玻璃温室与田间栽培小麦幼穗分化的比较

以河南省大面积种植的弱春性品种"郑麦9023"及半冬性品种"周麦18"为材料,开展了玻璃温室和田间栽培条件下小麦幼穗分化进程的比较研究。结果表明,在小麦全生育期,玻璃温室内平均温度高于田间环境,小麦幼穗分化所需时间极显著低于田间环境(P < 0.01)。温度和0 ℃以上积温升高,小麦幼穗分化进程加快。与田间种植小麦相比,玻璃温室内小麦幼穗分化缩短的时期主要集中在分化前期(出苗-伸长期、单棱期、二棱期)。玻璃温室内小麦幼穗分化持续时间和总积温均随播期推迟而降低,幼穗分化各阶段出现时间亦随播期的推迟而后延。小麦幼穗分化进程存在品种间差异,其中"郑麦9023"幼穗分化持续时间小于"周麦18",各阶段出现的时间亦早于"周麦18"。温度对幼穗分化各时期的影响存在品种间差异。温度升高对"郑麦9023"幼穗分化中期(二棱期、护颖分化期、小花分化期)影响较大,对"周麦18"幼穗分化前期和后期(单棱期、二棱期、药隔分化期)影响较大。积温对"郑麦9023"护颖分化期和"周麦18"药隔分化期、二棱期影响较大。     

Early signs of disruption of wheat anther development associated with the induction of male sterility by meiotic-stage water deficit

 Water deficit during meiosis in microspore mother cells of wheat (Triticum aestivum L.) induces male sterility, which reduces grain yield. In plants stressed during meiosis and then re-watered, division of microspore mother cells seems to proceed normally, but subsequent pollen development is arrested. Stress-affected anthers generally lack starch. We employed light microscopy in conjunction with histochemistry to compare the developmental anatomy of water-stress-affected and normal anthers. The earliest effects of stress, detectable between meiosis and young microspore stages, were the degeneration of meiocytes, loss of orientation of the reproductive cells, and abnormal vacuolization of tapetal cells. Other effects observed during subsequent developmental stages were deposition of starch in the connective tissue where it is normally not present, hypertrophy of the middle layer or endothecial cells, and deposition of sporopollenin-like substances in the anther loculus. The resulting pollen grains lacked both starch and intine. These results suggest that abnormal degeneration of the tapetum in water-stressed anthers coupled with a loss of orientation of the reproductive cells could be part of early events leading to abortion of microspores. Received: 19 July 1996 / Revision accepted: 6 November 1996     

GENESIS诱导小麦雄性不育性与花药组织呼吸关系的初步研究

对小麦小孢子发育的各个时期,经GENESIS处理的和未处理的植株花药的总呼吸活性(Vt)、细胞色素途径呼吸活性(ρ′Vcyt)和交替途径实际呼吸活性(ρValt)进行了比较研究,结果表明,在各时期,处理植株花药的Vt呼吸均低于未处理植株,尤以单核期最为明显;在小孢子减数分裂期、四分体期和单核期,处理小麦植株花药的ρ′Vcyt均明显降低,而在小孢子减数分裂期和四分体期ρValt出现明显升高。结论认为,由呼吸过程中电子传递途径运行的改变而造成处理植株花药呼吸代谢的紊乱,可能是GENESIS诱导小麦雄性不育发生的重要原因。     

Physiological response of wheat varieties to elevated atmospheric CO2 and low water supply levels

