Photosynthetic light response curves determined with the leaf oxygen electrode: minimisation of errors and significance of the convexity term

From photosynthetic studies on a range of monocotyledonous (C-3 and C-4) and dicotyledonous (C-3) plants using a leaf oxygen electrode, we conclude the following. (i) A non-linear model [J.H.M.Thornley (1976) Mathematical models in plant physiology, Academic Press, London; B. Marshall and P.V. Biscoe (1980) J Exp Bot 31:29-39] significantly better describes the photosynthetic light response curve [rate of photosynthesis (P) versus incident photosynthetic photon flux density (I)] than the frequently used linear hyperbolic model [E.I. Rabinowich (1951) Photosynthesis and related processes, vol 2, Wiley, New York]. (ii) When used at the recommended CO2 partial pressures (Ca=1-5 kPa), CO2 supply saturates the photosynthesis rate in the C-3 dicot Phaseolus coccineus L. but not in the C-3 monocot Hordeum vulgare L.. (iii) Fits using a linear hyperbolic model for P versus I produce relatively large and statistically significant errors (,60%) in the estimation of Pmax and quantum efficiency (!) if Ca is not >5 kPa. (iv) The convexity term, Š, incorporated into the non-linear models for P versus I appears to reflect the limitation placed on the carboxylation processes by the supply of CO2 to the chloroplast stroma. Therefore, the use of a non-linear model providing an estimate of Š should be encouraged, as it is likely to provide information on the physiological status of plants

The relationship among children’s arithmetic problem solving, working memory, and planning ability.

本研究は小学生における算数問題解決，ワーキングメモリ（WM），プランニング能力の関連を検討した。小学6 年生48 名（12 歳）が調査に参加した。算数問題解決，WM 容量，プランニング能力の測度として，全国学力・学習状況調査に基づいた算数文章題（基礎問題，応用問題），リーディングスパンテスト，Porteus 迷路課題がそれぞれ用いられた。その結果，基礎的な文章題の遂行，WM，プランニング能力は応用的な文章題の遂行に有意に関連すること，そして，月齢と基礎的文章題の遂行を統制した場合でさえ，WM やプランニング能力の寄与が持続することが示された。また，WM の相対的に小さい児童は問題文の誤読や計算ミスをなす傾向があった。本データは，算数文章題の遂行におけるWM とプランニング能力の重要性を示している。This study examined the relationship among elementary student’s arithmetic problem solving, working memory (WM), and planning ability. Forty-eight 6th graders (12-year-olds) participated in this study. Arithmetic word problem based on national achievement test (basic problems and practical problems), reading span test, and Porteus maze test were used as the measures of arithmetic problem solving, WM capacity, and planning ability, respectively. The results showed that the achievement on basic word problem, WM, and planning ability were significantly related to the achievement on practical word problem, and that the contribution of WM and planning ability persisted even month old and the basic problem achievement were partialled out. Also, the results showed that the children with low WM tended to misread a problem statement and to mistake in calculation. The data showed the importance of WM and planning ability in the achievement on arithmetic word problems

A study of some characteristics of individual clones of Schistosoma mansoni with emphasis on the biological and metabolic activities

The variability within schistosome populations was explored using mixed populations of cercariae from multimiracidial snail infections and individual clones of Schistosoma mansoni cercariae obtained from monomiracidial snail infections. We investigated the heterogeneity between different clones of S. mansoni with respect to infectivity and metabolism. One difference between clones of cercariae was found in the recovery of adult worms from Balb/C mice. Recovery of adult worms was greater after infections with a mixed population than with a clonal population. To investigate some biochemical features of individuals in clones or mixed populations, the uptake of [35S]methionine into individual parasites and their membrane proteins was measured. Isoelectric focusing of a soluble membrane fraction: the frozen–thawed supernatant extracted from individual clones, showed the presence of proteins of isoelectric point between 7.2 and 8.2 in all clones. These proteins were less labelled with [35S]methionine in the clones than in the mixed population. It was concluded that basic proteins are synthesized by all clones and in the mixed population but at different rates. Differences in the rate of incorporation of [35S]methionine into the surface membranes of schistosomula and adult worms derived from individual clones are reported. In addition, a direct correlation between the percentage of recovery of adult worms from mice infected with individual clones of S. mansoni and the rate of incorporation of [35S]methionine into schistosomula of these particular clones was observed. It is suggested that the high rate of metabolism shown by an individual clone may account for the enhanced survival of the cercariae derived from that clone during penetration of the skin and migration through the vertebrate host. In order to examine individuals in a population of schistosomula, from a clone or mixed population, the lysosome-specific fluorescent probe LysoTracker DND-99 was used to label the parasites and quantitative fluorescent measurements were made on individual parasites. There were significant differences between clones and a mixed population. Furthermore, the variation between individuals from a mixed population was greater than from that in any clone, just as was found in the infectivity studies. Freshly transformed schistosomula of individual clones labelled with the LysoTracker DND-99 showed less variations in the quantitative uptake of the dye within a single clone when compared to the mixed population. We conclude that for any biochemical and biological parameter, a population of cercariae consists of individuals showing a wide range of values, with a much greater range in a mixed population. This variability is likely to have great relevance for infectivity of the final host and the efficacy of drugs and the immune system