氮肥和底墒对小麦籽粒灌浆过程的调节效应分析

以氮肥和底墒为决策变量,采用最优二次Ｄ饱和设计,用Ｌｏｇｉｓｔｉｃ方程拟合各水肥处理的籽粒充实过程,并推导出一系列次级参数,分别建立了小麦籽粒灌浆强度与持续时间参数的数学模型。结果表明：生长在氮肥或底墒逆境条件下的小麦受精子房的生长潜势（Ｃｏ）较大,并随逆境条件的改善而降低;千粒重（Ｙｏ）与灌浆快增期（Ｔ）的长短、最大灌浆速率（Ｒ＿（ｍａｘ））和平均灌浆速率（Ｒ）无明显相关性,却与起始生长势、灌浆系数（Ｔ·Ｒ＿（ｍａｘ））高度正相关,并且千粒重与灌浆系数的相关性明显大于千粒重与起始生长势的相关性;氮肥和底墒对籽粒灌浆特性具有显著的调节作用。同时还阐述了调节这些参数的水肥栽培途径。     

陕西关中小麦品种更替中性状演变及其发展方向

以关中地区四十年代到九十年代推广种植的主要代表品种及品系为材料,对其分蘖动态、生育期、株高因素、穗部性状、产量、生物学产量、经济系数及冬春性等２０个性状进行了研究,其结果表明关中地区四十代到九十年代小麦品种性状演变的趋势是：冬、春季分蘖变化不大,冬季分蘖趋向略增;春季分蘖趋向略减;成穗数趋向降低,拨节,抽穗和开花期有趋早倾向,而成熟期和总生育天数无明显变化,株高降低极明显（１３７．７－８５．２ｃｍ     

“8455”小麦植株化学成分与麦蚜（长管蚜、二叉蚜）种群消长的关系

通过对两种肥力条件下的“8455”小麦植株化学成分与麦长管蚜和麦二叉蚜种群消长关系的研究与分析,结果表明可溶性糖、含钾量、含水量是影响麦二叉蚜种群消长的主要因子,胱氨酸是影响麦长管蚜种群消长的主要因子。     

麦秸覆盖夏玉米对其苗期生长发育的生化他感作用研究初报

麦秸覆盖夏玉米对其苗期生长发育的生化他感作用研究初报张玉铭,马永清（中国科学院石家在农业现代化研究所,０５００２１）ＡｌｌｅｌｏｐａｔｈｉｃＥｆｆｅｃｔｏｆＷｈｅａｔＳｔｒａｗＭｕｌｃｈｉｎｇｏｎＳｅｅｄｌｉｎｇＧｒｏｗｔｈａｎｄＤｅｖｅｌｏｐｍｅｎ...     

Sucrose and fructan metabolism in wheat roots at chilling temperatures

Sucrose and fructan metabolism were studied in wheat ( Triticuin aotiirum L. cv. Tribal 800) roots during a period at chilling temperature. Enzyme activities related to fructan and sucrose metabolism were measured. Sucrose-sucrose fructosyl transfer-ase (EC 2.4.1.99) activity increased more than 25-fold when plants were cooled to 4°C. Sucrose synthase (EC 2.4.1.13) and sucrose-phosphate synthase (EC 2.4.1.14) activities also increased, but low temperatures had no significant effect on invertaso (EC 3.2.1.26) or on fructan hydrolase (EC 3.2.1.26) activities. The accumulation pattern of fructan in roots was different to that in leaves. In roots chilling stimulated the synthesis of fructans of high degree of polymerization.     

Studies of 13C in the foliage reveal interactions between nutrients and water in forest fertilization experiments

The severity of a root rot disease of cereals, caused by Rhizoctonia solani Kühn AG8, was inversely correlated to the Zn status of plants in field studies in 1989 and 1990. In 1989, a preliminary survey was conducted in a farmer's field in South Australia where Zn deficiency and disease were both widespread. Zn concentration in Spear wheat plants at the 3-leaf to early tillering stage was negatively correlated with severity of the disease. For the elevent elements analysed, a correlation matrix showed that Zn had the highest, and only significant (R²=0.52^**) association with disease. The effect of Zn applications and their residual value on disease severity was further studied in a long-term field experiment in 1989 and 1990 to which Zn had been applied in 1986. There was a decrease in the area of Rhizoctonia bare patch as Zn rate was increased, a result consistent with the field survey results; the recommended rate of 2.5 kg Zn ha^–1 reduced the area affected by bare patch from 42% to 21% of the total crop area compared with no Zn application, overcame Zn deficiency and increased grain yield from 1.1 to 2.8 t ha^–1. In 1990, fresh Zn application treatments were applied to trial plots designed for this purpose, in order to compare the response with the older Zn treatments applied in 1986. The areas of bare patch in the older Zn treatments were approximately 5% greater than those in the fresh Zn treatments. The results are consistent with the hypothesis that Zn deficient plants are more susceptible to root rot caused by R. solani. Testing this hypothesis is the subject of a companion paper.     

