Leaf area measurements are required in several agronomical studies. Usually, there is an interest for measurement methods that are simple, quick and that will not destroy the leaf. The objectives of this work were to evaluate leaf area (y), length (l) and width (w) of 20 half-sibling progenies of custard apple tree (Annona squamosa L.), and to fit regression equations of the type y = a + bx, where x = l.w, that will allow y to be estimated based on l and w. The experiment was conducted as random blocks with five replicates and four plants per plot. Five mature leaves were randomly collected from each plant. Leaf area was measured with an automatic measuring device and leaf dimensions were determined with a ruler. All values of b were different from zero. Differences occurred only in 11% of the 190 possible comparison pairs between progenies, with regard to the estimates of b. No differences were observed between progenies with respect to leaf length, width and area. In view of this fact, the equation y = 0.72 x (R² = 0.77) was fitted for all progenies.

We provide the most comprehensive description of student segregation in the Portuguese public school system to date, a system that exhibits interesting institutional features potentially linked with the student segregation issue (e.g. school catchment areas, course tracking, and almost no central regulations regarding class composition). The analysis uses the entire regular student population enrolled in all public schools of continental Portugal (grades 1 to 12, from 2006/07 to 2016/17). Looking at three segregation dimensionseconomic, academic, and immigrantat both between and within-school levels, and using a novel dissimilarity index recently proposed in the literature aimed at better capturing systematic segregation, we find that segregation, on median, is mild, across time, grades, and regions. The most important exception is the case of within-school academic segregation. During upper-secondary schooling, in particular, when students are divided across classes according to own course-tracking decisions, it doubles. Moreover, within-school academic segregation estimates have the largest interquartile ranges, within a given year, grade, or region, pointing to heterogeneity in the way different schools set up classes internally in terms of students' academic characteristics. Academic and economic segregation are positively associated, at both between and within school levels. The Portuguese segregation insights are also compared to those from other geographies. and Castelo Branco; "north" -Viana do Castelo, Braga, Vila Real, Bragança, Guarda, Viseu, and Aveiro.

We analyze the effects of several class compositional dimensions on individual student achievement. We make use of a rich dataset that allows tackling major endogeneity concerns stemming from non-random allocation of students between and within schools. We find that increasing the percentage of high achievers in a 6 th grade class has a negative effect on student performance, while in a 9 th grade class the effect is in general non-significant. Students with no past retentions do better with an increasing proportion of this same type of classmate. Larger shares of low-income classmates hurt performance in general. Apart from the past retention dimension in which there is evidence supporting students' tracking, along all other compositional dimensions each class should reflect the respective school-grade population heterogeneity. Class composition rearrangements are estimated to provide a larger increment to performance than comparable reductions of class size.