Summary of some germination studies in the Division of Forest Investigation, Bureau of Forestry College, Laguna

Media

Part of Forestry Leaves

Title: Summary of some germination studies in the Division of Forest Investigation, Bureau of Forestry College, Laguna
Language: English
Rights
Fulltext: Summarg of Some Germination Studies in the Division of Forest Investigation, Bureau of Forestrg College, Laguna* By DOMINGO v. jACALNE Acting Silviculturist Bureau of Forestry INTRODUCTION One of the most difficult problems that constantly confront nurserymen in our reforestation projects is successful seed germination. Very often, these men complain of their repeated failures and of the poor germination results obtained in their nurseries. This may be due to the lack of definite knowledge regarding the proper care and methods of germinating seed, particularly the behavior of seeds, the proper treatment to be used and other factors. Despite the meager knowledge of the * Read before the Eighth Pacific Science Congress, University of the Philippines, Diliman, Quezon City, on November 24, 1953. ,----- - - -------·--------! I I Compliments ol Luis Pareja DEALER IN LOGS Caliraya, Lumban, Laguna Compliments ol Erickson Lumber Co. Mati, Davao VICTOR L. ERICKSON Proprietor l'!I M anaaer GRADUATION ISSUE, 1957 behavior and requirements for successful germination of the seeds of our various and important tree species, only a few investigations along this line have been conducted. Besides, the few enlightening and useful results of published completed studies arc scattered, thUs they are overlooked by nurserymen, officers-in-charge of reforestation projects and by others interested in such data. Hence, for the interest and benefit of these men, the writer compiled the results of previous and present studies in the form of a summary wherein the methods or techniques employed by the individual researchers are incorporated. DISCUSSION OF RESULTS OBTAINED BY VARIOUS WORKERS Seed storage.-All seeds that are not sown immediately after collecting and cleaning are stored carefully in order to keep -:ir prolong their viability untiL....such time as they are needed to be sown in the nursery .>r directly in the field. How long the seeds will stay viable, however, depends on a iarge degree upon the manner of storage used and on keeping to the minimum the adverse factors affecting viability. The methods used and the results of E·xperiments conducted by Lopez (9) on mahogany (Swietenia macrophyila King) and Acuiia ( 1) on West Indian Cedar (Cedrela odorata Linn.), are presented in the following tables: Page 11 Length of viability of the seeds of Mahogany (Swietenia macrophylla King) stored under various media. Method of storage Length of storage No. of days Gennination per cent Fruits stored in closed cans with powdered charcoal and buried 40 cm. deep in the ground under shade ................ . 132 72 Seeds stored in closed cans with powdered charcoal aAd buried 40 cm. deep in the ground under shade . . . . . . . . . . . . . . . . . . . . . . . . 132 132 70 4 Control seeds stored in cans without charcoal Storing the seeds in closed cans with powdered charcoal .......................... . 132 30 Seeds stored with powdered charcoal in glass jars sealed with paraffin ............ . 101 30 6 Seeds stored with powdered charcoal in closed paper envelopes .................... . 101 Effect of storage in paraffin sealed bottles on the germination of West Indian Ceqar ( Cedre/a odorata Linn.) seeds.* Length of storage (in days) Germination per cent 35 90 63 80 91 60 112 2-40 147 No germination * Germination media: Fine sand in seed flats. Considering the ease, practicability and economy in labor and material, the former researcher recommended that seeds of mahogany be stored in closed cans with powdered charcoal and buried 40 centimeters deep in the ground in the shade after the fruits are gathered. To obtain satisfactory results, the seeds of this species should not be kept under such kind of storage more than 120 days. The second table shows that the seeds of West Indian Cedar could be kept in paraffin sealed bottles up to 91 <lays without very much loss of viability, during which time, it is still possible to get over 60 per cent germination. The author also found that the germinative energy of the species is greatest within 21 days from the date of -sowing. Germination media.