The response of sorghum and sunflower to short-term waterlogging

Summary The effect of waterlogging on sunflower and sorghum was investigated in relation to stage of development (sunflower-6-leaf, buds-visible, anthesis; sorghum-5-leaf, initiation, anthesis) and duration of waterlogging (3, 6 and 9 days) under glasshouse conditions. Additionally, the potential adaptation of the two crops was observed by waterlogging some plants at all three growth stages. With sunflower, leaf expansion and stem extension were inhibited by waterlogging at the 6-leaf and buds-visible stage although these effects did not always persist until maturity while, with anthesis waterlogging, rapid desiccation of leaves was observed. Yield was most affected by the anthesis waterlogging but no consistent effect on seed number or 1000 seed weight was recorded.Waterlogging sorghum plants suppressed normal tillering but had little effect on dry weight of the main stem. Late tillering was stimulated by waterlogging. Reductions in leaf area occurred at all stages of development in response to waterlogging with these effects being more marked at initiation. Similarly, yield was most reduced by the initiation waterlogging largely as a result of reduced seed number.In neither species was there a clear relationship between duration of waterlogging and subsequent reduction in growth and yield. With respect to yield, stage of development seemed to be of greater importance than the duration of waterlogging. The growth and yield of multiple-waterlogged sunflowers was less affected by the anthesis treatment than that in plants experiencing a single waterlogging, suggesting that some form of adaptation was induced. In contrast, no such response was seen in sorghum.     

The response of sorghum and sunflower to short-term waterlogging

Summary Sorghum and sunflower were waterlogged for nine days during the vegetative, floral initiation/buds-visible or anthesis stage of growth under glasshouse conditions to observe the effects on root growth and development. In addition, some plants were waterlogged at all three stages to observe any adaptations induced by waterlogging. The most marked effects occurred at the initiation/buds-visible stage where a 30% reduction in root length and a 40% reduction in root dry weight of sorghum occurred with comparable figures for sunflower being 50 and 60% respectively. Generally, sorghum roots had a higher porosity than sunflower which may contribute to its greater tolerance to waterlogging. The observed changes in root growth are discussed in relation to previously documented effects of waterlogging on growth of the two species and changes which occur in the soil environment.     

渍水对四川小麦生理性状及产量的影响

采用二因素裂区设计,连续2年（2011-2012和2012-2013年）以川麦104和内麦836为对象,在小麦苗期、拔节期、孕穗期、开花期分别进行35 d的渍水处理,研究渍水对四川小麦生长和产量形成的影响.结果表明： 苗期渍水减产最大,减产10%～15%,随渍水时期的后移,对产量的影响减小.苗期渍水降低了第3～6叶SPAD值、单株分蘖力和单株成穗数,降低了有效穗数、花后干物质积累量和成熟期干物质量.拔节期渍水降低了第4～7叶SPAD值,孕穗期渍水降低了倒4、倒3、倒2叶SPAD值,拔节期和孕穗期渍水导致花后旗叶SPAD值下降,渐增期灌浆速率（R₁）和平均灌浆速率（R_mean）下降,千粒重下降.开花期渍水对产量影响较小.表明苗期渍水是四川稻茬小麦渍害临界期.     

WATER RELATIONS OF WATER-STRESSED,SPLIT-ROOT C4 (SORGHUM BICOLOR; POACEAE) AND C3 (HELIANTHUS ANNUUS; ASTERACEAE) PLANTS

Sorghum [Sorghum bicolor (L.) Moench] and sunflower (Helianthus annuus L.) were grown in a greenhouse with roots divided between sand irrigated with nutrient solution (–0.097 MPa) or nutrient solution containing polyethylene glycol (PEG) (–0.570 MPa) to compare the effect of unequal root zone stress on plant water relations of a C₄ (sorghum) and a C₃ (sunflower) plant. Roots also were divided between two pots of sand irrigated only with nutrient solution (controls) or only with PEG in nutrient solution. In addition to plant water-status measurements, photosynthetic rate, growth (height, root, and shoot dry weights), and evolution of ethylene (a gaseous hormone indicative of stress) were measured. Under all three split-root treatments, sunflower had a lower leaf water potential and produced more ethylene than sorghum. Sunflower was able to survive the PEG stress if half of its root system was under nonstressed conditions. Sunflower with half its root system irrigated with PEG usually had values of leaf water potential, osmotic potential, stomatal resistance, transpiration rate, photosynthetic rate, ethylene evolution, height, and dry weights that were close to those of the control plants. Sunflower with all roots exposed to PEG was wilted severely. Sorghum was little affected by PEG stress applied either to half or all the root system. Growth of sorghum was the same under all treatments. Apparently because stomata of sorghum were more closed in the partial stress test than those of sunflower, sorghum conserved water and had a higher leaf water potential, which might have permitted growth with stress.     

