Iranian Journal of Rangelands and Forests Plant Breeding and Genetic Research
Year:2006 | Volume:14 | Issue:2 (24)|Papers Count:9

In order to determine the response of 3 annual clover species (6 accessions) against water stress, a greenhouse trial was conducted in a factorial an experiment based on 3 replications CRD in 2004. Root and shoot dry weight and length and root -shoot length ratio of two species and four sub species of clover were measured under (100, 75, 50 and 25) percent of field capacity (F.C). The results showed that the highest shoot and root length were obtained by 75 and 100% (F.C) treatments with 15.24 and 14.19 cm means, respectively. Also the lowest shoot and root length was related to 25% (F.C) treatment with 5.52 and 9.71 cm means, respectively. The comparison of means in shoot and root dry weight indicated that the maximum dry weight was produced by T. alexandrinum var. carmel with 0.95 and 1.1g means, respectively. While, the lowest shoot dry weight was produced by ‘Kazeroun Baladeh’, ‘Kordestan Dochin’ and ‘Abadeh Souriun’ populations. Also the lowest root dry weight was related to the species of ‘Kordestan Dochin’ population. The results showed that as Varamin species (T. alexandrinum var. carmel and T. subterraneum var clark) were more tolerant than the others. ‘Kazeroon Baladeh’ and ‘Arak Haft chin’ from T. resupinatum were the most sensitive to drought stress. Also ‘Kordestan Dochin and ‘Abadeh Sorrian’ from T. resupinatum were introduced as semi-tolerant species.

To study the positive or negative effects of rye (Secale cereale L.) and Johnson grass (Sorghom halepens L.) allelochemicals on corn (Zea mays L.) seed germination, an experiment in Complete Randomize Design with 3 replications was conducted in laboratory condition in Tehran University. Different concentrations of rye, Johnson grass and rye + Johnson grass aqueous extracts (2.5%, 3.75% and 5%) were prepared and for control treatment, distilled water was used. The effect of treatments on percentage of germination, germination rate, mean time to full germination, seedling dry weight and length of radicle and coleoptile were measured. Results showed that high concentration of Johnson grass extract (5%) significantly decreased all measured traits, however, rye extract showed a significant decreasing effect only on germination rate and length of coleoptile in this concentration (5%). The mixture of rye and Johnson grass extracts showed a synergistic effect and caused more reduction in the higher concentration (5%) for the studied traits. But no significant differences were observed in low concentrations (2.5% and 3.75%).

Salvia nemorosa as a member of Lamiaceae, is used in food and pharmaceutical industries. Also Salvia nemorosa is an ornamental plant. In vitro culture of S. nemorosa on MS medium with different concentrations of hormones was investigated root, hypocotyls; leaf and apical meristem of sterile seedling grown on hormone free MS medium were used as explants. Leaf and apical meristem explants in MS medium containing 5mg/l NAA and 5mg/l 2ip formed the compact and green calli and then leaves and roots appeared. MS medium containing 5mg/l IBA and 5mg/l Kin was only suitable for callus induction and dedifferentiation of leaf from leaf explants .With MS medium containing 5mg/l NAA and 2mg/l 6_BAP, apical meristem formed the green calli and then leaves and shoots appeared. Subculture of samples on fresh medium resulted in plant regeneration. Thus, MS medium with NAA and 6-BAP is best medium for propagation of S. nemorosa plant than the other medium. On MS medium containing 5mg/l NAA and 5mg/l 2ip, hypocotyls formed yellow calli, but root explants showed no callus induction. On MS medium with 5mg/l IBA and 5mg/l Kin, hypocotyls and root explant formed yellow and green calli, respectively without any organogenesis or plant regeneration.

Effect of water stress on dry weight and photosynthetic pigments in two sainfoin species (Onobrychis radiata & Onobrychis viciifolia) was surveyed in a factorial experiment based on a randomized complete block design with 4 replications. The plants under study were grown in a greenhouse environment with the maximum temperature of 38oC and the minimum temperature of 14oC. Forty days after cultivation, both species were put under water deficit stress based on the subtraction farm 75% field capacity (FC) and 50% FC, and samplings were carried out in germination and growth stages, with irrigation level of 100% FC being taken as control. In both types, water deficiency tension resulted in decreased relative growth rate (RGR), leaf area ratio (LAR) and relative leaf growth rate (RLGR). The measurement of imposed tension indices showed that Onobrychis viciifolia underwent the greatest tension in such a way that this species withheld at 50% FC tension level. The ratio of root to shoot (R/S), length and weight of root increased, but in Onobrychis radiata the increase of these parameters were much higher than those of O. viciifolia. The biochemical surveys showed that carotens content and chlorophylls content decreased under the stress conditions in both species, but the xanthophyll content increases and the ratio of carotenoids to chlorophylls increased, with O. radiata being higher in this respect. Because the xanthophyll cycle is one of the strong mechanisms of anti - oxidation in plants, and prohibits of demolition of membranes and supports chlorophyll against photo – oxidation, the increase of xanthophyll results in the increase of plant’s resistance – threshold against oxidation stress arising to water deficit.

