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Abstract The present study was conducted during two consecutive seasons 1987 and 1988 at the nursery of the Faculty of Agriculture , Moshtohor . Kalubia Governorate. This investigation aimed to study the following :- 1- The possibility of reducing the dominant habit and downward direction of tap root of pecan seedlings in favor of increasing root branching and better root distribution in the soil. 2- Enhancing thc rate of vcgctative growth in the nursery to shorten the period required to produce a nursery tree. 3- Encouraging the branching of tree top in favor of forming a more compact tree form. Therefore , the fonowing five experiments were included in the study : Experiment I: Effect of growth regulator sprays on growth 01 pecan seedUngs. Two _ year _ old pecan seedlings were transplanted in early February of both seasons. These seedlings were sprayed three times Le, May, June and July. The growth regulators used were 50 ppm TIBA, 500 ppm 6-furfuryl amino purine, 1000 and 2000 ppm SADH in both seasons. Beside, 1000 and 2000 ppm CCC were used in the first scason only. Meanwhile, 50 ppm 6- benzyle amino purine , 100 and 200 ppm PP998 treatments were applied in the second season only. These treatments were arranged in complete randomized design. The vegetative growth measurements were done from the beginning of growth and repeated at monthly intervals till September. Other growth parameters were done ’ln mid - January. The obtained results reyealed that :- a-50 ppm TIBA treatment increased the number of lateral shoots per seedling , shoot branching angle , number of leaves per seedling , number of lateral roots , total seedling dry weight shoot and root dry weights as well as root : shoot ratio. Such treatment caused significant reduction in shoot length without any effect on root length. b - 1000 and 2000 ppm SADH treatments relatively increased number of lateral shoots and roots per seedling , total seedling dry weight , shoot and root dry weight as well as root : shoot ratio. Meanwhile , SADH treatment decreased shoot length , shoot branching BDgles and number of leaves per seedling ( especially low concentration ). c - 500 ppm 6- turturyle amino purine increased number of lateral shoots per seedling, total seedling dry weight , shoot and root dry weights as well as root : shoot ratio. Meanwhile. this treatment reduced shoot length. d _ 1000 and 2000 ppm CCC treatments increased number of lateral shoot per seedling , number of leaves per seedling ( especially at high concentration) , and number of lateral roots per seedling . e _ 100 and 200 ppm PPsas treatments ( applied in the second season only ) increased number of lateral shoots per seedling , ( mainly 200 ppm ) , shoot branching angle , number of lateral roots per seedling. total seedling dry weight. root and shoot dry weights as wen as root: shoot ratio.. Meanwhile t both concentrations of PPa;38 highly reduced shoot length especially at high concentration. Other growth parameters did not show any response to PPaea treatments. f _ 50 ppm 6- benzyle amino purine improved shoot branching angles , and root dry weight Meanwhile, this treatment failed to affect other growth parameters • when it was applied in the second season.Generally t it is safe to conclude that spraying pecan seedlings with 50 ppm TIBA was the most promising treatment in enhancing better distribution of pecan seedling growth. Experiment II: Effect of nutritional sprays on growth of pecan seedlings. In early February 1987 , 2 - year - old pecan seedlings were transplanted at nursetY rows at 50 em. apart. These seedlings were sprayed three times in May, June and July with one of the fonowing nutritional sprays :- a - Tap .ater spray ( control) b - 500 ppm Zinc sulphate c - 5000 ppm urea d - 5000 ppm pata.sium sulphate These treatments were arranged in complete randomized design with three replicates and each replicate included three seedlings. The same growth measurements of experiment (I) were done.The obtained result. could be summarized - folio•• :- I - Seedling growth: a - Both potassium sulphate and urea sprays were superior in enhancing most of the growth parameters of pecan seedlings Le. number of lateral shoots per seedling, total seedling dry weight , root and shoot dry weights as well as root: shoot ratio. Meanwhile • potassium sulphate and urea sprays effect in reducing shoot length increase could probably be due to the increase in number of lateral shoot& b _ Potassium. sulphate sprays surpassed urea sprays in improving the branching angles whUe urea sprays surpassed potassium sulphate treatment in improving stem girth. However, the remaining growth parameters were not statistically affected. e _ 500 ppm zinc sulphate sprays increased number of lateral shoots per seedling, shoot branching angle, total seedling dry weight, root dry weight and root: shoot ratio. Other growth parameters were not affected by this treatment. 