Geranium dissectum

Abstract: Geranium section Dissecta, (Geraniaceae) consists of four species in the world. It is believed that the center of diversification of this section is Eurasia. G. dissectum is the only species of this section in northern parts of Iran. A multivariate morphometric study showed that some quantitative characters such as deeply divided leaves, shorter and narrower petals, and shorter filaments are main diagnostic features of G. dissectum. This tannin-rich plant has many uses in folk medicine. There is no information on its population genetic structure, genetic diversity, and morphological variability in Iran. Due to the medicinal and weed importance of this species, a genetic variability and populations’ structure study is performed studying 21 geographical populations of G. dissectum. Perhaps the most important biological challenge today is the conservation of biodiversity. Populations were studied from morphological and genetic (ISSR) points of views. Both intra and inter-population morphological and genetic variability was observed in the studied accessions. ANOVA and CVA tests revealed significant morphological difference among populations. Similarly, AMOVA and Hickory tests revealed significant molecular difference among geographical populations. Mantel test produced significant positive correlation between genetic and geographical distance of the studied populations. Networking, STRUCTURE analyses and population assignment test revealed some degree of gene flow among these populations. Consensus tree based on morphological and genetic data separated some of these populations from the others suggesting the existence of ecotypes within this species.

Abstract: Herbicides may drift onto road verges or natural areas adjacent to arable fields and affect nontarget plants. The effect of low doses of mecoprop-P on the competitive interactions and plant community dynamics was investigated in a model system using Capsella bursa-pastoris and Geranium dissectum as test plants. Dose–response experiments on single species showed that compared to G. dissectum, C. bursa-pastoris was more affected by mecoprop-P. Consequently, we expected that G. dissectum would outcompete C. bursa-pastoris when mecoprop-P was applied at a low dose in the competition experiment. Indeed, mecoprop-P had a significant effect on the interspecific competitive ability of both C. bursa-pastoris and G. dissectum. Our previous expectation, however, was not met: The interspecific competitive ability of both species increased significantly with the dose of the herbicide, and it was predicted that C. bursa-pastoris and G. dissectum are more likely to coexist in natural habitats with low concentrations of the herbicide compared to natural habitats with relatively high concentrations. The results from the dose–response experiments on the single species and the more laborious competition experiment approach, which is assumed to mimic the dynamics of plant communities more closely, show considerable discrepancies even though the experiments were performed at the same time and in the same greenhouse. This finding generally reduces the credibility of using single-species tests in ecological risk assessment of herbicide use.

Abstract: Heliothis virescens (F.) (Lepidoptera: Noctuidae), the tobacco budworm, is a multivoltine, polyphagous, highly mobile and economically important insect indigenous to the Americas. A majority of larvae of a given H. virescens population feed on different host plant species in different generations and different geographic locations, apparently depending largely on the local relative abundance of host plants (Table 1). In Mississippi, for example, adults eclose in May from overwintered pupae to oviposit primarily on Geranium dissectum L. and G. carolinianum L. (wild geraniums), Vicia villosa Roth, (winter vetch), and Trifolium resupinatum L. (Persian clover), as well as at least six other apparently less important species (Stadelbacher 1981, Snow and Brazzel 1965). The second through fourth generation larvae are primarily on Gossypium hirsutum L. (cotton) even though four other hosts are acceptable (Snow and Brazzel 1965). Cotton probably does not contribute as significantly as wild hosts to the fifth and final (overwintering) generation due to agricultural defoliation and tillage (Roach and Hopkins 1979; however, see also Laster and Furr 1971). In contrast, in North Carolina, Nicotiana tabacum L. (tobacco) is the major host in each generation although cotton is attacked also. Tobacco is an acceptable host in Mississippi, but very little is grown there (Snow and Brazzel 1965).

Abstract: . The effects of grazing upon the establishment, survival, growth and reproduction of a grassland annual Geranium dissectum growing in a sward dominated by grasses were examined in a replicated grazing experiment with sheep. Seeds were sown in both summer and autumn, and grazing was controlled to produce two levels of grazing in winter, two levels in spring, and two in summer, combined in a 2 x 2 x 2 factorial experimental design. Higher intensities of grazing in the period immediately before emergence benefitted plant establishment, but subsequent survival showed many interactions between factors, demonstrating that under certain conditions and at certain times grazing was detrimental. It is suggested that the frequency of G. dissectum in the grassland was low because the heavy grazing conditions that foster seedling emergence also jeopardize subsequent survival. This may also be why productive grassland communities in general contain few palatable dicots.