-The choice of the most suitable medium for germination and !or raising planting stocks of any species of seeds is often difficult. For most species, however, the soil is the most satisfactory because it is the natural medium. Also it gives the most uniform results especially i.n extensive scale. Caguioa ( 3) made a study on white !auan (Pentacme contorts (Vid) Merr. & Rolfe) seeds. The various media used in his experiment consisted of clayloam (control), sawdust-clay loam mixture, 1: 1 by volume; charcoal-clayloam mixture, 1: 1 by volume; ash-clay loam admixture of 1: 2 by volume; pure fine sand, sawdust and charcoal. On the basis of germination per cent, the results obtained were as follows: sawdust, 95.01 % in a period of 14 days; ashdayloam, 94% in 10 days; sawdust-clay!oam, 92 % in 12 days; clayloam, 89.75% in 16 days; charcoal-clayloam, 86.8% in 14 days; charcoal, 86.4'/o in 14 days and sand, 76'/o in 8 days period. From the standpoint of mortality and of producing the greatest number of vigorous and healthy seedlings, the order of suitability of the said media are as follows: clayloam, sawdust-clay loam, sand, charcoalclayloam, ash-clayloam, sawdust, and charcoal. This study reveals that the above ma1erials and mixtures as germination media FORESTRY LEAVES give satisfactory results and that the seeds of white lauan germinate very rapidly, the period of germination being from 2 to 16 days. While sawdust gave the highest percentage of germination, it did not prove to be a good type of surface soil for growing planting stocks and the mortality is high. Such is also the case with the ash-clayloam mixture. Sawdust-clayloam mixture is a good type of surface soil medium next to clayloam, as judged from the bases mentioned above. Sand was found to be a very poor germinating medium and a poor surface soil for such species. Charcoal is &bsolutely unfit for germinating and growing white lauan seedlings. Density of .sowing.-What is important t.o consider in the density of sowing is the amount of light and 'space requirements of the species and whether the stock will be transplanted when 1 year, 2 or 3 years old, and whether it will undergo one or more transplantings in the nursery before they are permanently set in the field. In sowing seed, therefore, the amount needed per square unit of seed bed should be carefully determined. This will depend on the characteristics of the species, the size and vigor· of the seed and the number of seedlings desired per unit of area. In computing the amount of seed to F.OW in a seedbed, Hawley ( 8) gives the following formula: where: p == A D G == s z == A X D p ==~~~~~~G XS X Z pounds of seeds area in square feet number of seedlings square foot aesired per germination per cent number of seeds per pound a variable factor expressing the difference between the germination secured m the tests and that secured in the seedbed (Olson, 1930). Studying the effects of density of sowing on the germination of seeds of Benguet Pine GRADUAnON ISSUE, 1957 ( Pinus insularis Endl. ), Defensor ( 5) found that density of sowing has no direct effect '>~ the percentage of germination; that density, however, has some direct relationship to mortality partly due to damping-off and to the fact that the seed that is not protected is eaten by ants. Depth of sowing.-Most seeds need soil covering to induce germination and to keep them from drying up through insulation. It &lso protects the seeds from birds, ants, rodents and other agencies. Although the seed is usually covered to a depth equal to its greatest diameter, some seeds germinate best when sown just a centimeter or so under the surface of the soil while others require deeper sowing. The depth of the soil cover, as found by various studies in the Division of Forest Investigation, varies with the species. A study of Quimpo ( 12) on the effects ~! depth of cover on the germination of ~.eeds of large leaf mahogany (Swietenia macrophylla King) showed that depths of 4, 6, 8, and 10 centimeters are favorable; 8 centimeters gave the highest percentage. The following table shows his findings on the effects of soil cover on the germination per cent of mahogany studied: Sowing depth 2 centimeters 4 6 8 10 surface " n " " Average germination per cent Experiment I Experiment II 27.25 58.27 ./68.26 69.75 63.38 0.10 5.75 13.00 28.39 35.38 35.50 0.90 The comparative results of the experiment of Caguioa (3) on Alupag (Euphoria didyma Blanco) is shown in the following table: Sowing depth 2 centimeters 4 " 6 " 8 ,, 10 n 15 " surface Germination per cent 46.5 57.5 60.0 56.0 33.0 27.0 7.0 Period (days) 75 80 80 90 80 85 65 Paga 13 As shown in the above table, the suitable depth of sowing alupag seeds is from 2 to 8 centimeters. The author also found that at these depths, the quality and size of planting stock produced is better than that when the seeds are sown at the surface or at 10 to 15 centimeters depths. Denoga ( 7) in connection with his studies on hastening the germination of untreated teak (Tectona ~randis, L.f.) seeds, sown in untreated soil, obtained percentage cf germination of 40% by surface sowing, 32% for 1 cenfmeter depth and 29'/c for 2 centimeters depth. He got very poor results with 3, 4, and 6 ems. depths. Seeds failed to germinate altogether beyond 6 centimeters deep. The only drawback in surface sowing is undue exposure of the seeds to ants, rodents and other pests. With regard to the seeds stored 60 days in a !:haded pit and later sowed 2 centimeters deep in untreated soil, 69% germination was obtained. Seed treatments.