The Influence of Genes for Vernalization Response on Development and Growth in Wheat

Studies were made of the influence of genes for vernalizationresponse on the growth and development of four near-isogeniclines of bread wheat (Triticum aestivum L.). The duration from sowing of flower initiation, terminal spikeletformation and ear emergence all increased with increasing vernalizationresponse. There was a close positive relationship between thedays from sowing to flower initiation and from sowing to earemergence, indicating that the duration of either phase of developmentis a useful measure of relative vernalization when daylengthdoes not limit the rate of development. Total spikelet number per ear and the duration of spikelet initationincreased with increasing vernalization response and there wasa correspondingly higher rate of spikelet initiation in thetwo lines with stronger vernalization response. Most of the differences in growth between the lines were associatedwith diferences in development caused by the vrn genes. Maximumtotal above-ground dry matter and total leaf area per plantincreased with increasing vernalization repsonse but relativegrowth rate and leaf area per plant were not significantly differentbetween the lines. There were no differences in net assimilationrate between the four lines until 40 d from sowing; thereafterit decreased, with the greatest decrease in the line with thestrongest vernalization response. Flower initiation, terminal spikelet formation, spikelet initiation, ear emergence, growth rate     

Relationships between photosynthetic area and other growth attributes with grain yield in 6- and 2-row barley genotypes

Six-row and 2-row barley genotypes were grown as individually spaced plants in the field, and estimates of area of green tissue and other characters were obtained at ear emergence and maturity. Positive correlations (P<0.01) were found within both 6- and 2-row types between grain dry wt per main culm and grain number, mean date of ear emergence, area of green tissue above the flag-leaf node, and dry wt of the third leaf below the ear (F-2 leaf). This supports the hypothesis that the magnitude of assimilate supply prior to anthesis is a very important determinant of grain yield in barley, and the possible use of the F-2 leaf as a criterion for selection of genotypes with a large photosynthetic capacity and grain yield is discussed.     

Studies in the Diagnosis of Mineral Deficiency

Material from four fertilizer trials on barley in Hampshire was analysed with the principal purpose of comparing the extent to which the potassium content of different plant organs was diagnostic of potassium deficiency. Samples of older leaf blades and sheaths, young leaves, stems and ears were gathered at the time of ear emergence from each of the 108 plots, and analysed spectrographically for calcium, iron, magnesium, manganese, potassium and sodium.
Differences in composition between plants from the different sites were proportionately greater in the older leaf blades than in the other organs for calcium, the young leaves for manganese and sodium, and the older leaf blades and sheaths for potassium. Differences in sodium and manganese content at the different sites appeared to be related to the differences in potassium status.
Applications of muriate of potash increased the potassium content of all organs except the ears, and decreased the content of magnesium, manganese and sodium, and of iron at one site. The effect of potassium supply on manganese and sodium content was most marked in the young leaves. The proportional increases observed in potassium content as a result of application of muriate of potash were similar at all four sites, in spite of the fact that responses in growth and yield differed greatly.
As between the four sites, the responses to muriate of potash observed in the yields of grain are significantly correlated with the potassium content of the older leaf blades and the stems, and the following tentative limiting values are put forward, above which no increase in grain yield as a result of potassic manuring may be expected:
(a) in the older leaf blades at the time of ear emergence 0.92% potassium in dry matter, (b) in the stems at the time of ear emergence 1–01 % potassium in dry matter.     

Effect of climatic zones and sowing dates on maize emergence and leaf parameters

Variability in climate context is causing direct effects on reducing crops production. Possible strategies to counteract the impact of climate change is to configure the sowing time of crops and to seek out crop cultivars that are adapted to extreme climatic conditions of a specific ecological zone. Experiments were conducted at three ecological zones of Khyber Pakhtunkhwa Province of Pakistan i.e. (i. Agronomy Research Farm, The University Agriculture Peshawar ii. Agriculture Research Institute, Mingora, Swat iii. Farmers field, Karak, during the summer season, 2017–2018). Experiment was laid-out in Randomized Complete Block Design with split plot arrangement having four replications. Maize cultivars i.e. local open pollinated varieties (Azam, Jalal) and two hybrids (CS-200, CS-220) were sown on different dates starting from May 25 to July 25 with twenty days interval. Analysis of the data showed that early sowing (25th May) of maize in all zones (Karak, Peshawar and Swat) resulted in maximm emergence m⁻², early emergence, highest leaf area, leaf area index, maximum light interception and higher chlorophyll content. However, delay in sowing time from 15th June onward in all zones resulted in lower emergence m⁻², delay in emergence, reduced leaf area, leaf area index, lower light interception and chlorophyll content. Maize hybrids (CS-200 and CS-220) exhibited maximum emergence m⁻², days to emergence, leaf area, chlorophyll content and light interception. At all zones (Karak, Peshawar and Swat) early sowing of maize hybrids (25th May to 15th June) is recommended for maintaining proper emergence parameters and improved leaf configuration for efficient resources utilization.     