In the phytotron experiment, the effect of elevated atmospheric CO₂ (EC, 750 μmol mol^?1) on the drought tolerance was studied in two winter varieties (Mv Mambo, tolerant; Mv Regiment, moderately tolerant) and in one spring variety of wheat (Lona, sensitive to drought). Changes in net photosynthetic rate (P _N), stomatal conductance, transpiration, wateruse efficiency, effective quantum yield of photosystem II, and activities of glutathione reductase (GR), glutathione-Stransferase (GST), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were monitored during water withdrawal. Drought caused a faster decline of P _N at EC, leading to the lower assimilation rates under severe drought compared with ambient CO₂ (NC). In the sensitive variety, P _N remained high for a longer period at EC. The growth at EC resulted in a more relaxed activation level of the antioxidant enzyme system in all three varieties, with very low activities of GR, GST, APX, and POD. The similar, low values were due to decreases in the varieties which had higher ambient values. A parallel increase of CAT was, however, recorded in two varieties. As the decline in P _N was faster at EC under drought but there was no change in the rate of electron transport compared to NC values, a higher level of oxidative stress was induced. This triggered a more pronounced, general response in the antioxidant enzyme system at EC, leading to very high activities of APX, CAT, and GST in all three varieties. The results indicated that EC had generally favourable effects on the development and stress tolerance of plants, although bigger foliage made the plants more prone to the water loss. The relaxation of the defence mechanisms increased potentially the risk of damage due to the higher level of oxidative stress at EC under severe drought compared with NC.     

Field response of wheat to arbuscular mycorrhizal fungi and drought stress

Mycorrhizal plants often have greater tolerance to drought than nonmycorrhizal plants. This study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi inoculation on growth, grain yield and mineral acquisition of two winter wheat (Triticum aestivum L.) cultivars grown in the field under well-watered and water-stressed conditions. Wheat seeds were planted in furrows after treatment with or without the AM fungi Glomus mosseae or G. etunicatum. Roots were sampled at four growth stages (leaf, tillering, heading and grain-filling) to quantify AM fungi. There was negligible AM fungi colonization during winter months following seeding (leaf sampling in February), when soil temperature was low. During the spring, AM fungi colonization increased gradually. Mycorrhizal colonization was higher in well-watered plants colonized with AM fungi isolates than water-stressed plants. Plants inoculated with G. etunicatum generally had higher colonization than plants colonized with G. mosseae under both soil moisture conditions. Biomass and grain yields were higher in mycorrhizal than nonmycorrhizal plots irrespective of soil moisture, and G. etunicatum inoculated plants generally had higher biomass and grain yields than those colonized by G. mosseae under either soil moisture condition. The mycorrhizal plants had higher shoot P and Fe concentrations than nonmycorrhizal plants at all samplings regardless of soil moisture conditions. The improved growth, yield and nutrient uptake in wheat plants reported here demonstrate the potential of mycorrhizal inoculation to reduce the effects of drought stress on wheat grown under field conditions in semiarid areas of the world.     

春小麦对骤旱的响应特征及其阈值分析

与缓慢发展的干旱过程不同,骤旱具有发生速度快,短期内可致害的特点。目前,关于作物骤旱致害的临界阈值及其调控机制尚不清楚。以春小麦为供试作物,通过桶栽试验,模拟研究骤旱过程中小麦受旱致害的过程特征及其控制因素。结果发现,发生骤旱时土壤含水量下降呈先快后慢的变化趋势,叶片水分和叶水势则呈先慢后快的指数变化趋势。叶片光合生理指标对土壤水分的下降存在明显的阈值响应,且不同生理指标的阈值并不完全相同,其中净光合速率与表征叶片光合能力的指标（最大羧化速率）对土壤有效含水量的响应阈值为0.4,气孔导度和蒸腾速率对土壤有效含水量的响应阈值分别为0.5和0.4。而小麦光合生理指标对叶片水分和叶水势的阈值响应并不明显。同时依据各生理指标相关和通径分析结果得出,骤旱发生时引起小麦叶片净光合速率快速降低的主导因子为非气孔因素,而并不是以往作物受旱研究中的气孔因素。本研究结果有望丰富干旱影响认知,并可为科学应对干旱提供依据。     

