جستجوی مقالات مرتبط با کلیدواژه "گندمیان" در نشریات گروه "مکانیزاسیون کشاورزی"

Bromus danthoniae Trin. is an annual grass species which grows mainly on dry grassy rocky mountain slopes and grassy steppe, and is grazed by many herbivores and recognized as a useful pasture plant. The chromosome number, morphological and anatomical traits of 82 genotypes of B. danthoniae belonging to three sub-taxa were investigated. Twenty-seven quantitative and 20 qualitative morphological traits were evaluated. The results of analysis of variance showed that B. danthoniae genotypes varied significantly for all quantitatively tested traits. Based on cluster analysis, the genotypes were divided into four groups which mostly corresponded to their subspecies identities. According to correlation analysis, lemma length had strong positive correlations with other traits such as awn length (r=0.55**), lemma width (r=0.72**) and caryopsis length (r=0.84**). In addition, lemma width was significantly correlated with the traits like floret number per spikelet (r=0.47**) and caryopsis length (r=0.58**). Based on factor analysis, the first three factors encompass about 51% of total variation. Overall, lemma length and lemma width were the two reliable traits for morphological investigations in this species. The results of chromosome counting showed that B. danthoniae subsp. danthoniae and B. danthoniae var.lanuginusos Roshev. were diploid (2n=2x=14) whereas B. danthoniae subsp. pseudodanthoniae (Drobov) H. Scholz was tetraploid (2n=4x=28). The results of leaf surface anatomy showed that tetraploid genotypes had larger stomata but lower stomatal density than the diploid ones, thus a comprehensive relationship between genome size and guard cell size cannot be ruled out as a plausible explanation for differentiating the ploidy levels. The high morphological variations among the B. danthoniae genotypes explain the habitat distribution of this species and enable us to incorporate this knowledge into practice by exploiting the variation for improvement of pasture production.

There are various methods for measuring the utilization of grasses that each of these methods has its advantages and disadvantages. Using gauge for measuring exploitation and utilization of grass and grass-like species is one of these methods. This study introduces the utilization scale to determine the utilization rate of three species of grasses. Thus، the utilization rates of three species of grasses (Agropyron elongatum (Host) P. Beauv. Agropyron pectinofome (Roemen & Schutes.) and Hordeum bulbosum (L.)) were determined using gauge utilization. In order to use a utilization gauge the existence of utilization scale for studied species is necessary while such scale has not already been prepared in our country therefore at first the scales must be developed. Thus 10 specimens of the studied species were sampled to be used for preparing the utilization scale. Results showed that all regression equations have a high correlation coefficient and were all significant and functions were as natural logarithm or Napery which means the relationship between height and weight is affected by canopy structure of the species. The results of the utilization scale showed that with a specified level of utilization، remained height percentage of Hordeum bulbosum (L.) species is less than Agropyron elongatum ((Host) P. Beauv.) and Agropyron pectiniforme (Roemen & Schutes.) species. This seems to be related to the plant structure of Agropyron elongatum ((Host) P. Beauv) and Agropyron pectiniforme (Roemen&Schutes.) species that these species form bunch grass in which weight of plant is mostly concentrated on the upper parts of the plant. Because this method is rapid، nondestructive and very cheap، the use of gauges is recommended to estimate the utilization rate of grasses species native to Iran.