东北草原羊草种群单穗数量性状的生态可塑性

羊草（Leymus chinensis(Trin.)Tzvel.）是一种多年生禾本科优良牧草。经过对东北草原3个固定样地连续12a,分别随机取样100个穗状花序的调查和测定,将羊草种群单穗数量性状的生态可塑性进行了统计分析,并且分别与不同生长发育阶段气候因子进行了相关分析。结果表明,羊草种群的单穗长度、小穗数和小花数的生态可塑性变化在样地内和样地间,以及年度内和年度间均达到了极显著水平。其中,均表现为年度内大于年度间,样地内大于样地间,样地间大于年度间。羊草种群单穗数量性状均与形成性状的生育期,及其以前各生育期不同阶段的光照时间、积温、降水量有着一定程度的相关关系。在整个冬性枝条生长发育期,较多的降水、较少的光照时间和较低的积温将对翌年幼穗分化及其生长有一定的促进作用,而较少的降水、较多的光照时间和较高的积温则有不利影响;从拔节到抽穗阶段较多的降水对幼穗分化具有一定的促进作用,但从返青到抽穗不同阶段较高的积温和较多的光照、以及返青初期较多的降水量则有着一定的不利影响。气候因子对羊草种群幼穗分化滞后效应的生态时间差可长达10个月。     

Photosynthesis and transpiration of the flag leaf in four spring-wheat cultivars

Co₂ exchange and transpiration rates of the flag leaves of four spring wheat (Triticum aestivum L.) cultivars, namely Glenlea, Neepawa, Opal and Kolibri, were compared using infra-red gas-analysis technique. The plants were grown in a controlled environment under an 18-h photoperiod, with day and night temperatures of 20 and 15° C, respectively. The time course of the CO₂-exchange rate (CER) of the flag leaf differed among cultivars. CER began to decrease rapidly some 2 weeks after ear emergence in Glenlea, Neepawa and Kolibri, but only after 4 weeks in Opal. The decline in CER of Glenlea, Neepawa and Opal was continuous throughout the period of grain development whereas in Kolibri CER was maintained at a constant level between the 4th and 6th weeks after ear emergence. The transpiration rates of the flag leaves of the 4 cultivars did not change markedly until 6–7 weeks after ear emergence, indicating that the reduction in CER was not primarily a response to increased stomatal resistance to the diffusion of CO₂. Removing the ear of the main shoot of intact plants failed to depress CER of the subtending flag leaf until 5 weeks after ear removal. Removing the ears of all the tillers of plants in which all but 3 tillers had been removed at ear emergence did not depress CER until 4 weeks after ear emergence, but removal of the ear of the main shoot of plants where all the tillers had been removed at ear emergence reduced the CER of the flag leaf 2 weeks after ear removal. Removal of tillers at ear emergence had a marked effect on the time course of CER and transpiration rates of the flag leaf. Both CER and transpiration rates of a 4-tiller plant were maintained at a higher level throughout ear development as compared to those of a one-tiller plant. The transpiration rate of the flag leaf of Glenlea increased during the later part of the life of the leaf even for one-tiller plants with no ear, indicating that such a stomatal response may be part of the normal course of leaf aging and not a response to a feedback stimulus from the ear.     