Interaction of water supply and N in wheat

The purpose of this study was to investigate effects of N nutrition and water stress on stomatal behavior and CO₂ exchange rate in wheat (Triticum aestivum L. cv Olaf). Wheat plants were grown hydroponically with high (100 milligrams per liter) and low (10 milligrams per liter) N. When plants were 38 days old, a 24-day water stress cycle was begun. A gradual increase in nutrient solution osmotic pressure from 0.03 to 1.95 mega Pascals was achieved by incremental additions of PEG-6,000. Plants in both N treatments adjusted osmotically, although leaf water potential was consistently lower and relative water content greater for low N plants in the first half of the stress cycle. Leaf conductance of high N plants appeared greater than that of low N plants at high water potentials, but showed greater sensitivity to reductions in water potential as indicated by earlier stomatal closure during the stress cycle. The apparent greater stomatal sensitivity of high N plants was associated with a curvilinear relationship between leaf conductance and leaf water potential; low N plants exhibited more of a threshold response. Trends in [CO₂]_INT throughout the stress cycle indicated nonstomatal effects of water stress on CO₂ exchange rate were greater in high N plants. Although estimates of [CO₂]_INT were generally lower in high N plants, they were relatively insensitive to leaf water potential-induced changes in leaf conductance. In contrast, [CO₂]_INT of low N plants dropped concomitantly with leaf conductance at low leaf water potentials. Oxygen response of CO₂ exchange rate for both treatments was affected less by reductions in water potential than was CO₂ exchange rate at 2.5% O₂, suggesting that CO₂ assimilation capacity of the leaves was affected more by reductions in leaf water potential than were processes related to photorespiration.     

作物干旱指标对西北半干旱区春小麦缺水特征的反映

针对作物水分胁迫较为严重的西北半干旱区,应用CI301-PS光合作用仪对春小麦开花到乳熟期间的生理特征和环境因子进行了近1个月的观测, 并研究分析了3种作物干旱指标叶水势、作物水分胁迫指数以及气孔导度随时间变化和对气象因子的响应.发现干旱胁迫增加时,叶片水分减少,作物水分胁迫指数增大,叶水势降低,气孔导度有所减小.因此,气孔下腔的CO2浓度降低,作物净光合速率有所减小,不利于半干旱区小麦生物量的累积;三者相比,叶水势是反应西北半干旱区作物干旱最敏感的指标;受半干旱区逆湿现象的影响,9:00或之后一段时间观测叶水势和气孔导度对小麦等作物缺水状况反映得更客观.     

Growth,biomass allocation and water use efficiency of two wheat cultivars in a mediterranean environment; a pot experiment under field conditions

Plants of two bread wheat cultivars,Triticum aestivum L. Katya Al and Mexipak 65, were grown in pots during the crop season in the field in NW Syria, a region with a Mediterranean climate. The experiment involved two treatments. Control plants were well-watered throughout the experiment (watering to 0.22 g water g^–1 dry soil). In the second treatment, water was withheld from the plants until soil water content had decreased to 0.10 g water g^–1 dry soil, the level that was maintained thereafter. Water use was measured by weighing the pots, and growth by destructive sampling. Growth of Katya and Mexipak was similar. Mexipak had a lower (though not significant atp<0.05) plant water use efficiency (WUE_p) in both treatments due to higher rates of water loss. On a leaf area basis differences in water use were especially high since Mexipak had a smaller total leaf area. In spite of a smaller investment in photosynthesizing area, Mexipak achieved similar growth as Katya. Carbon isotope discrimination and organic nitrogen concentration (both higher for Mexipak) suggest that Mexipak accomplished higher mean net photosynthetic rates with a higher mean leaf diffusive conductance, higher intercellular carbon dioxide partial pressure, and possibly a greater investment in the photosynthetic apparatus compared to Katya. Differences in carbon isotope discrimination suggest a larger difference in average photosynthetic WUE (net photosynthesis/transpiration) than in plant WUE. This could indicate that loss of carbon in respiration was greater in Katya. Gas exchange measurements on the youngest fully expanded leaves showed only minor differences between the cultivars. It is hypothesized that Mexipak, with a smaller total leaf area, is able to maintain high leaf conductance and photosynthesis for a longer period of time during the day or during the life span of leaves.     