Effect of waterlogging yam vines on vegetative growth and tuber yield

The effect of waterlogging the vines of two yam varieties for 24, 48 and 72 hours at two stages of growth, with or without fertiliser application, was studied in the field. Waterlogging caused a progressive degeneration of the leaf starting with the development of fresh lesions on the lower leaf surface, through necrotic spots or portions, to complete leaf necrosis. The degree of leaf damage was greater with Um 680 (Dioscorea alata) than with Obiaoturugo (D. rotundata). Waterlogging also caused the breakdown of the apical buds of the vines. The degree of damage increased with the duration of waterlogging. Younger plants suffered more damage than older plants, and plants treated with fertiliser suffered more than plants without fertiliser. Waterlogging ultimately hastened the final senescence of the yam vine. Waterlogging vines for 24 h had no effect on tuber yield, while waterlogging for 48 and 72 h reduced tuber yield by 32.4% and 43.2% respectively (P< 0.01). Waterlogging vines at the early growth stage produced 47.6% (P <0.01) less yield than waterlogging at a later stage. It is suggested that short-term or long-term waterlogging of the yam vine, or parts thereof, is the main cause of reduced leaf area and low yield in unstaked compared with staked yarn crops. Waterlogging may also be a predisposing factor to disease infection of yam vines by soil-borne micro-organisms.     

不同渍水时间对苗期和花期大豆生长及碳氮代谢的影响

以大豆品种南农99.6为材料,通过盆栽试验研究了苗期和花期渍水对大豆生长及碳氮代谢的影响.结果表明: 渍水显著抑制了大豆的生长,植株生物量、叶面积、叶片色素含量和光合速率均显著下降,而丙二醛(MDA)含量显著升高;随着渍水时间的延长,各生理指标的变化幅度增大;渍水胁迫解除后有一定的恢复,渍水10 d处理后恢复能力较渍水20 d处理强.可溶性碳、氮物质及关键酶对渍水反应不同,可溶性糖含量以及叶片谷氨酰胺合成酶和蔗糖合成酶的活性上升,而可溶性蛋白含量下降.渍水对苗期大豆植株生物量、叶面积和MDA含量的影响比花期小.苗期和花期渍水时间越短,大豆受到的伤害越小,其恢复能力也越强.渍水时间在10 d内,大豆植株能够通过自身的调节逐渐恢复.     

Nitrogen fertiliser rate and post-anthesis waterlogging effects on carbohydrate and nitrogen dynamics in wheat

Waterlogging is predicted to increase in both magnitude and frequency along with global warming, and will become one of the most severe adversities for crop production in many regions. Nitrogen is considered to be an effective up-regulatory nutrient for crops grown under stress and non-stress conditions. In this study, we try to evaluate N fertiliser effects on contents of carbohydrate and N dynamics, dry matter accumulation in shoot, yield under post-anthesis waterlogging. Waterlogging after anthesis significantly reduced grain yield due to decrease in thousand-kernel-weight and in grain number per spike. High N fertiliser application aggravated grain yield loss due to post-anthesis waterlogging. These yield losses were related to the decreases in dry matter accumulation, redistribution of stored photosynthate to the grain, and the conversion capacity from carbohydrate to starch in grain. The decrease in dry matter accumulation could be attributed to the reduced activities of Pn (photosynthesis) and SPS (sucrose phosphate synthase) in the flag leaf, while the low capacity in starch synthesis could be explained by the reduced activities of sucrose synthase (SS) and soluble starch synthase (SSS) in grain. Total N uptake in shoot was also reduced, which could contribute to the losses in biomass and yield by waterlogging. The decrease in Pn was inconsistent with the increase in N content in the flag leaf at high N fertiliser application under post-anthesis waterlogging.     

Stay‐green: A consequence of the balance between supply and demand for nitrogen during grain filling?

Retention of green leaf area in grain sorghum under post‐anthesis drought, known as stay‐green, is associated with greater biomass production, lodging resistance and yield. The stay‐green phenomenon can be examined at a cell, leaf, or whole plant level. At a cell level, the retention of chloroplast proteins such as LHCP2, OEC33 and Rubisco until late in senescence has been reported in sorghum containing the KS19 source of stay‐green, indicating that photosynthesis may be maintained for longer during senescence in these genotypes. At a leaf level, longevity of photosynthetic apparatus is intimately related to nitrogen (N) status. At a whole plant level, stay‐green can be viewed as a consequence of the balance between N demand by the grain and N supply during grain filling. To examine some of these concepts, nine hybrids varying in the B35 and KS19 sources of stay‐green were grown under a post‐anthesis water deficit. Genotypic variation in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen (SLN) and N uptake during grain filling. Matching N supply from age‐related senescence and N uptake during grain filling with grain N demand found that the shortfall in N supply for grain filling was greater in the senescent than stay‐green hybrids, resulting in more accelerated leaf senescence in the former. We hypothesise that increased N uptake by stay‐green hybrids is a result of greater biomass accumulation during grain filling in response to increased sink demand (higher grain numbers) which, in turn, is the result of increased radiation use efficiency and transpiration efficiency due to higher SLN. Delayed leaf senescence resulting from higher SLN should, in turn, allow more carbon and nitrogen to be allocated to the roots of stay‐green hybrids during grain filling, thereby maintaining a greater capacity to extract N from the soil compared with senescent hybrids.     

