الفهرس 
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Abstract
The present investigations were carried out in the Floriculture Experimental Farm, Faculty of Agriculture, Assiut University during three successive seasons 2013/2014, 2014/2015 and 2015/2016. Two experiments were done each involved in four species of rare ornamental trees; Ehretia anacua, Kigelia pinnata, Manilkara hexandra and Putranjiva roxburghii.
1st experiment ”Seed Dormancy-Breaking Treatments”
This study was conducted on influences of pre-sowing treatments of growth promoting substances combined with different sowing dates to overcome dormancy of seeds and to improve seedlings growth of tree species tested. Seeds were collected in med-July 2013 and 2014 and preserved room temperature until sowing. The seeds were sown at three dates; in September (2-month after collection), in February (7-month after collection) and in June (11-month after collection). Seeds of each species were pre-soaked in solutions of GA3, IAA, IBA and NAA, each at 250, 500 and 1000 ppm for 24 hours, besides control treatments (distilled water) every sowing date.
All pre-treated seeds were sown on moist filter papers in Petri dishes under laboratory conditions at room temperature to recorder seed measurements. After full germination of seeds, the seedlings were transplanted singly in pots filled with clay soil to study growth characteristics of the newly plants (12-month after sowing date). The interaction effects among the different treatments on germination measurements and biochemical compounds in germinating seeds were studied.
2nd experiment ”Rooting Ability of Cuttings:
The objective of this study was to verify rooting ability responses of the four tree species cuttings to auxins applications of IAA, IBA and NAA, each at 250, 500 and 1000 ppm, besides untreated cuttings. Stem cuttings were taken in two selected propagation times; March (early-spring) and September (early-autumn). After soaking cuttings of each species in growth regulator solutions individually for 24 hours for each cutting date, they planted in pots filled with peat moss. The pots were placed under shaded polyhouse conditions till the emergence of roots on cuttings.
The interaction influences among growth regulators treatments and cutting dates on root formation and root growth characteristics of the newly generated plants were studied. Transverse sections in rooting zone of cuttings were taken to verify rooting performance, initiation and development. The carbohydrate-nitrogen (C/N ratio), total phenolic compounds, rooting-promoters and rooting-inhibitors contents were determined in cutting tissues.
Each experiment was arranged in a split-plot design; the growth regulator treatments were distributed in the main-plots and cutting dates in the sub-plots. Each treatment was replicated four times that for all species tested and propagation times.
The following results obtained:
1st experiment
– All growth regulators treatment used significantly increased over controls the most seed measurements; germination percentage, mean daily germination, coefficient of velocity of germination, germination rate index and germination value of all seed species tested; Ehretia anacua, Kigelia pinnata, Manilkara hexandra, and Putranjiva roxburghii.
– Seed responses were markedly varied depending on growth regulator type and its concentration. In general, GA3 treatments were the most effective followed by IBA, IAA and NAA treatments. In relation to the concentration, pre-soaked seeds of K. pinnata and P. roxburghii in GA3 at 500 ppm solution, E. anacua in GA3 at 1000 ppm and M. hexandra in IBA at 250 ppm showed stimulatory effect on germination of these species resulting in the highest significant increases in seed measure-ments, also these seeds required the shortest time to germinate.
– The next best treatments were observed in soaking E. anacua seeds in 500 ppm IAA, M. hexandra in 500 ppm IBA or 1000 ppm GA3, and K. pinnata and P. roxburghii in 500 ppm IBA.
– Naphthalene acetic acid (NAA) at a concentration of 500 ppm was more effective in increasing germination attributes than 250 and 1000 ppm which appeared the minimum seed measurements, also these seeds required the longest time to germinate.
– Seed measurements were closely affected by sowing dates (seed storage) in September (early-autumn), in February (late-winter) and June (early-summer), seeds were stored at 2, 7 and 11 months, respectively. Pre-sowing K. pinnata in September, E. anacua and P. roxburghii in February, and M. hexandra in June were the most effective sowing dates in stimulating seed measurements, also these seeds required the shortest time to germinate every propagation date.
– Delaying the sowing date (June) for E. anacua, K. pinnata and P. roxburghii, also pre-sowing M. hexandra in the middle date (February) caused a marked decrease in germination attributes, also these seeds required longer time to germinate than other sowing dates.
– Growth regulators treatment showed significant increases in growth characteristics; shoot length, stem diameter, leaf number and area, dry weight of shoots and roots, shoot-root ratio, daily relative growth rate and vigour index of seedlings compared to untreated seeds. A positive relationship between the best vegetative and root growth, and the maximum values of seed measurements obtained from different treatments was found. Also a correlation between the minimum values of germination attributes and the worst growth was observed.