小麦T型细胞质雄性不育系与可育系叶片蛋白质双向电泳分析

利用育性恢复基因(Rf3)的近等基因系1031-1、S-165和1031-1与S-165之间的正交与反交,创建了四个实验品系(1031-1、S-165、不育品系、反交品系);采用改进的蛋白质聚丙烯酰胺凝胶双向电泳技术,从发育遗传学的角度,对小麦T型细胞质雄性不育和可育株旗叶表达的相关蛋白产物进行差异分析。通过对旗叶蛋白的双向电泳分析,发现4个品系有相近的蛋白质双向电泳图谱。没有相应穗中差异蛋白质的出现。从蛋白质水平上证实了不育基因与恢复基因表达具有器官特异性特征。     

Correlated response in male and female sterility to selection for pupa weight in Tribolium castaneum

Summary The correlated responses in male and female sterility to 50 generations of individual selection for pupa weight in Tribolium were analyzed. Two replicate lines (S-lines) were selected for heavier pupa weight and stabilizing selection for pupa weight was practiced in two replicate control lines (C-lines). There was close agreement between replicates in both sets of lines for direct and correlated responses. The rate of inbreeding has been constant for all lines (approximately 0.5% per generation).Regression of generation means for pupa weight on generation of selection indicated a significant linear regression in the direct response for both lines. The linear increases of 46 and 55 g. per generation in the S-lines accounted for 98% of the variation among generations and the linear decreases of 5 and 10 g. per generation in the C-lines accounted for 70–90% of the variation in the generation means.Maximum likelihood estimators were used to calculate the frequency of male and female sterility for each generation and line. Average sterility in the base population ranged from about 4 to 12% for both sexes. Polynomial regressions of percent sterility on generation of selection showed that quadratic and higher order regressions were occasionally significant but accounted for a relatively small fraction of the total variation. In the two S-line replicates, linear regression coefficients of percent sterility on generation number were 0.16±.09 and 0.20±.07 for males and 0.72±.08 and 0.54±.08 for females, suggesting a larger correlated response in female than in male sterility. In the C-lines, linear regression coefficients were 0.02±.08 and –.12±.05 for males in the two replicates and –.05±.05 and –.05±.05 for females. Estimates of realized genetic correlations between pupa weight and sterility in the S-lines ranged from 0.04 to 0.14 for males and from 0.14 to 0.37 for females when the heritability of sterility was allowed to take on values from 0.05 to 0.25.Supported by NSF Grants G-1238 and GB-5987, NIH Grant GM-16074 and NIH Fellowship 1 FO2 GM4 5130-01.     

Photosynthesis and conductance of spring wheat ears: field response to free-air CO2 enrichment and limitations in water and nitrogen supply

The mid-day responses of wheat ear CO₂ and water vapour exchange to full-season CO₂ enrichment were investigated using a Free-Air CO₂ Enrichment (FACE) apparatus. Spring wheat [Triticum aestivum (L). cv. Yecora Rojo] was grown in two experiments under ambient and elevated atmospheric CO₂ (C_a) concentrations (approximately 370 μ mol mol ^{− 1} and 550 μ mol mol ^{− 1}, respectively) combined first with two irrigation (Irr) schemes (Wet: 100% and Dry: 50% replacement of evapotranspiration) and then with two levels of nitrogen (N) fertilization (High: 350, Low: 70 kg ha ^{− 1} N). Blowers were used for C_a enrichment. Ambient C_a plots were exposed to blower induced winds as well the C_a × N but not in the C_a × Irr experiment. The net photosynthesis for the ears was increased by 58% and stomatal conductance (g_s) was decreased by 26% due to elevated C_a under ample water and N supply when blowers were applied to both C_a treatments. The use of blowers in the C_a-enriched plots only during the C_a × Irr experiment (blower effect) and Low N supply restricted the enhancement of net photosynthesis of the ear due to higher C_a. In the latter case, the increase of net photosynthesis of the ear amounted to 26%. The decrease in g_s caused by higher C_a was not affected by the blower effect and N treatment. The mid-day enhancement of net photosynthesis due to elevated C_a was higher for ears than for flag leaves and this effect was most pronounced under ample water and N supply. The contribution of ears to grain filling is therefore likely to increase in higher C_a environments in the future. In the comparison between Wet and Dry, the higher C_a did not alter the response of net photosynthesis of the ear and g_s to Irr. However, C_a enrichment increased the drought tolerance of net photosynthesis of the glume and delayed the increase of the awn portion of net photosynthesis of the ear during drought. Therefore, the role of awns for maintaining high net photosynthesis of the ear under drought may decrease when C_a increases.     

