[Effects of nitrogen application level on photosynthate distribution of Korla fragrant pear trees]. / æ–½æ°®æ°´å¹³å¯¹åº“å°”å‹’é¦™æ¢¨å ‰åˆäº§ç‰©åˆ†é çš„å½±å“.

Using 13C pulsed labeling technique, we examined the biomass and carbon accumulation of different organs as well as the distribution characteristics of 13C assimilate of 6-year-old Korla fragrant pear trees under three nitrogen application levels, i.e., 150, 300, and 450 kg N·hm-2 (marked as N1, N2, and N3, respectively). Results showed that the biomass, carbon accumulation, 13C fixation and leaf assimilation capacity of the whole pear tree increased while root to shoot ratio decreased with increasing nitrogen application. Both biomass and carbon accumulation amount of reproductive organs (i.e., fruits) were the highest under N2 treatment. The 13C content and distribution rate of each organ changed dynamically along with increasing nitrogen application. At the new shoot growing stage, leaves and roots had stronger competitive abilities for photosynthate, with 13C distribution rates being the highest under N1 treatment. During fruit swelling and mature stages, leaves and fruits were more competitive, with 13C content and distribution rate in leaves being the highest under N3 treatment and those in fruits being the highest under N2 treatment. According to the absorption and distribution characteristics of carbon assimilate across organs under the three nitrogen application levels, the optimal nitrogen application level for achieving high fruit yield in the 6-year-old Korla fragrant pear tree orchard is recommended as 300 kg·hm-2 .

[Characteristics of absorption, utilization, and distribution of 15N-urea for Korla fragrant pear in spring.] / 库尔勒香梨春季施用15N-å°¿ç´ çš„å¸æ”¶ã€åˆ†é å’Œåˆ©ç”¨ç‰¹æ€§.

Six-year-old Korla fragrant pear trees were fertilized with 15N-labelled urea before early bud stage to examine the absorption, distribution, and utilization of urea. Results showed that there was a significant difference of 15N distribution rate in organs at different growth stages. 15N was pre-ferentially distributed in the roots , with Ndff (15N amount absorbed from the fertilizer contribution rate of the total nitrogen organ) being the highest in roots following by new shoots at full-bloom stage. During new shoot growing and fruit expanding stages, 15N absorbed in roots preferentially moved to new organs (leaves and new shoots), with 15N distribution rate to roots being continuously decreased. Fruits became the new distribution center with highest Ndff at harvest stage. The amounts of absorbed 15N in fruits accounted for 19.8% of total absorbed 15N in the tree. The utilization rate of 15N-labelled urea at current season increased gradually with the growth stages. The maximum value of utilization rate was 18.5%, which was observed at harvest stage.

[Responses of main characters of root system to salt stress among cotton varieties with diffe-rent salt tolerance]. / ä¸åŒè€ç›å“ç§æ£‰èŠ±æ ¹ç³»ä¸»è¦æŒ‡æ ‡å¯¹ç›åˆ†èƒè¿«çš„å“åº”.

A pot experiment was carried out to test the effects of salt levels on root morphology as well as the relationship between root morphology and salt tolerance with four cotton cultivars (salt-sensitive cultivar CCRI45, weak salt-resistance cultivar XLZ17, moderate salt-resistance cultivar XLZ13 and salt-resistance cultivar CCRI35). Results showed that dry mass and K+/Na+ ratio of cotton root and leaf were significantly reduced by salt stress. Dry mass of root and leaf and K+/Na+ ratio of root of cultivars XLZ13 and CCRI35 were 69.3%-104.4%, 24.8%-45.3% and 25.0%-45.8% higher than those of cultivar CCRI45, respectively. Root development was significantly restrained by salt stress. Total root length, total root surface area and total root volume of cultivars XLZ13 and CCRI35 were 15.2%-85.8%, 12.0%-68.5% and 31.7%-217.8% higher than those of cultivar CCRI45, respectively. Furthermore, the length of fine and middle roots, root surface area and root volume of cultivars XLZ13 and CCRI35 in 0-10 cm soil layer were 27.2%-73.9%, 39.6%-74.3% and 99.0%-309.7% higher than those of cultivar CCRI45, respectively. Results from principal component analysis showed that the variations of specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer among cultivars was significant. Specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer were the main root characters to distinguish different salt tolerant cotton cultivars. Results from the stepwise regression analysis showed that specific root length, coarse root length, coarse root area, and coarse root volume at 0-10 cm and 10-20 cm soil layers, as well as fine root area and middle root ratio at 0-10 cm soil layer were sensitive to salt. Salt tolerant cultivar adapted to salt stress through increasing root length ratio, fine length ratio, and specific root length.

