Testing Taylor's Power Law association of maize interplant variation with mean grain yield

Plant-to-plant variability is a crop stability component. The objective of this study in maize (Zea mays L.) was to test the validity of the theoretical background of the hypothesis that the coefficient of variation (CV) for grain yield per plant and mean yield are connected exponentially, following the Taylor's Power Law (TPL) Model. Field experimentation was conducted across two sites, two seasons, and two planting densities. Densities were the main plots, corresponding to the typical practice of 8.89 plants m^–2 (TCD) and the low-input optimal of 5.33 plants m^–2 (LCD), while hybrids were the subplots. Data from 26 subplots in the first site averaged CV values of 22.6% at the TCD and 21.9% at the LCD, and mean yields of 19.1 and 13.9 t ha^–1, respectively, following the TPL Model. The same was true for the second site, with average CVs and means of 41.5% and 14.3 t ha^–1 at the TCD and 36.8% and 11.5 t ha^–1 at the LCD. A test was performed on the simple correlation between the logarithms of variances and their respective means to investigate whether there is a systematic variance dependence on mean, thus questioning the reliability of TPL. The validity of TPL was verified in the first site. Nevertheless, there was a systematic dependence of yield variance on mean yield in the second site, implying that the CV-yield correlation might be not biologically meaningful. Conversion of the variance to remove its dependence on the mean did not validate the CV-yield negative relationship, meaning that caution is needed when interpreting the CV as a stability index for intra-crop variation. Whether the determinant factor of invalidity of TPL was the extensive intra-crop variation in the lower yielding second site can be assessed in future research.     

Collecting and Using Autobiographical Memories in Rural Social Research: A Step-by-Step Guide

Human autobiographical memory, containing information on the self and its sociocultural surroundings, is a unique reservoir of knowledge, valuable in rural social research as well as in several other fields of study. However, the use of autobiographical memories as a source of retrospective information in (rural) social research remains largely underappreciated. This article introduces a five-step guide for designing and implementing research based on individuals’ cued autobiographical memories. The article also briefly outlines some major phenomena associated with human autobiographical memory (reminiscence bump, mood-incongruency, overgeneral memory, telescoping effect) and explains how they can affect a study based on participants’ autobiographical memories.     

Of Mice and Men: When Face-to-Face Agricultural Information is Replaced by a Mouse Click

In this article we present and discuss two experiments designed to test the effectiveness of the Internet as a tool of agricultural information. Subjects were cotton producers from Thessaly, Greece. Findings suggest that, in the early stages of an innovation diffusion process, the Internet is more effective than social sources (Experiment 1). However, when urgent situations that force quick decisions occur (Experiment 2), the Internet is significantly less effective than face-to-face communication channels. In both cases, farmers who used the Internet spent more time and devoted extra effort. The experiments proved that agronomists remain the most effective information source. Results also illustrate that Internet adoption is not necessarily synonymous with its use.     

Study of variegated and white flower petals of Capparis spinosa expanded at dusk in arid landscapes

In this study,we provide the first evidence of two pairs of petals of the rapidly expanded and short-lived nocturnal flowers of Capparis spinosa L.(caper)during the prolonged drought period in Eastern Mediterranean region.The corolla of the winter-deciduous,perennial C.spinosa consists of two pairs of petals:a pair of white distinct petals and a pair of connate variegated petals with green basal parts.The results indicated the presence of substantially different amounts of chlorophyll in the two pairs of petals,while their carbohydrates’content is comparable with that of the green sepals.High resolution imaging of petal surfaces of short-lived flowers of C.spinosa, obtained by using scanning electron microscopy,revealed stomata on the adaxial epidermis on both the white and the green parts of the variegated petals;while dense hairs were found on the surface of the abaxial green parts of the variegated petals.Adaxial,epidermal cells of the variegated petals,viewed using atomic force microscopy,possess a submicron,cuticular microfolding that differs between the white and the green parts of the petals.It appears that microridges on the adaxial,white parts of petals of C.spinosa compensate for an increase in cell surface area of the short lived petals,while the roughness of the green parts of petals was found to be higher than that of the white parts.Thus,the micromorphology of surfaces of epidermal cells is expected to affect optical properties and wettability of the floral tissues.These findings may be particularly important for understanding the performance of the short-lived petals of C.spinosa,which are exposed to dryland environments.     