Photosynthetic and anatomical responses of Eucalyptus grandis leaves to potassium and sodium supply in a field experiment

Although vast areas in tropical regions have weathered soils with low potassium (K) levels, little is known about the effects of K supply on the photosynthetic physiology of trees. This study assessed the effects of K and sodium (Na) supply on the diffusional and biochemical limitations to photosynthesis in Eucalyptus grandis leaves. A field experiment comparing treatments receiving K (+K) or Na (+Na) with a control treatment (C) was set up in a K‐deficient soil. The net CO₂ assimilation rates were twice as high in +K and 1.6 times higher in +Na than in the C as a result of lower stomatal and mesophyll resistance to CO₂ diffusion and higher photosynthetic capacity. The starch content was higher and soluble sugar was lower in +K than in C and +Na, suggesting that K starvation disturbed carbon storage and transport. The specific leaf area, leaf thickness, parenchyma thickness, stomatal size and intercellular air spaces increased in +K and +Na compared to C. Nitrogen and chlorophyll concentrations were also higher in +K and +Na than in C. These results suggest a strong relationship between the K and Na supply to E. grandis trees and the functional and structural limitations to CO₂ assimilation rates.     

Co-limitation by nitrogen and water constrains allocation response to drought in deciduous and evergreen shrubs in a semi-arid ecosystem

Plant Ecology - Semi-arid regions worldwide are expected to experience reduced precipitation with future climate change, in addition to increased intensity of precipitation events, heightening the...     

The functional divergence of biomass partitioning,carbon gain and water use in Coffea canephora in response to the water supply: Implications for breeding aimed at improving drought tolerance

Robusta coffee (Coffea canephora) is widely cultivated in regions where water availability is the major environmental constraint affecting crop production. The functional divergence associated with biomass partitioning, carbon gain and water use in response to water supply was examined in 10 one-year-old clones of robusta coffee with varying degrees of drought tolerance. The plants were grown outdoors in 24 L pots and either irrigated or subjected to a four-month water deficit. Under conditions of ample irrigation, clones with superior water use ability (i.e., a higher water potential, transpiration rate, apparent hydraulic conductance and biomass partitioning into roots and a lower wood density) displayed enhanced carbon gains. In contrast, under drought conditions, clones that postponed dehydration via more conservative water use rates showed lower relative decreases in stomatal conductance, photosynthetic rates and biomass accumulation. Isotopic signatures (δ¹³C) might be useful for identifying clones with improved performance under drought conditions. Our results suggest that combining useful morphological and physiological traits facilitates the successful assessment of coffee clonal performance in response to drought at the seedling stage. This strategy may be valuable when exploring a large number of genotypes in coffee-breeding programs because it reduces the time and resource costs that would otherwise be wasted on potentially undesirable genotypes.     

Steady state levels of free radicals in tomato fruit exposed to drought and ozone stress in a field experiment

The influence of drought and elevated ozone levels on the free radical contents of fruit from tomato has been investigated by electron paramagnetic resonance (EPR) spectroscopy. Under water deficit no differences in the signal intensity were observed between drought-stressed and control fruits, or between different harvests, from the same variety, whereas a reduction in the stomatal conductance of leaves under water deficit indicated a physiological effect of the drought stress on plants. One of the varieties investigated (Lycopersicon esculentum cv. Kremser Perle) generally showed higher radical levels than the other two. For relatively short periods of stress (≤ 20 d), the free radical contents of fruits that had received moderate ozone exposure were significantly higher than in fruits grown in filtered chambers with charcoal filtered air. However, all fruits had similar free radical levels after ~25 d of ozone fumigation.