Aluminum enhancement of plant growth in acid rooting media. A case of reciprocal alleviation of toxicity by two toxic cations

The generally rhizotoxic ion Al³⁺ often enhances root growth at low concentrations. The hypothesis that Al³⁺ enhances growth by relieving H⁺ toxicity was tested with wheat seedlings ( Triticum aestivum L.). Growth enhancement by Al³⁺ only occurred under acidic conditions that reduced root elongation. Al³⁺ increased cell membrane electrical polarity and stimulated H⁺ extrusion. Previous investigations have shown that Al³⁺ decreases solute leakage at low _pH and that the alleviation of H⁺ toxicity by cations appears to be a general phenomenon with effectiveness dependent upon charge (C³⁺>C²⁺>C^l+). Alleviation of one cation toxicity by another toxic cation appears to be reciprocal so that Al³⁺ toxicity is relieved by H⁺. It has been argued previously that this latter phenomenon accounts for the apparent toxicity of ALOH²⁺ and Al(OH)⁺₂. Reduction of cell-surface electrical potential by the ameliorative cation may reduce the cell-surface activity of the toxic cation.     

Effect of various metal ions on growth of two wheat lines known to differ in aluminium tolerance

The effects of aluminium (Al), manganese (Mn), zinc (Zn), copper (Cu), boron (B), iron (Fe), gallium (Ga), scandium (Sc) and lanthanum (La) on growth of an Al-tolerant and an Al-sensitive line of wheat (Triticum aestivum L.) were measured in solution culture. The concentrations of nutrients in the basal nutrient solution were (M) 500 Ca, 100 Mg, 300 K, 600 N (150 NH₄, 450 NO₃), 600 SO₄, 2.5 P, 3 B, 2.5 Fe, 0.5 Zn, 0.5 Mn, 0.1 Cu at a pH of 4.7. The major solution nutrient concentrations were maintained at the nominal concentration with monitoring, frequent additions and weekly renewal. Differentiation in yield between the Al-tolerant and Al-sensitive line only occurred in the presence of Al indicating that, in the long term, none of the other metals tested could be used as an analog for Al. The visual symptoms in the roots of Cu toxicity (in both lines) and Al toxicity (in the sensitive line) were similar. The solution concentration (M) at which yield of the roots of the tolerant line was reduced by 50% was, in order of increasing tolerance, Cu 0.5, Sc 1.1, La 7.1, Ga 8.6, Al 15, Zn 19, Fe 84, B 490 and Mn 600.     

The control of boron accumulation by two genotypes of wheat

The mechanism of boron (B) uptake in wheat was studied using two genotypes with known differences in their ability to accumulate B. Influx and efflux of B was measured in the roots of intact 21 d old plants.Roots grown in 15 M B, when transferred to solutions containing 1mM B showed a rapid increase in B content for up to 60 min, after which no further increase was evident up to 4 h. No genotypic difference in B influx was apparent over these time periods. Roots grown in 1mM B for 7 d and then rinsed in B-free solutions quickly lost most of B that they contained within 1 hour; little further efflux was observed over the following three hours. As with the influx, no genotypic difference in B flux was evident.It is suggested that the lack of genotypic difference in the short-term B fluxes could be due to a masking effect of extracellular B bound in the cell walls of the roots.Department of Botany, University of Adelaide     

The genetic characterisation of novel multi-addition doubled haploid lines derived from triticale x wheat hybrids

Two novel 46-chromosome doubled haploid lines, W66 and M17, derived from separate hexaploid triticale x bread wheat crosses, were characterised using cytological and biochemical markers. Both lines were shown to be relatively stable cytologically, over 11 and 8 generations of selfing, respectively. By examining mitotic and meiotic chromosomes, the stabilities of the two lines were shown to be similar with frequencies of 2n=46 in 74.2–85.5% of cells. However, over selfed generations, the rye chromosomes were shown to have lost some of their heterochromatin, which made it difficult to establish their continued presence using cytological techniques, such as C-banding alone. Cytological evidence from pairing studies, C-banding, and fluorescence in-situ hybridization, showed that both M17 and W66 are wheat/rye multi-addition lines with rye chromosome constitutions of 1R+6R, and 1R+4R, respectively. These conclusions were confirmed by isozyme and storage-protein analysis.