Survival of Tillers and Distribution of Dry Matter between Ear and Shoot of Barley Varieties

Plants of Plumage Archer barley grown in pots produced moreshoots than did Proctor, but had fewer ears at maturity, becausesome shoots died about 7 days before ear emergence. The numberand position on the plant of the shoots that died were consistentfor particular growing conditions. Shoots that died were notalways the last to be produced. There were no consistent differencesin dry weight, leaf area, nitrogen content, or apex developmentbetween shoots that did and did not survive; nor did removingthree developing ears on older shoots affect the survival ofother shoots. Growth of Plumage Archer plants was not checkedby death of shoots; dry matter, nitrogen, and leaf area wereredistributed so that increase in surviving shoots compensatedfor losses in the dead shoots. The dry-weight ratio of ear to shoot was smaller for Proctorthan for Plumage Archer at ear emergence and anthesis, but atmaturity it was greater for Proctor, both when ears were shadedto prevent them photosynthesizing and when they were unshaded.The varietal difference in ear: shoot dry-weight ratio was reversedbecause the relative growth-rate of ears of Proctor was greaterand because more dry matter was lost from its shoots. Both changesmay have been caused by translocation to the ear of a greaterproportion of the assimilate from the shoots of Proctor thanof Plumage Archer. Leaves of Proctor appeared to be more efficientin producing dry matter for the ear than those of Plumage Archer.     

长苞铁杉幼苗在林窗不同位置的建立

通过2003年12月到2005年1月对福建省天宝岩国家级自然保护区长苞铁杉林内椭圆形林窗(面积118m2)中心、中部、边缘和林下样地进行种子埋藏及幼苗定位观测实验,研究了长苞铁杉幼苗在林窗不同位置中的建立。结果表明:在林窗内不同位置对长苞铁杉幼苗建立有显著影响。林窗中心样地、林窗中部样地、林窗边缘和林下样地内长苞铁杉幼苗发生率分别为10%,10.7%,6%和6%。从林冠下到林窗中心,长苞铁杉种子的幼苗发生率略有增高趋势。在林窗中心样地和林窗中部样地中雨水冲刷是幼苗死亡的最主要原因,而在林窗边缘样地和林下样地中昆虫的取食是幼苗死亡的最主要原因。林窗位置对幼苗的存活率有显著影响,林窗中部样地幼苗存活率最高(11.4%),林窗中心样地幼苗存活率次之(6.7%),而林窗边缘样地和林下样地幼苗则均全部死亡。种子营养消耗完后,在林窗中心、林窗中部、林窗边缘和林下等4个位置样地中,林窗中心样地幼苗平均高度最高。经过一个生长季后,林窗中心样地中幼苗的根生物量、茎生物量和总生物量均略高于林窗中部样地的幼苗,但差异并不显著。林窗中心样地幼苗叶生物量、叶重比、叶/地上等指标显著高于林窗中部样地的幼苗,而茎重比则低于林窗中部样地的幼苗。     

Spread of potato leafroll virus is decreased from plants of potato clones in which virus accumulation is restricted

Tubers of eight potato clones infected with potato leafroll luteovirus (PLRV) were planted as ‘infectors’ in a field crop grown, at Invergowrie, of virus-free potato cv. Maris Piper in 1989. The mean PLRV contents of the infector clones, determined by enzyme-linked immunosorbent assay (ELISA) of leaf tissue, ranged from c. 65 to 2400 ng/g leaf. Myzus persicae colonised the crop shortly after shoot emergence in late May and established large populations on all plants, exceeding 2000/plant by 27 June. Aphid infestations were controlled on 30 June by insecticide sprays. Aphid-borne spread of PLRV from plants of the infector clones was assessed in August by ELISA of foliage samples from the neighbouring Maris Piper ‘receptors’. Up to 89% infection occurred in receptor plots containing infector clones with high concentrations of PLRV. Spread was least (as little as 6%) in plots containing infectors in which PLRV concentrations were low. Primary PLRV infection in guard areas of the crop away from infectors was 4%. Some receptor plants became infected where no leaf contact was established with the infectors, suggesting that some virus spread may have been initiated by aphids walking across the soil.     