– In general, there was apparent direct relationship between the germination capacity, seed storage (sowing date) and biochemical compounds content in germinating seeds. Early sowing date in September (2-month after collection) was suitable to germinate K. pinnata, middle sowing date in February (7-month after collection) to germinate E. anacua and P. roxburghii, and the late sowing date in June (11-month after collection) to germinate M. hexandra resulting in the highest seed measurements that was closely correlated with significant increases in seed-promoting compounds of total carbohydrates, total protein, carbohydrate-protein ratio, endogenous GA-like substances and -amylase activity. In contrast, these increases were associated with seed-inhibiting compounds of ABA, phenolics and peroxidase activity.
– Delay the sowing date from September to June (11-month storage) to germinate E. anacua, K. pinnata and P. roxburghii seeds appeared a great reduction in germination attributes that was accompanied by large amounts of seed inhibitors and small quantities of seed promoters in germinating seeds.
– The results indicated that seeds of K. pinnata can be recommended to sow seeds within two months from collection, as well as E. anacua and P. roxburghii could be stored for long durations from collection, not exceeding seven months, after these periods of storage the seeds lose rapidly their germination capacity. Since seeds of M. hexandra could be stored for eleven months without losing their germination capacity.
The interaction effects between growth regulators and sowing dates cleared that the most effective combinations in increasing germination percentage, and stimulating seed viability and quality which were apparently associated with higher concentrations of endogenous seed-promoters substances, improvement of vegetative and root characteristics, as well as seedlings quality and could be recommended to apply these treatments successfully to incrase germination percentages in the four rare species tested to commercial production were obtained from the following combined treatments:
• Kigelia pinnata; GA3 at 500 ppm combined with September sowing.
• Putranjiva roxburghii; GA3 at 500 ppm combined with February sowing.
• Ehretia anacua; GA3 at 1000 ppm combined with February sowing.
• Manilkara hexandra; IBA at 250 ppm combined with June sowing.
These combinations achieved 84, 85, 87 and 82%, whereas controls recorded 32, 29, 23 and 19%, respectively.
2nd experiment
– IBA-treated cuttings with 500 ppm showed stimulatory effect on adventitious root formation resulting in the highest significant increase in rooting percentages of E. anacua and M. hexandra cuttings (51 and 28%, respectively) compared to rest of the treatments.
– NAA-treated cuttings with 250 ppm gave the highest rooting percentage in K. pinnata cuttings (56%), while rooting of P. roxburghii cuttings was dropped to zero, and did not show any response to growth regulators treatment or cutting dates.
– March (early-spring) was the optimum time for taking the cuttings of E. anacua, K,. pinnata and M. hexandra as recorded higher rooting percentages were 51, 40, 13% than those taken in September (early-autumn); 10, 16 and 8%, respectively.
– The interaction effects among treatments cleared that E. anacua and M. hexandra cuttings taken in March and treated with IBA at 500 ppm were the most effective combinations in increasing rooting percentages; 82 and 34%, respectively. Whilst, K. pinnta cuttings taken in March and treated with NAA at 250 ppm achieved the maximum rooting percentage (82%).
– A logical relationship between the best rooting percentages were obtained from cuttings of the four species tested and their great improvement of root growth and development that declared significant increases in root characteristics; root number per cutting, root length, and fresh and dry weight of roots.
– The highest rooting ability of cuttings tested was closely correlated with the maximum contents of carbohydrate-nitrogen (C/N ratio) and root-promoting substances (auxin) in their tissues, also a great reduction in root-inhibitors concentration (ABA, GA and phenolics) was found.
– The anatomical structure in stem cutting bases indicated that they are generally more difficult-to-root that relate to presence of sclerenchyma ring between phloem and cortex that is acted as mechanical barriers preventing root emergence. Cuttings of E. anacua and M. hexnadra treated with IBA at 500 ppm, also K. pinnata treated with NAA at 250 ppm stimulated cell division and rooting processes led to the sclerenchymatic tissues more incoherent, the developed root primordia are penetrated through weak gaps that would permit root emergence, this is obvious in the superior rooting of these treatments. In P. roxburghii cuttings, the sclerenchyma ring has a greater degree of sclerification of tissue form a continuous hard ring which prevent the emergence of the root primordia from the cuttings. Auxin treatment unable to separate slcerenchyma cells, so the cuttings failed to root. It is found a direct relationship between the density or continuity of sclerenchyma cells and rooting potential in woody stem cuttings.
– It could be recommended to propagate;
• Ehretia anacua by seeds in February after treating with GA3 at 1000 ppm (87%), also by cuttings with IBA at 500 ppm in March (82%).
• Kigelia pinnata by seeds in September with GA3 at 500 ppm (84%), also by cuttings with NAA at 250 ppm in March (82%).
• Manilkara hexandra by seeds in June with IBA at 250 ppm (82%), also by cuttings with IBA at 500 ppm in March (34%).
• Putranjiva roxburghii by seeds only in February with GA3 at 500 ppm (85%).