Several species of wild pear are native to Fars province in Iran, but little information about different aspects of their growth habit is available.  Investigation on breaking seed dormancy and germination is needed for propagation of wild pear species as a rootstock for common pear and for afforestation. This research was carried out to study the methods of breaking dormancy, germination and seedling growth of different genotypes of three wild pear species including: Pyrus syriaca, Pyrus glabra and a probable natural hybrid of Pyrus syriaca × Pyrus glabra.  Seeds of Pyrus glabra (genotype 11) were used for test of viability, excised embryos and chemical scarification.  Seed viability was tested using tetrazolium (1%) and results showed that seeds were 100% viable. Based on the results of excised embryo test, germination percentage of stratified excised embryos was more than that of non stratified embryos.  Chemical scarification with concentrated sulfuric acid did not affect breaking dormancy of seeds. Results of seed stratification for 0, 15, 30, 45 and 60 days indicated that 60 days stratification was the best treatment for removing dormancy in wild pear species seeds. Seeds originated from different trees (each tree considered as a genotype) of wild pear species showed different responses with regard to stratification period.  Seedling growth of Pyrus glabra was affected by stratification period and 45 days stratification was more effective on hypocotyl length and seedling fresh weight than the other treatments.  It could be concluded that stratification for 60 days was the best treatment for breaking dormancy and seed germination of wild pear species studied in this research.

Correlation between media and explants in micropropagation method in different stages of growth and absorption, transport and collection of materials are unknown. Different species of plants that grown in the same conditions differ in use of salts. The form of N uptake is also determined by plant preferences for certain N forms. The form of N uptake is also subject to plant preferences by which plants maintain their cation/anion balance during uptake. Ion equilibrium and propagation coefficient of jojoba were analyzed on the treatment media (different sources and concentrations of N compared to MS medium). The explants grown in MS medium containing 0.5 mgl-1 BA and 0.01 mg l-1 IAA for 30 days. The explants were transferred to treatment media (NH4NO3 ¸ KNO3 and KNO3 + NH4NO3). They were left under controlled environment with temperature of 25oC and day length of 18 hours. We analyzed content of N, P, K, Na, Ca, propagation coefficient and dry weight of samples. The highest content of mineral elements was in samples from media including NH4NO3 or KNO3 + NH4NO3. Contents of K and Na in samples showed no significant difference. An increase in ion content, dry weight and propagation coefficient was observed after 45 days of transplanting to the treatment media including NH4NO3.

Variation for forage production was surveyed between annual medics under various periods of irrigation. The research was carried out in a factorial experiment based on a completely randomized design with 3 replications in Zalleh Research Station, Sanandaj, Iran, 1995. Studied factors were humid with 4 levels (irrigation intervals including 5,4,3 and 2 days) and medic species with 6 levels (1-Medicago truncatula, 2- M. scutellata, 3- M .rigidula, 4- M. littoralis , 5- M. rogosa paragosa and 6- M .orbicularis). Results showed that average shoot (SW) and root (RW) shoot and root dry weight of aerial part (SW) and root part (RW) of plant were 5 and 4.7 g respectively and SW/RW ratio was about 1. Based on the analysis of covariance (number of plant in vase as covariate), humidity levels showed significant differences P<0.01 for SW and RW and the watering interval of 2 days caused the highest weight and watering interval of 5 days caused the lowest weight of SW and RW. Differences among species for SW and RW was significant P<0.01. Mean comparison (Duncans multiple range test at p£0.01) showed that M.tr., M.Sc. and M.ri. In addition for SW and RW were higher than other species. Also, interaction of humid – species for SW and RW was significant (p£0.01). This means that different species of medics showed different reaction to humid changes. M.tr. and M.ri. As 2 resistant species in all humid levels showed stability in SW and RW. M.sc. has showed high SW and RW only in high humid condition. RW showed and significant (p£0.01) positive correlation (r=0.91) with SW and so regression coefficient (b) RW on SW was significant (p£0.01) and determination coefficient (R²=%98) was very high.