南京地区落叶栎林主要木本植物的展叶动态研究

 植物的展叶过程是由自身遗传因子决定的,同时又受到多种生态因子的调节,反映了植物的生活史对策和群落物种多样性的维持机制。在2001和2002年的3～6月间,不定期记录了南京地区三个落叶栎(Quercus spp.)林中主要木本植物的展叶情况,包括被标记标准枝的叶数、叶的长度、宽度、叶面积、叶干重等参数。结果表明在所调查的落叶栎林中,林冠层物种的成熟叶面积和单位叶面积干重都显著大于林下层物种;最早展叶的物种为林下层物种,但林冠层展叶顺序与林下层无显著差异。叶面积越大、单位叶面积干重越小的物种展叶越晚;林冠层物种展叶较林下层快,物种成熟叶面积越大,展叶速率越大。最后对展叶顺序和展叶速度的生态学意义作了讨论。     

Influence of potassium and sodium nutrition on leaf area components in Eucalyptus grandis trees

Background and Aims

Recent studies showed a positive tree response to Na addition in K-depleted tropical soils. Our study aimed to gain insight into the effects of K and Na fertilizations on leaf area components for a widely planted tree species.

Methods

Leaf expansion rates, as well as nutrient, polyol and soluble sugar concentrations, were measured from emergence to abscission of tagged leaves in 1-year-old Eucalyptus grandis plantations. Leaf cell size and water status parameters were compared 1 and 2 months after leaf emergence in plots with KCl application (+K), NaCl application (+Na) and control plots (C).

Results

K and Na applications enhanced tree leaf area by increasing both leaf longevity and the mean area of individual leaves. Higher cell turgor in treatments +K and +Na than in the C treatment resulting from higher concentrations of osmotica contributed to increasing both palisade cell diameters and the size of fully expanded leaves.

Conclusions

Intermediate total tree leaf area in treatment +Na compared to treatments C and +K might result from the capacity of Na to substitute K in osmoregulatory functions, whereas it seemed unable to accomplish other important K functions that contribute to delaying leaf senescence.     

Analysis of Growth and Yield of Winter and Spring Wheats

In a field experiment to investigate the physiological causesof variation in yield between autumn- and spring-sown wheatand between old and new varieties, the grain yields of the winterwheats were 3-15 per cent, greater than of the spring ones andthe new varieties Cappelle-Desprez and Jufy I yielded 40-70per cent, more than Squarehead's Master and Atle. Nitrogen fertilizerincreased the yields of Cappelle-Desprez and Jufy I more thanof Atle, and decreased the yield of Squarehead's Master by makingit lodge. Until ear emergence the winter varieties had greater leaf-areaindices (L) and dry weights, but smaller net assimilation rates(E), than the spring varieties. Square-head's Master had greaterL but smaller E, and similar dry weight to Cappelle-Desprez.Jufy I had similar E to Atlc, but greater L and dry weight.Nitrogen increased L and dry weight, but decreased E. All thedifferences in E between varieties and nitrogen treatments couldbe explained by the opposite effects on L, that is to say, thedifferences in E were caused by variation in mutual shadingarising from the differences in L and not by changes in leafphysiology. L of winter wheat reached its maximum at the end of May, butL of spring wheat continued to increase until ear emergence.Afterwards Ldecreased more rapidly for winter than for springwheat, so that eventually spring wheat had the greater L. Thesedifferences in the time changes of L partially compensated forthe shorter growth period of spring wheat, and tended to equalizethe grain yield from winter and spring sowings. After ear emergence total dry weight of winter varieties continuedto be greater than of spring ones, but the difference in dryweight of ears was much smaller because ear: shoot dry-weightratio was greater for the spring varieties. Total dry weight,ear dry weight and ear: shoot ratio were all greater in thenew than in the old varieties. Leaf area duration (D) afterear emergence was slightly greater for the winter than for thespring varieties and similar for old and new. The apparent efficiencyof this leaf area in grain production, measured by the grainleaf ratio (ratio of grain dry weight to D), was similar forwinter and spring varieties but greater for new than for old.This suggests that Cappelle-Desprez and Jufy I have higher grainyields because their ears photosynthesize more than do the earsof Squarehead's Master and Atle. Before ear emergence winter varieties had more shoots than springones, and old varieties more than new. After ear emergence therewere only small differences in numbers of ears; percentage survivalwas greater for spring than for winter and for new than forold varieties. Differences in dry weight between varieties were not causedby differences in nitrogen uptake.     