-Delayed germination in many forest tree seeds is due mainly to the impermeability of the seed coat which inhibits water absorption, or to a state of ciormancy inherent in the embryo itself. In1-ierent dormancy generally disappears during a rest period or an after-ripening period in which certain physical and chemical changes necessary for germination occur within the embryo. In seeds which require ::i rest period, these changes must occur either during sterage or while the seeds are in the germination bed b~fore satisfactory germination can be obtained. Tourney and Korstian ( 14) suggested the following methods of seed treatments to hasten germination: 1 . Removing the pericarp or tests in whole or in part when it is more or less impervious to moisture because of its hardness or leathery characters. 2. Softening and rendering an impervious pericarp or making testa more absorptive by the use of chemicals as sulphuric acid or potash lye. Page 14 3. Soaking in hot water, especially when the endosperm or kernel of the seed is cartilaginous in character. 4 . Storing at low temperature during the rest period to stimulate afterripening so as to overcome inherent dormancy. A number of experiments on seed treatments have been conducted in the Division of Forest Investigation ranging from soaking the seeds in tap water, scalding at certain temperatures, burning the seed with cogon grass, immersing in 36 normal sulphuric acid, cutting the ends of the seeds (nicking), mixing the seeds with wet wood ash, mulching, removing the shell, slightly cracking the shell, and using peat moss, or horse dung. Some satisfactory results were obtained and were recommended by those who made the studies. Conducting an experiment in 1936 to find the relative efficacy of some of the most common methods locally used to hasten, and to get a better percentage of germination. of akle (Albizzia acle (Blanco) Merr.), Delizo (6), us_ed the following methods: 1. Soaking the seeds in 36 normal H.SO• at varying length of time, i.e., 15 minutes, 25 minutes, and 60 minutes, respectively. 2. Soaking the seeds in tap water for two hours. 3. Cutting the ends (nicking) of the individual seeds. The results of this study showed that mechanical wounding of the seeds (nicking) induced rapid germination but the advantage was offset by the low percentage of germination because of fungus infection. The most effective of the treatment used is immersion in concentrated sulphuric acid for one hour. The acid partly dissolved the cutin and thus allowed a more rapid imbibition of water by the seed. The normal germination period of akle seeds without treatment is 120 days. The comparative results of the various treatments are shown in the following table: FORESTRY LEAVES - - - - .... - 0 ....... t...;. - - - . ... A .. . - BITAOG SEEDS Plate 1.-Seeds and Cross Section of Bitaog and Lumbang Seeds. AKLE SEEDS Plate 2.-Wbole Seeds and Cross Section of Pili and Akle Seeds. Plate 3.-Whole Seeda and Croa1 Section of Mahogany and Teak Seeda. Plate 4.-Mahogany Fruits. Nwnber of days required to start and complete germination TREATMENT No. of days to start germination No. of days to complete germination 1. Soaking the seeds in H2SO•, 1 hr. 2 . Ends of seeds cut 9 9 10-112 10-112 20-112 22 27 23-112 35 48-112 3. Soaking in ff.SO•, 25 min. 4. Soaking in H2SO•, 15 min. 5 . Two hours in tap water 6. Untreated seeds (control) Paras ( 11) who made a study also on hastening the germination of bitaog (Calophyllum inophyllum Linn.) seeds which without any treatment normally takes about 120 119 two months to complete germination is fihown in the following table; the results of three trials of different treatments: Nwnber of days required by the seeds to start and complete germination Treatment I i'IRST TEST ISECONDTESTITHIRD TEST I Begin- \ Fin- Begin- \ Fin- BeginI Finl ning * ish * ning ish ning ish AVERAGE Days Control 48 Cracked .......... 48 With cogon mulch 62 Shell removed 23 100 112 86 25 67 32 45 18 33 60 47 49 57 34 25 25 39 42 57.33 38.00 53.50 22.00 52.66 70.33 66.50 38.66 * Beginning: Number of days to start genninat:iDn. * Finish Germination completed after 1st germination. The complete shelling of bitaog seeds hastens the start of germination to only 22 days from 57 days in the case of those planted unshelled. The duration is shortened from 52.66 in the case of untreated to 38. 