Study On Seedling Age And Harvest Date During Producing Carrot Seeds By The Seed-to-Seed Method

The study was designed separately three distinct seedling age (60d,75d and 90d) and three difference harvest date (45d,50d and 55d) to study the influence of the seedling age (sowing time) and harvest date on growth and development of stecklings, yield and quality of seeds in process of producing carrot seeds by the seed-to-seed method, and expected to solve low breeding coefficient and high production cost in the process of collecting carrot seeds by the root-to-seed method. A series of indexes such as growth and development, seed yield, seed vigour and the value of POD, SOD, CAT, EC (electrical conductivity) were analyzed. The test was adopted the single element and completely random design, The results could be concluded as follows:1. Steckling of seedling age of 75d grew quickly at seedling stage. Their plant height and leaf number were higher than those of 60d seedling age apparently. At seedling stage, the plant height of steckling among three seedling ages was positively correlative with the FW per plant most markedly.2. The steckling of each seedling age started to grow quickly after transplanting. Survival rate and other indexes were higher in the steckling of 75d seedling age than those of 90d seedling age, but did not differ significantly from the 60d seedling age .The growth speed of female plants of each seedling age was higher than that of male.3. The bolting speed was different due to different seedling ages. The bolt peak appeared very early in the female stecklings of 90d and 75d seedling age .Their final bolting percent were up to 77.4 % ,79.3 % separately, higher than that of 60d seedling age steckling remarkably. The bolting peak in the male steckling of 90d and 75d seedling age appeared earlier a month than the 60d seedling age.4. The days of all growth stages in carrot were shorted with the seedling age longed (sowing time was earlier). Days from transplanting to bolting or to floral initiation among steckling of three seedling ages separately were compared. The disparity was very significant respectively, in the treatment of the seedling age of 90 days was shortest and the seedling age of 60d was longest. During these days from transplanting to bolting or to floral initiation, The effective accumulative temperature among three seedling age presented the same regular pattern respectively.5. Yield per plant and seed yield of primary umbel from steckling of 75d seedling age were higher than those of other treatments markedly. Average 1000 seed weight from steckling of 75d seedling age was higher than that of 60d seedling age. but not apparently differ from 90d seedling age remarkably. At the same time, seed yield per 667m~2 from steckling of 75d seedling age up to 93.5kg, and was higher than that of 60d and 90d seedling age.6. A series of indexes such germination vigour and germination uniformity were compared among seeds from primary umbel of three seedling ages, and the discrepancy was not significant. The germination vigour and germination uniformity of seed from secondary umbel become highest in the treatment of 75d seedling age. POD. SOD, CAT of seeds from steckling of 75d seedling age were increased and EC was reduced most markedly.