Elevated CO2 concentration enhances the role of the ear to the flag leaf in determining grain yield of wheat

Net photosynthetic rate (P _N) of ear and flag leaf during grain filling stage and grain yield of plants with non-darkened or darkened flag leaf or darkened ear were examined in two different CO₂ concentrations: ambient (AC) and AC+200 μmol mol⁻¹ (EC). Ear showed much higher enhancement (56 %) of P _N than flag leaf (23 %) under EC. Moreover, CO₂ enrichment shortened the photosynthetic duration of flag leaf relative to ear. In this way the ratio of ear to flag leaf contribution to grain yield increased from 1.18 (AC) to 1.39 (EC).     

浙江天童国家森林公园5种常绿阔叶植物的一次和二次抽枝进程

中国东部亚热带常绿阔叶林中, 部分常绿木本物种具有明显的二次抽枝现象, 即在春天完成第一次抽枝, 间隔一定的时间后又开始新一轮抽枝。但是关于这些植物第二次抽枝的进程, 迄今鲜有报道, 限制了人们对这些植物生活史对策的理解。该文以浙江天童常绿阔叶林中有二次抽枝的5种植物光叶山矾(Symplocos lancifolia)、檵木(Loropetalum chinense)、窄基红褐柃(Eurya rubiginosa var. attenuata)、杨梅(Myrica rubra)和栲树(Castanopsis fargesii)为研究对象, 调查并比较了第一次抽枝和第二次抽枝在昆虫取食压力、展叶动态和小枝投资大小3个方面的差异, 探讨第二次抽枝动态的主要特点。结果表明: 1)昆虫取食压力上, 杨梅、栲树2种植物第二次抽枝的叶片虫食率显著高于第一次抽枝, 光叶山矾、檵木和窄基红褐柃3种植物第一、二次抽枝的叶片虫食率没有差异; 2)在现叶速率(叶片数量的增加速率)上, 同一物种第一、二次抽枝的叶片数量增长模式相同, 光叶山矾、檵木、窄基红褐柃和杨梅4个物种呈持续式增长, 栲树则呈爆发式增长, 但是完成现叶所需时间并不完全相同, 光叶山矾、窄基红褐柃和杨梅第二次抽枝完成现叶比第一次少6-9天, 檵木和栲树第一、二次抽枝完成现叶所需时间则无差异; 3)在展叶速率上, 光叶山矾、檵木和窄基红褐柃第二次抽枝显著高于第一次抽枝, 但第一次抽枝较晚的杨梅和栲树第一、二次抽枝之间没有差异; 4)调查的5种植物, 第二次抽枝的投资总量均小于第一次抽枝, 光叶山矾、窄基红褐柃、杨梅和栲树4种植物, 第二次抽枝形成的小枝在叶片数量、单叶面积、小枝长度和小枝直径上都显著小于第一次抽枝, 檵木第二次抽枝形成的小枝在叶片数量和小枝长度上没有差异, 单叶面积和小枝直径则显著小于第一次抽枝。总体上看, 所研究物种第二次抽枝中的叶片虫食率、现叶速率和展叶速率都不小于第一次抽枝, 而第二次抽枝小枝投资总量较小, 这些可能是物种对相对较大的昆虫取食压力和即将来临的冬天不利条件等的适应。     

Grain Yield in Two Contrasting Varieties of Spring Wheat

To investigate factors determining grain yield in spring wheattwo contrasting varieties of high (Jufy I) and low (Peko) yieldingcapacity were grown in field and glasshouse experiments. In a field trial Jufy I yielded approximately 14 per cent moregrain than Peko on both control and nitrogen-treated plots.In another field trial employing small plots, although for bothvarieties doubling the seed-rate did not affect grain yield,the two varieties differed in their response to the increasein density. In Peko the yield level remained unaffected becausedoubling the seed-rate halved the number of fertile tillersper plant, whereas for Jufy I in addition to a shift in tillernumber per plant there were changes in the number of grainsper ear. In both varieties the weight per seed remained constant. When the two varieties were grown alone or as a 1: 1 mixtureat the same seed-rate the grain yields were similar. In themixture, Peko, compared with Jufy I, produced a greater numberof fertile tillers and consequently a greater contribution tothe total grain yield. In glasshouse experiments the grain yield per tiller and theorder of leaf area duration per tiller for the period from earemergence to grain ripening were both higher for Jufy I. Onthe other hand, there was no varietal difference for the netassimilation rate estimated during the vegetative phase, butexcluding the roots. Additional nitrogen primarily stimulated tiller production inboth varieties. Shading either the upper or lower parts of the plant demonstratedthat the ear and flag leaf and its sheath are important sourcesof assimilates for grain formation, whereas the lower partsare relatively unimportant in this respect. There were indicationsthat the response between varieties differed.     

