BREAKING THE DORMANCY OF PEACH SEED BY TREATMENT WITH THIOUREA

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Abstract
34 lots of peach seed, including 23 vars., were treated with various concs. of thiourea in aqueous solns. The dormancy of Lovell peach seed was broken by treatment with thiourea. Of the 22 other vars., similarly treated, the dormancy of 6 was not broken, 10 germinated 10%, and all remaining vars. responded to a lesser degree than did the Lovell. Lovell seedlings which developed from non-after-ripened seed whose dormancy was broken by treatment with thiourea were dwarfed, with shortened internodes and anomalous leaves, typical of seedlings from non-after-ripened, excised embryos. Complete after-ripening of peach seed accomplishes more than a conditioning of the seed to germinate; it also involves changes in the seed, which result in vigorous seedlings free from dwarfish and anomalous characters. The most favorable treatments to break the dormancy of non-after-ripened Lovell seed were soaking for 2-16 hrs. in 0.25-0.5% aqueous soln. of thiourea or placing in a continuous supply of 0.25% soln. Lovell seed which was treated with thiourea while still enclosed in the stony pericarp failed to germinate, but germinated when removed from the pericarp. Seed coats of after-ripened Lovell seed were checkered in appearance and the cotyledons became enlarged during germination; non-after-ripened, thiourea-treated Lovell seed did not have this appearance and did not enlarge in this way. Molds and common seed-borne fungi were reduced by treatment of seed with thiourea.