66 and the percentage of germination inrreased from 63.00 to 93.10 per cent. Apparently this shows that the chief cause of delay in starting germination was the hardness of the shell or seed coat. Partial c.r complete removal of the coat, therefore, hastened germination. A study of the nut of pili ( Canarium c1,-atum Engl.) by the removal of the shell, cutting the end of the seeds, cracking it slightly with a blacksmith vise, mulching, soaking in water, and scalding, Miras ( 10) ebtained favorable results. Removal of the shell caused the seeds to start germination in 13 days but the germination was only 34 per cent. Soaking the seeds in tap water for 10 days started germination within 31 days and the germination per cent is the highest per cent of all GRADUATION ISSUE, 1957 methods employed for the species. It was observed that seeds of pili without any treatment starts germinating very much longer than one month. Investigating on lumbang (Aleucites moluccana (L.) Will.) ~eeds to hasten its germination, Tabet ( 13) found that of the three methods used, dibbling the seeds _in nursery bed to a depth of about 2 centimeters and mulching the same with 3 .to 4 inches of cogon grass (lmperata exaltata Brongn.) and watering the bed everyday to make it very wet (about two gallons for every square meter) caused the seeds to start germination within one month and four months to complete germination. The percentage of germination by this method was 86.5 per cent. Lwnbang seeds with one side ground down (similar to nicking) caused the seeds 1 o start the germination one month after sowing and to complete germination required eight or nine months. The germination per cent, by this method, was 21.05. Page 15 Another method employed by Tabat ( 13) was covering the seeds with cogon grass and setting it on fire after they were flpreed evenly on the ground. The seeds were immediately immersed in cold water to crack them. By this method, germination began 18 days after sowing and another month to complete germination; and the percentage of germination was only 24.1. Experimenting also on teak ( Tectona grand is L.f.) seeds Denoga ( 7) approached the problem of hastening the germination by treating the germinating beds and the seeds separately. Various amounts of sawdust, ash, leefmold, peat moss, and horse manure were added and mixed in separate beds. As to the treatment of the seeds, such methods es burning the seeds at various length of time with cogon (Imperata exaltata Brongn.), weathering the seeds in open and shaded pits et various length of time also, and cracking the shell of the seeds were used. The result of the experiment showed that treating the seeds gave better results in inducing early germination than treating the germinating media. The best treatment of the soil to hasten germination is: 1/3 horse dung to 2/3 clayloem mixture. By this method, the germination started in 17 days. The best treatment of the seeds iS storage for 20 days to 60 days in a shaded pit. Germination started within 33 days after sowing with a germination of 69.7 per cent, being the highest. Viability test.-A knowledge of the number of seedlings to be expected on a given area from a lot of seeds is important, because it will obviate the waste of seed and of space in the nursery. For this reason, the viability of seeds should be tested as soons as collected and immediately before sowing or shipping. The percentage of viability should be recorded and kept, aTld should accompany the seed when s!lipped. Page 16 In his experiments on ipil-ipil (Leucaena glauca (L.) Benth.), Banaba (Lagerstroernia speciosa (L.) Pers.), and ipil (lnstia bijuga (Colebr.) 0. Ktze.) Viado (15), found that test by cutting gave a fairly accurate and reliable results and are close to the results of germination tests. In this experiment, he compared the results of each of the three methods of testing viability, i.e., cutting test, physical test and germination. He is of the opinion that "cutting t€st" gave comparatively good results, considering the simplicity and rapidity of use. His results were as follows: Species Ipil-ipil Banaba Ipil Cutting Test Germination Test Per cent Per cent 29.0 27.0 30.5 34.5 77.0 70.0 CONCLUSIONS AND RECOMMENDATIONS The results of these studies reveal several interesting facts, the merits and demerits of which are discussed here for evaluation. 1. The results of the studies of Acu:iia ( 1) and Lopez ( 9) reveal that seeds need proper storage to prolong their viability; and that a storage method good for one species may not be good for another. Al· though only a few studies have been conclucted on this subject, the results may be useful in the proper method of storing seeds to maintain their viability for a longer period. 