Physiological Causes of Differences in Grain Yield between Varieties of Barley

In a field experiment on barley at Rothamsted with the highmean yield of 49 cwt. of grain per acre, the varieties Proctorand Herta produced 10—15 per cent, more grain than Plumage-Archeron plots that received no nitrogenous fertilizer. When nitrogenwas applied the difference was increased to about 30 per cent.,because the higher nitrogen supply caused the Plumage-Archercrop to lodge and did not increase its yield, while Proctorand Herta remained standing. The three varieties did not differ in leaf-area index nor innet assimilation rate before ear emergence, so that all hadthe same total dry weight. After ear emergence, the leaf-areaindices of Proctor and Plumage-Archer were nearly equal, butthat of Herta was smaller. Assuming that the photosyntheticefficiency of the leaves continued to be the same in all varieties,the higher grain yields of Proctor and Herta cannot be attributedto greater production of dry matter by the leaves, either beforeor after ear emergence. A pot experiment on plants with shadedears confirmed that the dry matter contributed to grain yieldby unit leaf area was nearly equal in all the varieties. The higher grain yield of Proctor and Herta than of Plumage-Archermust therefore have come from additional photosynthesis in partsof the plant other than the leaves, i.e. in the ears themselves.An attempt to demonstrate this directly in a pot experiment,by comparing the grain yields of plants with shaded or withunshaded ears, was unsuccessful because the varieties behaveddifferently in pots; Proctor and Herta produced only about 6per cent, more grain yield than Plumage-Archer, and though thedecrease in grain yield by shading the ears was slightly greaterfor Proctor and Herta, the differences were not significant. The sum of ear sizes (estimated from length and breadth measurements)per m.1 in the field experiment was greater for Proctor andHerta than for Plumage-Archer. Also the distribution of drymatter between developing ears and shoots apparently differedwith variety, so that at ear emergence the dry weight of earsper m.² was greater in the two higher yielding varieties. Theincreased amount of photosynthetic tissue in the ears of Proctorand Herta, as measured by size or weight, may not wholly explaintheir greater dry-matter production; ears of Herta may alsohave a higher photosynthetic efficiency. No differences in nutrient uptake that could account for thevarietal differences in grain yield were found. Plumage-Archerabsorbed more potassium, and Herta less phosphorus than theother varieties. About a quarter of the final content of nitrogen,and a third of the phosphorus, was absorbed after ear emergence,but the potassium content was nearly maximal at ear emergenceand later decreased. The pot experiment showed that, on the average of all varieties,26 per cent. of the dry matter in the grain at harvest originatedfrom photosynthesis in the ears, including 10 per cent, fromthe awns; 59 per cent, came from photosynthesis in the flag-leaflamina and sheath and peduncle, and 15 per cent, from partsof the shoot below the flag leaf.     

Powdery mildew of tabacco (Erysiphe cichoracearum DC.)

The natural spread of Erysiphe cichoracearum was assessed weekly on alternate leaves of irrigated and non-irrigated tobacco plants of Kutsaga 51 variety, grown in field plots in 1962-63. Leaf area, air temperature and humidity within the plots, relative turgidity of the leaves and soil moisture were also measured. Leaves emerged over a period of 37 days. A minimum of 29 days elapsed between leaf emergence and infection; irrigation lengthened this period by 2–6 days for leaves 2–6 and shortened it by 2–10 days for leaves 10–18. The duration of the initial resistant phase, in leaves at comparable stalk positions, appeared to be directly proportional to the eventual size of the leaves at reaping. Leaves were not infected until they were almost fully expanded. The longest dry period, when most irrigation water was applied, occurred when most lower leaves (2–8) were fully expanded and already infected; upper leaves (10–18)w ere then still expanding and not yet infected. Irrigation increased infection in all leaves; it increased the growth of the pathogen during dry weather and the subsequent susceptibility of leaves that were still actively expanding but not yet infected. Irrigation increased the percentage of susceptible leaf area infected, of intact plants, threefold and that of topped plants ninefold. Topped plants had less infection than intact ones.     

