Effect Of Onion Bulb Cultivating Dates On Characteristics Of Growth And Development In Seed-Plants

Onion (Allium cepa L.) is one of Chinese major export vegetables, and it`s cultivation area and total output rank is first all over the world. Because of onion breeding and the eximious species breeding technique is laggard in China, cultivars mainly depend on imports. Onion is gren-vernalization crops, which only determine a reasonable cultivating dates in order to ensure that both kinds of good vegetation growth, but also a timely manner through the low-temperature vernalization, the better to maintain the reproductive growth. This experiment established four treatments that the bulb cultivating dates for 20th September (T1), 10th October (T2), 30th October (T3) and 20th November (T4), for studying effect of onion bulb cultivating dates on characteristics of growth and development in seed-plants in Shandong area. The main results are as follow:1. Different cultivating dates of onion bulbs had a significant effect on growth in seed-plants. The plants of T1 grew better before winter, but the plants grew worse nest spring. The vegetation growth of T4 was restrained and harmful for bolting and seeding next spring. The plants of T2 and T3 were different in growth at prophase, and had not distinct diversity at anaphase. They grew vigorously and had thickest flower stem, the plant height of T3 was up to 64.9 cm, bolt height was up to 120.0 cm and FW of stems and leaves up to 557.0 g per plant, which were higher than T1 by 17.36%, 16.85% and 34.54%, and higher than T4 by 29.80%, 4.99% and 42.46%.2. Different cultivating dates of onion bulbs had a significant effect on photosynthetic ability and chlorophyll fluorescence in seed-plants at bloom-growth period. The plants of T2 and T3 had higher chlorophyll content and their Pn was higher than T1 by 6.50% and 17.89%, and higher than T4 by 9.17% and 20.83%. T2 and T3`s bolts were similar in Pn. Otherwise the Fv/Fm and qP of T2 and T3 leaves significantly higher than that of T1 and T4, enhance photosynthetic ability and augment photosynthetic matter manufacture and accumulated.3. Different cultivating dates of onion bulbs had a significant effect on senescence in seed-plants. The plants of T1 and T2 spouted before winter. Seed-plants leaves SOD, POD, and CAT activity reduced during the winter. In parallel, activity of them increased gradually returns growing the next spring, but the activity was lower than that of T3 and T4. In contrast, the variation of the leaves membrane permeability and MDA content was reverse. The effect of bulb cultivating dates on bolting date was little, but the variation of SOD, POD, and CAT activity in the bolts was similar with that of leaves, which indicated that compared with cultivating lately, the seed-plants of early cultivating dates was early senescence.4. Different cultivating dates of onion bulbs had a significant effect on absorption and distribution of mineral elements in seed-plants. All kinds of treatments growth less before winter, the absorption of the mineral elements were less, but which was higher in the bloom-growth period and flowering period. Distribution rate of the nitrogen, phosphorus and potassium up to the max on April 8th in onion seed-plants, and T2 and T3`s higher, and distribution rate of the nitrogen, phosphorus and potassium of T3's leaves was 82.20%, 70.51%, 77.34%. Distribution of mineral elements of bolts and ball-flowers increase gradually when onion bolting, and T2 and T3 was higher.5. Different cultivating dates of onion bulbs had a significant effect on seed yield and quality in seed-plants. The seed production of T2 and T3 is higher in four treatments, above 50 kg/667m2 in two annual. T4 followed by planting of onion 42.47 ~ 44.92 kg/667m2, and T1 minimum, only 33.28 ~ 37.28 kg/667m2. The weight of per thousand seeds was accordant with seed yield. The plants of T3 was of 4.05 ~ 4.07 g higher than others, and T1 was 3.86 ~ 3.90 g lower than others. Moreover, the seed germination vability and germination rate of T2 and T3 was higher, the seed germination rate was 92.2% ~ 96.2%, T4 followed, and the T1 was min.The test results indicated that the proper period for onion bulbs'cultivating was from 10th October to 30th October in Shandong.