The Preliminary Studies On Hard Seed Formation Mechanism And Breaking Methods Of Three Legume Species

Hard seed is a common phenomenon in the plant kingdom, the hard seeds rate variesaccording to the different seed maturity and the external conditions. Hard seeds which theseed coat （sometimes including the peel） are hard and difficult to imbibe and germinate. Hardseed are impermeable, So, the phenomenon of sprout deficiency and duanlong offen occurhappen in the production, appropriate treatments are usually applyed to improve thepermeability of the seed coat, germination. Therefore, formation mechanism and method ofbreaking of hard seed were studied in this paper; it is an important of significance to guideagricultural production.In this paper using Robinia pseudoacia L., Gleditsia sinensis Lam., Albizia julibrissinDurazz. as the research object, research formation mechanism and get rid of hard seed. Thesismainly through the the seeds develop process and anatomical characteristics; the formationcauses of the hard seeds was studied; the influences of temperature,temperature andconcentrated H₂SO₄mixing treatment effects on the getting rid of the hard seeds and impactyon seedling vigor were also discussed, provide technical support for the three seed andseedlings production.The result showed that three kinds of tree legume species seed coat have the typical hardseed structure characteristics, the Robinia pseudoacia L. seed coat structure mainly includes:cuticle, palisade tissue, bone-shaped cell layer, the spongy tissue; the Gleditsia sinensis Lam.seed coat structure include: cuticle, open wire, two layers of palisade cell layer, bone-shapedcell layer, the spongy tissue; the Albizia julibrissin Durazz. seed coat structure include: cuticle,open wire, palisade cell layer, bone-shaped cell layer, sponge organization.Using different temperature of the water to deal with the Robinia pseudoacia L. seeds,the best treatment is90℃. After concentrate H₂SO₄at different times, then using60℃waterto breaking hard seeds, the results are following, for H₂SO₄-60℃combined treatment thebest concentrate-H₂SO₄soaked time is30min; After concentrate-H₂SO₄at different times,then using90℃water to breaking hard seeds, the results are following, for H₂SO₄-90℃combined treatment the best concentrate-H₂SO₄soaked time is20min; Using differenttemperature of the water to deal with the Gleditsia sinensis Lam. seeds, the best is80℃.Afterconcentrate-H₂SO₄at different times, then using60℃water to breaking hard seeds, theresults are following, for H₂SO₄-60℃combined treatment the best concentrate-H₂SO₄soaked time is30min; After concentrate H₂SO₄at different times, then using90℃water to breakinghard seeds, the results are following, for H₂SO₄-90℃combined treatment the bestconcentrate-H₂SO₄soaked time is20min; Using different temperature of the water to dealwith the Albizia julibrissin Durazz. seeds, After concentrate H₂SO₄at different times, thenusing60℃water to breaking hard seeds, the results are following, for H₂SO₄-60℃combined treatment the best concentrate H₂SO₄soaked time is30min; After concentrateH₂SO₄at different times, then using90℃water to breaking hard seeds, the results arefollowing, for H₂SO₄-90℃combined treatment the best concentrate-H₂SO₄soaked time is10min.Temperature treatment obviously promoting germination of three hard seeds. The mainreason was that high temperature can make to seed crack and improve seed gas exchange,relieve seed dormancy and promote seed germination. High temperature seed-soaking canchange the permeability of seed coat, improve the germination rate, etc., but if thetemperature is too high it will damage the seed internal material, result in the adverseconsequences, such as the vigor index and root activity decline.High seed soaking temperature can effectively eliminate the hard seed, but also damagethe seed for the embryo, make the seeds losing the value as seed material, the low seedsoaking temperature have not serious damage, but decline of hard seed rate is very small, thepurpose of to break seed dormancy is not attained. How many different degrees of soakingwater depend on the hard seed rate and hard seed degree.Because of the hard seed and the normal seed mixe together, the handle hard seedtreatment methed is to adopt successive increase water temperature.Concentrate-H₂SO₄treatment can obviously promote three kinds of hard seedgermination. The main reason is that H₂SO₄has oxidation effect, can corrode seed coat,promote the seed early water uptake, which is especially significant for some hard seeds.Using90℃water and Concentrate-H₂SO₄treated seed, the best germination rate was66.3%which20min concentreate-H₂SO₄treatment, and germination index and vigor index werealso higher. However, for the highest root activity treatment time,10min is best. Reason maybe that H₂SO₄treatment time can break hard seeds better, to some extent, but also damage theroot vigor of seed.