THE 4C APPROACH AS A WAY TO UNDERSTAND SPECIES INTERACTIONS DETERMINING INTERCROPPING PRODUCTIVITY

● The 4C approach considers intercropping performances as the result of joint 4C effects. ● Partial land equivalent ratios indicate which effect(s) are the major one(s). ● A major effect of complementarity is related to a better capture of abiotic resources. Modern agriculture needs to develop transition pathways toward agroecological, resilient and sustainable farming systems. One key pathway for such agroecological intensification is the diversification of cropping systems using intercropping and notably cereal-grain legume mixtures. Such mixtures or intercrops have the potential to increase and stabilize yields and improve cereal grain protein concentration in comparison to sole crops. Species mixtures are complex and the 4C approach is both a pedagogical and scientific way to represent the combination of four joint effects of Competition, Complementarity, Cooperation, and Compensation as processes or effects occurring simultaneously and dynamically between species over the whole cropping cycle. Competition is when plants have fairly similar requirements for abiotic resources in space and time, the result of all processes that occur when one species has a greater ability to use limiting resources (e.g., nutrients, water, space, light) than others. Complementarity is when plants grown together have different requirements for abiotic resources in space, time or form. Cooperation is when the modification of the environment by one species is beneficial to the other(s). Compensation is when the failure of one species is compensated by the other(s) because they differ in their sensitivity to abiotic stress. The 4C approach allows to assess the performance of arable intercropping versus classical sole cropping through understanding the use of abiotic resources.     

Hybridization between cotton and Malvaceae species as a tool for production of partial interspecific aneuploid cotton plants

Cotton although is an autogamous species could be cross pollinated under favorable climate conditions and/or in the presence of pollinators. The coexistence of cotton with Malvaceae species raises questions on the possibility pollen to be exchanged among Malvaceae species and on the resulted consequences. The present work was undertaken to evaluate the in situ response of cotton flowers (G.hirsutum L, G. barbadense L.) and their F₁ interspecific hybrids when are artificially pollinated with Malva sylvestris L., Hibiscus syriacus L. and Abelmoschus esculentus Moench. Furthermore, an in vitro protocol was attempted to support embryos’ growth in order to produce viable progenies originating from crosses between cotton and the aforementioned Malvaceae species. The obtained results gave evidence that pollen from the above Malvaceae species stimulated cotton ovaries without successful hybridization. The interaction between pollen and cotton’s stigmas was higher at early stages when M. sylvestris was used as pollinator but in crosses with H. syriacus and A. esculentus more ovules were activated as revealed by the percentage of carpodesis and life-time of bolls onto maternal plants. Only crosses between cotton with okra produced cotton seeds under in situ conditions. The in vitro embryo-ovule culture protocol, used, increased the number of regenerated cotton plants, especially in crosses among F₁ interspecific cotton hybrids and A. esculentus. In this case, regenerated plants were recombinant aneuploids, combining traits from both cotton species. This novel cotton germplasm possessing unique chromosome rearrangements, at aneuploid level could be proved useful after cytogenetic, molecular or QTL genetic analysis referring to important agronomic traits.     

Promoting Lifelong Learning and Satisfying Farmers' Social and Psychological Needs Through Farmer Field Schools: Views From Rural Greece

Farmer field schools (FFS) represent an alternative lifelong learning approach aimed at enhancing farmers' competences and skills through nonformal education. In this study we examined if farmers' participation in FFS is motivated by their social-psychological needs and whether these needs can be fulfilled through participation in FFS. Findings revealed that the possibility to participate in FFS is higher for farmers who experience lower levels of closeness and connectedness with their community peers and for those who score low on belongingness satisfaction. Furthermore, our analysis confirmed that FFS attendance increases felt community acceptance and facilitates the satisfaction of the belongingness need.