Spikelet Sterility and Flowering Response of Rice to Water Stress at Anthesis

Water deficits at the anthesis stage of rice (Oryza sativa L.)induce a high percentage of spikelet sterility and reduce grainyield. This study attempted to elucidate the direct effectsof water stress on panicle exsertion, spikelet opening, andspikelet desiccation leading to spikelet sterility. A well-wateredtreatment and two water stress levels were imposed in pot-grownplants of IRAT 13 (upland cultivar) and IR20 (lowland cultivar)at the time of flowering under greenhouse conditions A cultivar difference was observed in the flowering responseto water stress with a high sensitivity in IR20. The time courseof panicle exsertion showed an inhibitory effect due to thelow panicle water status. Low panicle water potentials significantlyreduced the number of opened spikelets. Spikelet opening wascompletely inhibited at panicle water potentials below –1·8MPa and –2·3 MPa in IR20 and IRAT 13, respectively.However, the peak spikelet opening time in a day was not influencedby the stress treatment. Spikelets in stressed panicles wereobserved to remain open for a longer period than in the well-wateredpanicles. The role of turgor in spikelet opening is also discussedin the study. At low panicle water potentials, severe desiccationof spikelets and anthers was noted. The deleterious effectsof water deficits on spikelet opening and spikelet water losscontributed to reduced spikelet fertility Oryza sativa L., rice, spikelet sterility, flowering, water stress, panicle water potentials, turgor potentials, desiccation     

Motion Analysis in the Assessment of Surgical Skill

Abstract

Manual skill is now widely recognised as an important aspect of training in surgery. However, measurement of the skill of a surgeon has in the past been rather subjective in nature, relying on the judgement of experts in the analysis of videotapes. Objective measurements can be made by analysing the velocities of a surgeon's hands during a procedure. In particular, we have found that the number of movements made during a typical procedure will decrease as the surgeon's skill increases. Velocity traces display purposeful movements corrupted by uncorrelated noise from sources such as hand tremor and measurement artefacts. However, we have found that it is possible to filter the noise effectively. Furthermore, we have shown that the skill measurement obtained by counting movements is highly robust to over or under filtering.     

Development and use of anchored‐SSRs to study DNA polymorphism in bread wheat (Triticum aestivum L.)

In bread wheat, 21 anchored simple sequence repeat (SSR) primer pairs detecting SSR length polymorphism and 42 anchored SSR primers detecting microsatellite‐anchored fragment length polymorphisms (MFLPs) are reported. Eight bread wheat genotypes were used for detecting polymorphism. The number of alleles in SSR analysis ranged from two to six, with a mean of 2.9 alleles per SSR. The number of polymorphic bands in MFLP ranged from two to 40, with a mean of 12.74 polymorphic bands/primer combination, the SSRs with CT/GA motifs giving the highest level of polymorphism (a mean of 18.37 bands). The average value of polymorphic information content (PIC) was 0.473 for SSRs and 0.061 for MFLP.     

IN VITRO EFFECT OF HORMONES ON THE BARK OF PLUMERIA RUBRA LINN. VAR. ACTUIFOLIA BAILEY

Young bark (with cambium) of Plumeria rubra Linn. var. acutifolia Bailey was cultured in solid media (i) without hormone, (ii) Kinetin (K), (iii) with GA₃ and (iv) with IAA at concentrations of 0.05, 0.10, 0.15 and 0.20 mg per litre. The nutrients of the media were fed laterally through the cambium zone. The amount of the phloem zone was increased considerably by GA₃, less by K and IAA. The lignified secondary wall of the pericyclic living fibres was dissolved by each of the hormones. Sieve tube member length decreased in all treatments, more in higher concentrations. K decreased the frequency of sieve tubes (most at 0.10 mg/α) and increased the frequency of parenchyma cells (optimum at 0.10 mg/α). GA₃ also favoured formation of parenchyma cells and decrease of the frequency of sieve tubes, progressively with the increase of concentration. IAA also increased the parenchyma cell frequency progressively with concentration and decreased slightly the sieve tube frequency. IAA and GA₃ increased ray frequency and decreased parenchyma cell diameter, much at high concentration. But K had less effect on ray frequency and increased parenchyma cell diameter progressively with concentrations.     

Post-embryonic development of water- and airbreathing organs of Anabas testudineus (Bloch)

The development of respiratory surfaces in post-embryonic stages of Anabas testudineus was studied using morphometric methods on serial sections through the pharyngeal region of specimens obtained by induced breeding of known parentage. The larvae and fry were fixed in glutaraldehyde and osmium tetroxide. In the young stages aquatic respiration was found to be obligatory. The hatchlings come out of the egg membranes about 10 h after fertilization. During the yolk-sac stages gaseous exchange takes place through the well vascularized skin. The gills start differentiating at about 24 h and become functional at about 39 h. The labyrinthine organs begin to develop after 51 h but the hatchlings do not take an air breath until they reach 13–14 days. The appearance of scales at 11–14 days probably hinders cutaneous respiration and is correlated with the onset of aerial respiration.
Morphometric analysis using stereological methods shows high surface: volume ratios for the gills and labyrinthine organs as adaptations to gas exchange function. A marked decrease in surface: volume ratio for the suprabranchial cavities between 7 and 11 days indicates an increase in volume to accommodate the expanding labyrinthine plates which retain a fairly constant surface: volume ratio.