[Effects of phosphorus fertilization on biomass accumulation and phosphorus use efficiency of trellis-cultivated melon].

A field experiment applying six rates of P fertilizer (P2O5, 0, 150, 225, 300, 375 and 450 kg . hm-2, respectively) was conducted to investigate the effects of P fertilization on dry matter accumulation (DMA), P uptake and accumulation (PUA) and P use efficiency (PUE) of trellis-cultivated melon. Results showed that, P application increased DMA and PUA, for 150 and 225 kg P2O5 . hm-2 treatments, being 19.9% and 26.3%, 23.0% and 26.3% higher than that in no P fertilizer treatment at fruiting stage. With plant growth, DMA and PUA of different organs and the whole plant gradually increased. DMA and PUA were mainly distributed in the leaves during the early stage of the growth and in the fruit during the latter stage. P application decreased the recovery efficiency of applied P (REP), agronomic efficiency of applied P (AEP) and partial factor productivity of applied P (PFP). At 150 kg . hm-2 P application rate, the maximum REP, AEP and PFP were 11.1%, 152.9 kg . kg-1 and 476.3 kg . kg-1, respectively. Compared with no P fertilizer treatment, melon yields of 150 and 225 kg P2O5 . hm2 treatments increased by 47.3% and 39.7%, respectively. In summary, the vining stage and fruit expanding stage were the key periods for P application in trellis-cultivated melon system. Based on synthesized economic yield and P fertilizer efficiency, the recommendation of P fertilizer for trellis-cultivated melon is 150-225 kg P2O5 . hm-2 under the climatic condition of the experimental area.

[Research on the relevance of earthworms inducing soil Cd2+ absorbed by perennial ryegrass].

Through the method of simulating the heavy metal pollution in farmland, the graphite oven (GF-990) atomic absorption was used for analyzing the regulations of the earthworms inducing the soil Cd2+ absorbed by the perennial ryegrass. The result indicated: (1) under the circumstance of the soil Cd2+ density of 3-6 mg x kg(-1), the positive relevance appeared extremely remarkably that the contents of Cd2+ in underground portions of the perennial ryegrass relate to the earthworm quantity (r = 0.883 2-0.986 2), but in the portion above ground the positive relevance did not appear extremely remarkably (r = 0.345 5-0.325 4); And the negative relevance appeared remarkably that the contents of Cd2+ in the soil relate to the earthworm quantity (r = -0.588 7(-) -0.678 4). (2) Under the conditions of isometric number of earthworms, the more the density of Cd2+ in the soil, the more the increase of Cd2+ in both portions under and above ground of perennial ryegrass. (3) Under the same soil environment, the negative relevance appeared that the number of earthworms relates to the contents of Cd2+ in the earthworms (r = -0.982 0(-) -0.991 6).

[Comparative analysis of endogenous hormones between two species of Ammopiptanthus seedlings around germination and under Pb2+ stress].

The changes in three endogenous hormones, phytohormones gibberrelic acid (GA3), indoles-3-acid (IAA) and abscisic acid (ABA), were studied around germination and under tress of different density of Pb2+ between two species of Ammopiptanathus. It was found that (1) around germination, in Xinjiang Ammopiptanthus the rate IAA decreased 77.80%, and the rate of ABA decreased 98.90%; and in Mongolia Ammopiptanthus the rate of IAA decreased 75.80%, the rate of ABA decreased 66.20%, and the GA3 contents in both had no big change. (2) With the increase in Pb2+ concentration (20-1 500 mg x L(-1)), the IAA decreased significantly; and only under the high density (more than 1 000 mg x L(-1)) of Pb2+, the GA3 was affected by it; the ABA did not change regularly. So the three endogenous hormone levels of Mongolia Ammopiptanthus were higher than those of Xinjiang Ammopiptanthus. (3) the distributions of Pb2+ in Ammopiptanthus seedlings are the root > stems > leaves. (4) the stress of high concentration of Pb2+ damages irreversibly the leaf cells of Ammopiptanthus. This study can provide the basis of reference data for further research on the growth characteristics, resilience and the mechanism of specific broad-leaved evergreen shrubs-Ammopiptanthus in desertification area.