Studies On The Relationship Between Root Growth And Plant Growth In Alfalfa

With the adjustment of agricultural structure and rapid development of dairy industry, the demand for high yield and quality forages is increasing in southern China. Alfalfa(Medicago sativa L.) is a major forage crop with high quality cultivated all over the world, but it's cultivation in south china was limited due to the hot and humid weather and soil condition. In recent years, with more and more alfalfa products introduced into southern area, scientific researchers regard seasonal production of alfalfa as the major planting pattern and research trend, according to the ecological condition and planting system of the southern area.In order to select alfalfa root traits of great comprehensive characters for seasonal utilization in south China, a study with 9 alfalfa cultivars at seeding, branching and blooming stage was separately conducted to testify the root growth and its relation to the growth of up ground parts.At seeding stage, collar diameter of the cultivars had a remarkable increase at the 6th leaf stage, and a significant difference was observed among the cultivars at the 7th leaf stage. Lateral roots on taproot were concentrated at 0-5 cm closed to collar. There was an obvious difference in root dry matter among 9 alfalfa cultivars since the 5th leaf stage, and there was a significant difference in the increment and growth rate of root dry matter among 9 alfalfa cultivars. At the late seeding stage, root decayed from the end, because of the hot and humid weather, which restricted the plant growth. Water cultures should avoid the hot term.At branching stage, root traits differed among 9 alfalfa cultivars. There was a difference in diameter of taproot and collar, which had a decisive impact on the growth of other root morphology,. Especially the taproot growth had an important impact on plant growth. Stronger taproot and collar had a higher potential to grow lateral roots and to accumulate more root dry matters. The maximum root dry matter was 0.19～0.50 g·plant-1. Lateral root density on taproot was high at 0～5 cm closed to collar. There was a significant difference in plant traits among 9 alfalfa cultivars. The maximum dry matter yield was 1.44 g·plant-1. Primary shoot numbers, plant height and single leaf area all had a high relation with dry matter yield. Root traits had significant or great significant correlation with plant growth traits.The result of the blooming stage was generally consistent to that of the branching stage. Taproot diameter and collar diameter had a prominent performance. In addition, growth rate had a greatly significant correlation with dry matter yield. The greatest taproot diameter and collar diameter were 7.54 mm and 9.57 mm, respectively. Root dry matter was 1.64～4.19 g·plant-1. The dry matter yield ranged 7.82～26.57 g·plant-1. The biggest single leaf area was 1882.8 cm2.Above mentioned results showed that there were significant differences among root and plant growth traits. Taproot diameter and collar diameter played major role in root growth, and had an important impact on plant growth. Strong collar was an important basis for growing shoots. Strong taproot, thicker collar and more lateral root numbers, which made more primary shoots, were important factors influencing dry matter yield. Strong taproot, thicker collar and more lateral root numbers were important root characters of alfalfa cultivars for short-term cultivation in south China, which had potential to produce more dry matter yield.