Study On Cotton Root Growth And Physiological Characteristics And Their Relationship With Cotton Shoot In The Central-South Region Of Hebei

In this study, the properties of root growth and distribution in cotton under different planting densities and different pruning ways have been investigated based on soil core sampling method. Six planting densities treatments and two pruning treatments within two densities were conducted using transgenic genotype Nong Da 8 as experimental material. Then, correlations between characteristics of roots and those of aerial parts were also studied. The purpose of this study was to explore the effects of different planting densities and pruning ways on the growth and distribution of cotton root under field condition. Simultaneously, bleeding sap weight, content of some nutrition elements in bleeding sap and bleeding sap relation to soil water had also been analyzed. The result showed that:1. Under different density treatments, both root dry weight above 0-60cm soil layer and root length were gradually increasing before the beginning of boll opening stage when reached the highest of density of 1.5～8.7×10⁴ plants·hm^-2 . However, the above root traits reached the highest at the peak bolling stage under the density of 10.5×104 plants·hm^-2, and showed a descending trend at the beginning of boll opening stage.2. At the early growth and development stage, the root ry weight and the root length of high density were higher than low density. The root dry weight under density of 3.3×104 plants·hm^-2 was the highest and the root length under 5.1×10⁴ plants·hm^-2 was the highest .There was no significant difference between planting densities on roots systerm.3. The perpendicular distribution of root was effected by planting densities at different growth stages. At budding peak stage, the root dry weight in single soil layer was increased along with the increase of planting densities. The root length in 10-20cm soil layer was higher than in 0-10cm. From early-flowering stage to peak bolling stage, the root dry weight and root length in top soil layer (0～20 cm) of low densities (1.5×104 plants·hm^-2, 3.3×104 plants·hm^-2) were lower than other high planting densities (6.9×104 plants·hm^-2, 8.7×104 plants·hm^-2, 10.5×104 plants·hm^-2). The low planting densities mentioned previously had lower above root traits than the high planting densities in deep soil layer (30～60cm) at growth phase , but the root dry weight of low planting densities in top soil layer (0～20 cm) was higher. The root dry weight and root length of density of 10.5×104 plants·hm^-2 were lower than other planting densities. 4. Correlations between the root dry weight, root length and planting densities and impact significance were different at different stages. The correlation between the root dry weight or root length in top soil layer and planting densities was significantly positive at early stage. The correlation between the root dry weight or root length in deep soil layer and planting densities was significantly positive at middle stage. The root dry weight or root length in top soil layer and planting densities was in negative correlation at later stage.5. The root surface area showed an increasing trend"S"type under different planting densities, but the root surface area of density of 10.5×10⁴ plants·hm^-2 began to decrease in the beginning of boll opening stage. From budding peak stage to early-flowering stage, The correlations between the surface area and planting densities was significantly positive correlated, the surface area increases gradually under middle densities at later stage. In the whole growth period, the average diameter in 0-40cm continuously decreased when the depth continuous increased, while the average diameter in soil layer below 40cm increased at first and then decreased.6. In the whole growth period, the root dry weight and root volume of simplification pruning was higher than common pruning in the same density. The root dry weight and root volume of 6.9×10⁴ plants·hm^-2 was higher than of 3.3×10⁴ plants·hm^-2 on simplification pruning, but was lower on peak bolling stage. The root length and root surface area of simplification pruning were higher than common pruning at different stages. The root length under high densities was higher than low densities on simplification pruning, and ofdensity of 3.3×10⁴ plants·hm^-2 was higher than 6.9×10⁴ plants·hm^-2 from peak bolling stage.7. The perpendicular distribution of root was obviously effected by training type. From budding peak stage to peak bolling stage, the root length in 10-20cm soil layer was higher than in 0-10cm under different treatments, then increased in 0-10cm soil layer at the beginning of boll opening stage. The root dry weight of simplification pruning below 10cm soil layer were higher than common pruning at the beginning of boll opening stage.In the budding peak stage, the average diameter of roots under common pruning was higher than simplification pruning in shallow soil layer. While roots average diameter in deep soil layer perform a reserved trend. In the following growth stages the average diameter of roots under simplification pruning has a dominant position. From the peak bolling stage, the differences between different pruned methods become less obvious. At later stages, the average diameter of roots in single layer soil has no significant difference between different treatments. From the different depths of soil, the average diameter of roots under simplification pruning rises first then falls later with the increase of depth in the earlier stage. At the later stage the average diameter of roots has the trend of sustainable increasimg as the depth increases.8. There was a higher negative correlation between the root dry weight and bleeding sap weight in early stage under different planting densities, and a positive correlation in later stage but not significant. There were effects of planting density, different training types and the both on content of mineral elements in bleeding sap, but there was no significantly rule in this study.9. Correlation between roots and dry matter production, leaf area index is very significant in early stage. The correlation coefficient between roots and dry matter production were more than 0.84 at budding peak stage. While the leaf area indexes were more than 0.86 at budding peak stage and early-flowering stage.