2. The experiment of Viado ( 15) on "cutting'' for testing viability is considered a reliable, practicable, easy and rapid method with big seeds. However, this may not be practicable with hard-shelled seeds like pili and lumbang, because the seed coat is too hard for the knife to cut. Neither is it possible with small or tiny seeds. 3. Defensor ( 5) found that the density of sowing hes some direct relationship to mortality caused partly by damping-off but that this does not have any direct effect on FORESTRY LEAVBS the percentage of germination. While this :s true, there are other effects of the density of sowing because as the seedlings grow bigger, they compete not only for crown E!pace but also for soil moisture and soil 11utrients, as their roots spread in the ground. The growth will show some of the effects of density of sowing. This, however, needs further study. 4. The experiments of Quimpo (12), Caguioa ( 3) and Denoga ( 7) on the effects of depths of sowing on the germination and quality of seedlings indicate that f.eeds require well aerated soil for germination, and as a general rule sowing at from 2 to 10 centimeters in depth favor germination. Deeper than these depths were found ~o be injurious to the seed and this may be another cause of mortality of seedlings and decrease of the percentage of germination. 5. In the studies on seed treatments, the i·esults showed that one treatment is good for one species of seeds but not for another. The variations in the findings in the different studies may be attributed to the difference in the types of seeds, the character of treatment, the time of the year, and other factors. It has been proved, however, that certain types of seeds as cartilaginous and hard coated seeds need some pre-treatment ~o hasten their germination. 6. Caguioa's experiment on the use of ~erminating media showed that not all types of soil are fit for the germination of seeds and the development of seedlings. The studies presented in this paper show the extent of research conducted in the Division of Forest Investigation on forest tree seed germination. Considering the number of important tree species used in our reforestation projects, the necessity of an immediate and more concerted effort toward more researches along this line is in order. It is an accepted fact that in the studies of natural reproduction of forests, the start should be made with the seed and seed production of stands. A better knowledge of the behavior of tree seeds is required GRADUATION ISSUE, 1957 not only for successful propagation of trees in nurseries for reforestation and ornamental purposes, but also for the intelligent control of forestry operations to assure natural and artificial regeneration. BIBLIOGRAPHY 1. AC~A. R. A.-The effect of storage on the germination of West Indian Cedar (Cedrela odoratti Linn.). Philippine Journal of Forestry, 1. 3:293-299; (1938); Makiling Echo XII, 10:263 (1934). 2. BALDWIN, H. 1.-Forest Tree Seed. Chrc; nica Botanics Company. Waltham, Mass., U.S.A. { 1942). 3. GAGUIOA, V.-Effects of different depths of aowing on the germination of alupag seeds. Makiling Echo XV. 2:106-124 (1936). 4. ------'Germination and early development of white lauan seeds under various media. Philippine Journal of Fores.try 1. 1:65-77 (1938); Makiling Echo XV. 2 (1936). 5. DEFENSOR, V. J.-Effect of the density of sowing on the germination of seeds of Benguet Pine. Ma.kiling Echo XIV. 1:57-58 (1935). 6. DELIZO, T.-Hastening the germination of akle. Philippine Journal of Forestry 1. 1:99-102 (1938). 7. DENOGA, N.-Germination of teak. Philippine Journal of Forestry 2. 2:173-184 (1939). 8. HAWLEY, R. C.-The Practice of S"ilviculture. Fifth edition, John WHey & Sons, Inc., New York & London (1946). 9. LOPEZ, M.--Storage and germination of largeleaf mahogany seeds. Philippine Journal of Forestry 1. 4:397-410 { 1938). 10. MIRAS, G.-Preliminary treatment of pili seeds to hasten germination. Makiling Echo XIV. 1:60-61 (1935). 11. PARAS, V.--Comparison of the different methoda of germinating bitaogl. Philippine Journal of Forestry 2. 1:57-64 (1939); Makiling Echo XIV. 2:105 (1935). 12. QUIMPO, T.--Effects of depths of cover on germination of large-leaf mahogany. Makiling Echo XVI. 3:199-211 (1937). 13. TABAT, E.-Germination of lumbang. Maki.ling Echo XV. 4:1-25 (1925). 14. TOUMEY, J. W. and C. F. KORSTIANSeeding and planting in the practice of Forestry. Second edition. John Wiley & Som, Inc., New York (1931). 15. VIADO, J.-The cutting test as a practical method of testing the viability of seeds. Philippine Journal of Forestry 1. 2:219-226 (1938). Page 17