Forced Flowering in Mandarin Trees under Phytotron Conditions

Phytotron has been widely used to assess the effect of numerous parameters on the development of many species. However, less information is available on ...

Universitat Politècnica de València

Information about fractal dimension is collected so that it can be applied to time series interpreting Hurst coefficient. The population size of a species is modelled as a dynamic system. The Hurst coefficient is calculated for these times series. A computer programme has been elaborated to compute the Hurst exponent of time series using the algorithms of range increment, second order moment increment and local second order moment increment. It has been applied to time series of birds' populations.

Fractal dimension of birds population sizes time series.

An iterative model is developed to evaluate the reproductive strategies of plants in environments with different frequencies and intensities of disturbance. Two extreme reproductive strategies are compared: the "homocarpic" strategy, in which all the seeds germinate the following spring, without dormancy, and the "heterocarpic" strategy, whereby, each year, half of the existing seeds germinate. It is observed that this sort of heterocarpy is beneficial in environments with strong perturbations, in which a high percentage of the population dies. However, the frequency of such perturbations does not cause changes in the advantage of one strategy over the other. The results suggest that the intensity of the disturbance is much more important than the frequency.

The importance of the intensity and frequency of perturbations on the germination delay.

Hybridization between tetraploids and their related diploids is generally unsuccessful in Centaurea, hence natural formation of triploid hybrids is rare. In contrast, the diploid Centaurea aspera and the allotetraploid C. seridis coexist in several contact zones where a high frequency of triploid hybrids is found. We analyzed the floral biology of the three taxa to identify reproductive isolation mechanisms that allow their coexistence. Flowering phenology was recorded, and controlled pollinations within and between the three taxa were performed in the field. Ploidy level and germination of progeny were also assessed. There was a 50% flowering overlap which indicated a phenological shift. Diploids were strictly allogamous and did not display mentor effects, while tetraploids were found to be highly autogamous. This breakdown of self-incompatibility by polyploids is first described in Centaurea. The asymmetrical formation of the hybrid was also found: all the triploid intact cypselae came from the diploid mothers pollinated by the pollen of tetraploids. Pollen and eggs from triploids were totally sterile, acting as a strong triploid block. These prezygotic isolation mechanisms ensured higher assortative mating in tetraploids than in diploids, improving their persistence in the contact zones. However these mechanisms can also be the cause of the low genetic diversity and high genetic structure observed in C. seridis. 

Allogamy-Autogamy Switch Enhance Assortative Mating in the Allotetraploid Centaurea seridis L. Coexisting with the Diploid Centaurea aspera L. and Triggers the Asymmetrical Formation of Triploid Hybrids.

Organic agriculture is becoming increasingly important, and many natural products are now available for organic farmers to manage and improve their crops. Several ethnobotanical studies have indicated that the use of nettle slurry as fertilizer in organic farming for horticultural crops is spreading. Sometimes, however, the consequences of using these natural products have been poorly evaluated, and there is very little scientific evidence for the effects of using these slurries. In this study, we aimed to analyze the possible effect of nettle slurry on potato yields produced by organic farming. To achieve this main objective, we assessed the effect of nettle slurry on potato yields, plant size and growth parameters, chlorophyll content, and the presence of pests and diseases. Different slurry doses were assessed in 36 plots and nine variables were measured during the crop cycle. Under these field experimental conditions, nettle slurry (including one treatment with  in combination with ) had no significant effects on yield, chlorophyll content, or the presence of pests and diseases in organic potato crops. The highest chlorophyll content was found in the double dose treatment, but the difference was not significant. This result, together with a small improvement in plant height with the double dose treatment, might indicate very slight crop enhancement which, under our experimental conditions, was not enough to improve yield. The  and  slurry chemical analyses showed very low levels of nitrogen, phosphorus, and potassium.

Effects of nettle slurry ( L.) used as foliar fertilizer on potato ( L.) yield and plant growth.

Although polyploidy is considered a ubiquitous process in plants, the establishment of new polyploid species may be hindered by ecological competition with parental diploid taxa. In such cases, the adaptive processes that result in the ecological divergence of diploids and polyploids can lead to their co-existence. In contrast, non-adaptive processes can lead to the co-existence of diploids and polyploids or to differentiated distributions, particularly when the minority cytotype disadvantage effect comes into play. Although large-scale studies of cytotype distributions have been widely conducted, the segregation of sympatric cytotypes on fine scales has been poorly studied. We analysed the spatial distribution and ecological requirements of the tetraploid  and the diploid  in east Spain on a large scale, and also microspatially in contact zones where both species hybridise and give rise to sterile triploid hybrids. On the fine scale, the position of each  individual was recorded along with soil parameters, accompanying species cover and plant richness. On the east Spanish coast, a slight latitudinal gradient was found. Tetraploid  individuals were located northerly and diploid  individuals southerly. Tetraploids were found only in the habitats with strong anthropogenic disturbance. In disturbed locations with well-developed semi-fixed or fixed dunes, diploids and tetraploids could co-exist and hybridise. However, on a fine scale, although taxa were spatially segregated in contact zones, they were not ecologically differentiated. This finding suggests the existence of non-adaptive processes that have led to their co-existence. Triploid hybrids were closer to diploid allogamous mothers () than to tetraploid autogamous fathers (). This may result in a better ability to compete for space in the tetraploid minor cytotype, which might facilitate its long-term persistence.

Distribution and ecological segregation on regional and microgeographic scales of the diploid  L., the tetraploid  L., and their triploid hybrids (Compositae).

Alfonso Garmendia

Instituto Agroforestal Mediterráneo

Universitat Politècnica de València

Forced Flowering in Mandarin Trees under Phytotron Conditions

Alfonso Garmendia

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Instituto Agroforestal Mediterráneo

Universitat Politècnica de València

Forced Flowering in Mandarin Trees under Phytotron Conditions

Instituto Agroforestal Mediterráneo