2 - Leaf nutrient content: a _ Potassium sulphate sprays improved leaf K , Mg and Zn contents. b _ Zinc sulphate sprays increased leaf zinc content only. e _ Urea sprays tncreased leaf N •K , Mg and Zn contents. By analysing the results of Experiment (II) • one can generalize that 5000 ppm potassium sulphate and 5000 ppm urea were the most effective nutritional sprays in enhancing growth parameters of pecan seedlings under the experimental conditions. Experiment III: Effect of mycorrhlzae fungi on growth of pecan seedlings. In February 1987 , wooden boxes were tmed with a mixture of sand and clay at the ratio of 1 : 1. The soil was disinfected with 2 % formalin solution. The soil of the firSt group of boxes was inoculated in mid _ January with Glomus rDIflcrt1CaJPus fungi. whl1e the second one was inoculated with Glomus austral/! fungL Meanwhile, the third group of boxes was left without inoculation 8S control. Moreover •the fourth group of bos.es was filled with unsterilized soil as a general controL Seedlings with pnmed roots at 15 em. below the crown were planted in the previously prepared boxes. The treatments were arranged in complete randomized design. The obtained results reycaled that :- 8 _ Glomus IIUStrs1/! fungi proved to be more effective in improving seedling growth parameters as it greatly increased lateral shoots per seedling, number of leaves per seedling • root length • number of feeder roots per seedling. total seedling dry weight • shoot and root dIy weight& Meanwhile. it reduced the ratio of root : shoot dry weight b _ Glomus JDIICJY1CSIPU8 fungi showed to be less effective in improving seedling growth. However, it increased shoot length • root length • number of feeder roots per seedling , total seedling dry weight • shoot and root dry weights. Other growth parameters did not show any response to mycorrhlzae inoculation. c - Soil sterilization failed to improve any growth parameters of pecan seedlings. It could be concluded from Experiment (III) t that growth of pecan seedlings respond well to soil inoculation by mycorrhizae Glomus BustraJe fungi proved to be more effective than G1o.-!DUB macrt1C1l1pusin improving growth of pecan seedlings in the nursery. Experiment IV: Response 01 pecan seedlings to soil treatment witb some cbemtcals. In February 1987 t wooden boxes. 100 X 75 X 50 em. ( length , width’ height) were filled with a mixture of sand and clay at the ratio of 1 : 1. The soU was subjected to the following treatments :- a - Silver nitrate was applied at the rate of OJJ7 moles I m2 surface area t above the base of the box by 5 em. t then the boxes were completed with the soiL b - Zinc sulphate was applied at the rate of 2.0 moles , m2 surface area t above the base of the box by 5 em. • then the boxes were completed with the soiL c - SollJeft without any chemical treatment as a control 1 - year - old pecan seedlings with pruned roots at 15 em. below the crown were transplanted in the previously prepared boxes. The treatments were arranged in complete randomized design. The obtained results revealed that : Silver nitrate and zinc sulphate treatments at the concentrations used in this experiment failed to exert a root pnming effect on pecan seedlings. However they affected seedling growth parameters as they increased number of leaves per seedling and total seedling dry weight only. Moreover. zinc sulphate treatment increased root length and root dry weight Evaluating results of experiment (IV)• it is easy to say that sUver nitrate and zinc sulphate treatments improved some growth parameters of pecan seedlings. However. these treatments failed • at the concentrations applied • to exert the expected root pruning effect by killing the root tip at a certain depth. Experiment V: Response of pecan seedlings to some root treatments. In both 1987 and 1988 seasons , 1 - year - old pecan seedlings were root pruned at 15 em. below the crown • then , they received one of the fonowing treatments :- a - Planting directly without treatment ( control ). b - Wounding the base of the seedling roots by applying two opposite cuts ( 2 em length ). c _ Wounding and dipping seedling roots in 1000 and 2000 ppm Indole butyric acid ( lBA ). d _ Wounding and dipping seedling roots in 500 and 1000 ppm Naphthalene Acetic Acid ( NAA ). e _ Wounding and dipping seedling roots in 600 ppm Benomyle. !_ Wounding and dipping seedling roots in 1000 ppm lBA + eoo ppm Benomyl. g _ Wounding and dipping seedling roots in 500 ppm NAA+ 600 ppm Benomyt h _Wounding and dipping seedling roots in 1000 ppm IBA + 500 ppm NAA+ 600 ppm Benomyl These treatments were arranged in complete randomized design. The obtained results could be summarized as follows :- a _ Root shortening + wounding increased number of leaves and number of lateral roots per seedling and total seedling dry weight. Meanwhile • it reduced root length and root: shoot ratio. b _ Root shortening + wounding + 1000 or 2000 ppm IBA treatments were morc cffcctivc as they increascd numbcr of leaves and number of lateral roots per seedling , root length • total seedling dry weight • shoot and root dry weights. Meanwhile. shoot length was re4lJced when 1000 ppm IBA W8B used. Anyhow. the high the lBA concentration. the more was improving effect on seedling growth. c _ ( Root shortening + wounding + 600 ppm Benomyl + 1000 ppm lBA ) • ( root shortening + wounding + 600 ppm Benomyl + 500 ppm NAA) , and ( root shortening + wounding + 600 Benomyl + 1000 lBA + 500 ppm NAA ) treatments increased number ot leaves and number of lateral roots per seedling , total seedling dry weight , shoot and root dry weights. The last mentioned treatment exerted more effect than the others. from Experiment (V)• one can conclude that root shortening + wounding + dipping in 2000 ppm lBA solution is the most promising root treatment In improving growth ot one - year- old pecan seedlings. |