Lodging Resistance And The Response To Cultivation Measures Of Oilseed Flax

Low yield of oilseed flax is largely related to the lodging, which limits the development of oilseed flax. It is extremely important to investigate the characteristics and inner mechanisms of lodging resistance, the effects of the interactions of water and nitrogen, and plant density on lodging characteristics and yield, the findings of which will have significant effects on optimizing the cultivation techniques of oilseed flax. This article is initiated from an experiment conducted in Yuzhong Breeding Station, Lanzhou, Gansu Province. Based on the field experiment(different varieties, different combination of water and nitrogen and different plant densities), the characteristics related to lodging-resistance that include stem morphology, physiological and biochemical properties, and mechanic properties have been investigated, along with the studies on the effects of cultivation on lodging-resistance and yield, which will be supportive to the cultivation techniques of lodging-resistance and high yield in oilseed flax. The major findings are as the following:1.There were variations on lodging rate, morphological characteristics, physical properties, stem physiological and biochemical ingredients content and mineral contents among different varieties of oilseed flax, among which the variation index with the value between 1.79% and 181.7%. It has indicated that lodging rate was positively related to plant height, gravity centre height, lodging index and the content of nitrogen and magnesium; however it was negatively related to stem diameter, culm wall thickness, above-ground dry weight, root dry weight, lodging resistance, content of cellulose and lignin in stem, and enzyme activities of PAL、POD、CAD、4CL and TAL, as well as the content of potassium and calcium.2. The cluster analysis was based on 15 lodging-resistance-related indexes, 10 varieties of oilseed flax have been categorized into 3 groups. The Group I were high lodging-resistance varieties which including Longya 8, Longya 9, Longya 11 and Lunxuan 3. The Group II were middle lodging-resistance varieties which including Longya 10, Longyaza 1, Tianya 9 and Dingya 22. The Group III were low lodging-resistance varieties which including Zhangya 2 and Dingya 23.Lodging rate,plant height, gravity centre height, lodging index and the content of nitrogen and magnesium of stem showed as Group I<Group II<Group III.As well as stem diameter, culm wall thickness,dry weight,lodging resistance, the content of cellulose, lignin, potassium and calcium of stem showed as Group I>Group II>Group III.The characteristics of high lodging resistance varieties including low lodging rate, low plant height, gravity centre height as a result of strong stem, thick culm wall, well-developed root system, strong lodging-resistance, low lodging index, the high content of cellulose, lignin, potassium and calcium and the low content of nitrogen and magnesium.3. With the increased irrigation, the plant height and gravity centre height of oilseed flax increased responsively, however, stem diameter and culm wall thickness decreased. Exceeded irrigation is not applicable for the increment of soluble sugar, starch, cellulose, and lignin in stem, meanwhile, the activities of the enzymes(PAL、TAL、CAD、4CL and POD) that were synthesised by lignin decreased. However, the exceeded irrigation will promote the content of N、K、Mg, but limit the content of Ca. Stem strength and lodging-resistance index decreased with more applied irrigation. With the more application of nitrogen fertilizer, the plant height and gravity centre height of oilseed flax increased respectively with higher content of N, Mg and lower Ca in the stem. Under W1 and W2 irrigation conditions, as the applied nitrogen fertilizer was between 0 kg·hm-2(N0) and 112.5 kg·hm-2(N2), stem diameter, culm thickness, the content of soluble sugar, starch, cellulose and lignin in the stem has increased as well as the activities of 5 enzymes(PAL、TAL、CAD、4CL and POD) and the content of potassium and stem strength. When the applied nitrogen fertilizer was between 112.5 kg·hm-2(N2) and 225kg·hm-2(N3), all the indexes were in a decreasing trend. Under the condition of W3 irrigation, with the more applied nitrogen fertilizer, every indexes in terms of the break point, it was at the level where the applied nitrogen fertilizer was 37.5 kg·hm-2(N1). Therefore, water and nitrogen coupling on lodging resistance traits had significant interaction effects.With the exceeded irrigation, the seeds per fruit indicated a parabolic trend. Capsule number per plant increased gradually, grain weight and yield increased between W1 and W2; however, the one that between W2 and W3 didn’t change significantly. With the application of increased nitrogen fertilizer, Capsule number per plant, seeds per fruit, grain weight and yield indicated an increment at the beginning, and then decreased slightly. Therefore, the exceeded or insufficient irrigation and applied nitrogen fertilizer were not helpful for the production.4. With the increased plant density, the plant height and gravity centre height increased; however, the stem diameter, culm wall thickness, above- and below- ground fresh and dry plant weight increased, and the content of cellulose and lignin indicated a decreasing trend, the enzyme activities of PAL、TAL、4CL and CAD decreased along with a reduced stem strength and low lodging-resistance index. High density cultivation has made less seed number per capsule; however, it will promote capsule number per m2. By changing capsule number per m2 to approach an acceptable level of high density cultivation will increase the yield production.