that, despite these genes having maintained little conservation of local synteny during approximately 350 million years of evolution, they largely remain in linkage on chromosomal units. More than 100 conserved operons were identified. Analysis of the predicted proteome provides evidence for adaptations of B. malayi to niches in its human and vector hosts and insights into the molecular basis of a mutualistic relationship with its Wolbachia endosymbiont. These findings offer a foundation for rational drug design.     

ULTRASONOGRAPHIC DIAGNOSIS-SMALL BOWEL INFARCTION IN A CAT

An 8-year-old, domestic short hair cat with a known history of hypertrophic cardiomyopathy and previous aortic thromboembolism was presented for 24 h of vomiting and pyrexia. Initial abdominal radiographs were unremarkable. On an upper gastrointestinal series, delayed gastric emptying and prolonged small intestinal transit time were found. An initial abdominal ultrasound revealed a focal region of aperistaltic small intestine with mild wall thickening, however, intestinal wall layering in this area appeared normal. By 72 h, there was a diffusely hypoechoic portion of thickened small bowel (0.51 cm) with loss of the normal layering and hyperechoic mesentery surrounding this segment of bowel. A small bowel infarction and focal peritonitis were suspected and confirmed at surgery.     

Variation in tracheid length in blue pine (Pinus wallichiana A. B. Jackson)

Summary Radial pattern of variation in the first-formed earlywood tracheid length in blue pine shows that it increases outwards from the pith at first rapidly up to the 10th ring, then more slowly up to about the 40th ring and thereafter it remains more or less constant. It is correlated significantly and positively with both age and distance from the pith up to 40 years. In the mature wood zone i.e. after 40 years, tracheid length is not affected by either age or distance from the pith. The mean tracheid length of mature wood is significantly and positively correlated with the mean tracheid length of juvenile wood and also with the tracheid length of each of the juvenile wood rings. Based on the results of this study some guidelines for sampling are proposed. Trees with greater than 51 cm d.b.h. or above 40 years of age can be compared by sampling only four outermost consecutive mature wood annual rings; and those with less than 51 cm d.b.h. or below 40 years of age can be compared by sampling any of the juvenile wood rings.A part of Ph. D. thesis submitted to Himachal Pradesh University, Simla-171 005 (India), under the supervision of Dr. K. K. Jain, Associate Professor. The author is thankful to Dr. Jain for constant encouragement and to the University Grants Commission (India) for financial assistance     

The effect of carbon and nutrient loading during nursery culture on the growth of black spruce seedlings: a six-year field study

We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling⁻¹) or an exponential nutrient loading regime (75 mg N seedling⁻¹). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO₂ (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading.     

Yield,nodulation, and N2 fixation by cowpea cultivars at different phosphorus levels

A greenhouse experiment was conducted to investigate the effect of a P application (0 vs. 50 mg P kg^-1) on yield, nodulation, and N₂ fixation by three cowpea cultivars (Soronko, Amantin, and IT81D-1137) using the ¹⁵N isotope-dilution method. When P was not applied the inoculated cowpea genotypes showed significant differences (Soronko>Amantin> IT81D-1137) in N accumulation, in contrast to the uninoculated cowpea cultivars, which accumulated similar amounts of N. The differences in shoot N in inoculated plants were thus caused by differences in N₂ fixation. The average values of N fixed (for both P levels) were 74% in Soronko, 59% in Amantin, and 42% in IT81D-1137, corresponding to 80, 51, and 24 mg N plant^-1, respectively. Inoculation increased the total shoot-N accumulation in cv. Soronko by 270% without P and by 204% with P, cv. Amantin by 152 and 104%, and cv. IT81D-1137 by 74 and 58%, respectively. With P, the % N derived from atmosphere (%Ndfa) was 42% for IT81D-1137, 62% for Amantin, and 76% for Soronko. The high value for Soronko indicates that in a soil of medium fertility, certain cowpea cultivars are capable of satisfying their total N requirement through N₂ fixation. The P effect on N₂ fixation was mainly in the total amount of N fixed rather than on the percentage derived from the atmosphere.     

Double ureters with ureteral ectopia in a domestic shorthair cat

A 5-month-old domestic shorthair cat was presented for evaluation of urinary incontinence since birth. Excretory urography revealed dilated double ectopic ureters draining a hydronephrotic right kidney. Urine culture yielded a pure culture of Klebsiella pneumoniae. The cat was treated initially with bactericidal antibiotics, followed by right-sided nephroureterectomy. The surgery and antibiotic therapy led to complete resolution of urinary incontinence and urinary tract infection. Ureteral duplication is an unusual congenital anomaly that has not been previously reported in the cat.