Boron accumulation and partitioning in wheat cultivars with contrasting tolerance to boron deficiency

Two pot experiments at the Plant Environment Laboratory (PEL), Reading, UK investigated sterility, boron (B) accumulation and B partitioning of wheat cultivars grown with limited B in the growing medium. The first experiment evaluated nine cultivars of spring wheat with diverse field responses to low available soil B, supplied with or without 20 μM B. A second experiment examined the response of a susceptible (SW-41) and a tolerant (Fang-60) cultivar to B-deficiency. These cultivars were supplied with either 20 μM B from sowing to flag leaf emergence and no added B thereafter, or 20 μM B from sowing to maturity. When B was not supplied in the nutrient solution, the number of grains ranged from 4 per ear (cv. BL-1135) to 32 per ear (cv. BL-1249) and sterility of competent florets ranged from 39% to 93%. Boron concentration in the flag leaf at anthesis did not differ greatly when the growing medium contained limited B, but differences between cultivars were evident when B was unlimited. Tolerance of B-deficiency was not related to the B concentration in the flag leaf. Some cultivars produced viable pollen and set grains while others failed to do so at similar B concentrations in the flag leaf. The two contrasting cultivars did not differ much in their pattern of B partitioning when B supply was restricted from flag leaf emergence onwards. Similarly, little evidence was found that the tolerant cultivars translocated B from their leaves, roots or stems when the supply in the growing medium was restricted. The proportion of total B partitioned in different organs was the same irrespective of B supply and cultivar. On average, leaves contained 68% of the total B content in the whole plant compared to 16% in the roots, 10% in the ears and only 6% in the stems. Tolerant or susceptible cultivars of wheat could not be distinguished based on the B concentration and B content of the flag leaf. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ethirimol-sensitivity in populations of Erysiphe graminis from plots of spring barley

Barley plots, cv. Proctor were sown with either ethirimol-treated or untreated seed. At seedling emergence, plots were inoculated with isolates of Erysiphe graminis either sensitive or insensitive to ethirimol, or left uninoculated. Mildew samples taken from the coleoptile leaves of seedlings, and later from leaf 6 (next but one to the flag leaf) were compared for ethirimol sensitivity using probit analysis. Probit lines were derived using ‘Wadley's analysis’. This analysis uses the number of survivors to estimate the total number of individuals originally present. In the test for ethirimol sensitivity a count of colonies on inoculated test leaves was taken to represent survivors. Microscopic counting of the original inoculum was thus avoided. The analyses snowed that the initial leaf inoculation treatments established mildew populations in the plots, which differed considerably in ethirimol sensitivity. Some 6 wk after inoculation the levels of sensitivity in these populations remained unchanged even though inoculum coming into the experiment from external sources was often much more insensitive than the mildew in some plots. Probit lines of response to ethirimol had shallow slopes, showing that large variability exists in the pathogen for this character.     

Experiments with CCC on wheat: effects of spacing, nitrogen and irrigation

In experiments with spring and winter wheat at Rothamsted and Woburn during 4 years CCC increased yield at close spacing (4 in) (10 cm) more than at usual spacing (8 in) (20 cm), but there was no interaction between spacing and yield. Some experiments tested up to 2·4 cwt/acre (300 kg/ha) N to see whether yields continued to increase with more than usual amounts of N, when CCC prevented lodging. There was no evidence of this. When a short dry spell occurred at ear emergence, yield of spring wheat was increased by 6 cwt/acre (750 kg/ha) by CCC and 10 cwt (1250 kg) by irrigation. CCC probably improves yield in these conditions because the larger root system it causes enables more ear-bearing shoots to survive. CCC increases yield in two ways, either by increasing ears or grain per ear. In an unlodged crop CCC usually makes the grains smaller, but by preventing lodging it can also increase size. Usually CCC decreases the leaf area per shoot. The flag leaf may be smaller, unchanged or larger than those of untreated plants. There was no obvious connexion between flag-leaf area and grain yield; when CCC decreased flag-leaf area duration by 25 %, grain yield was unchanged. The results suggest that using CCC gives a more than even chance of a profitable yield increase.