不同花生品种对旱涝胁迫的响应及生理机制

为评价花生对旱、涝胁迫的响应,本试验以4个旱、涝耐性差异明显的花生品种为材料,运用温室防雨盆栽方法,在苗期、花针期分别进行正常灌溉(对照)、干旱(7d,叶片萎蔫)、根部淹涝(土面水深2 cm,时间1d、3d、7d)和整株淹涝(水深至苗顶,时间1d、3d、7d)的处理,测定地上部及根系生物量、根冠比、根系活力、叶片超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量。结果表明,苗期、花针期干旱均抑制地上部生长,提高根冠比;苗期干旱降低根系生物量,而花针期增加。2个时期淹涝均促进地上部生长、抑制根系生长、降低根冠比,并随淹水加深、延时而加重。旱、涝条件下根系活力均降低,SOD、MDA呈上升趋势。遭受相同时间(7d)的水分胁迫后,危害程度以干旱重于淹涝,花针期重于苗期。基于生物量、生理指标变化的综合分析进一步表明,4个花生品种的旱、涝耐性差异很大,湘花55号耐旱性强、耐涝性弱,豫花15号耐旱性弱、耐涝性强,中花4号耐旱、涝性均最弱,中花8号耐旱、涝性均最强。     

花前渍水预处理对花后渍水逆境下扬麦9号籽粒产量和品质的影响

以扬麦9号为材料,研究花前渍水预处理对花后渍水逆境下小麦籽粒产量和品质的影响。结果表明,与未进行渍水预处理相比,花前渍水预处理提高了小麦植株对花后渍害的抗性,生物产量、收获指数和千粒重显著提高,进而显著提高了籽粒产量;花前渍水预处理显著提高花后氮素积累量及其对籽粒氮素的贡献率,降低了花前贮藏氮素运转量及其对籽粒氮素的贡献率,进而引起籽粒球蛋白含量提高,但显著降低了清蛋白、醇溶蛋白、谷蛋白和全蛋白质含量、以及干湿面筋含量和沉降值;花前渍水预处理还提高了籽粒直链淀粉和总淀粉含量和降落值,降低了支/直链淀粉比,显著提高了面粉峰值粘度、低谷粘度、崩解值、最终粘度、回冷值和峰值时间,但对糊化温度无显著影响。     

The development of waterlogging damage in wheat seedlings (Triticum aestivum L.)

Summary The effects of waterlogging on concentrations of gases and various solutes dissolved in the soil water were investigated in the laboratory, to determine whether the early disruption to the growth of wheat was most closely associated with depletion of dissolved oxygen, accumulation of toxins, or changes in concentrations of nutrient ions in the soil water. Waterlogging slowed shoot fresh weight accumulation, leaf extension and nodal root growth; it also caused death of the seminal root system and early senescence of the lower leaves. However, the shoot dry weight initially increased above that of the non-waterlogged controls, and thus was not a reliable indicator of the early restriction to plant growth and development. The symptoms of damage to shoots and roots were attributed to the fall in soil oxygen concentrations, rather than to any decrease in concentration of inorganic nutrients in the soil water, or to the accumulation of any other measured solutes to toxic concentrations.     

Changes in water status during water stress at different stages of development in wheat

The dynamics of stomatal resistance and osmotic adjustment in response to plant water deficits and stage of physiological development was studied in the leaves of spring wheat ( Triticum aestivum L., GWO 1809). Plants were germinated and grown in pots in a growth chamber at the Duke University Phytotron to four physiological stages of development (4th leaf, 7th leaf, anthesis, and soft dough), during which time stomatal resistance, total water potential and osmotic potential were measured on the last fully developed leaf of water stressed and non-stressed plants. Pressure potential was obtained by difference. Stomatal closure of the abaxial and adaxial surfaces were independent of each other, each having a different critical total water potential. The total water potential required to close the stomata on the last fully developed leaf were different at different stages of physiological development, decreasing as the plants grew older. The development of osmoregulation in wheat allows the closure of stomata during the vegetative stage at a high total water potential, but insures that stomata remain open from anthesis through the ear filling period to a lower total water potential.     

Effects of irradiation level on leaf growth of sunflower

Sunflower, Helianthus annuus L. cv. INRA 6501, plants were grown in a gravel culture subirrigated with Hoagland nutrient solution, at photosynthetically active radiation levels of 15, 30 and 60 W m^-2 at a daylength of 16 h, a temperature of 20°C and a relative humidity of 60% throughout. Development of the plant and growth of the leaves were measured. High irradiance accelerated development proportionally in all phases from germination, through leaf initiation, primordial flower formation and the maturation of all plant organs until anthesis. High irradiance levels stimulated the expansion of the growing shoot, which produced more and larger primordia. Under constant conditions the ratio between leaf initiation rate and mature length of a leaf remained constant, although the growth patterns [relationship between relative growth rate (RGR) and organ age] of successive leaves were not similar. Consequently, it may be assumed that, as in poplar, the increasing size of the growing shoot reflects the increase of the vascular system of sunflower. The growth patterns of the leaves depend on the developmental stage of the plant and, in the young primordial stage, also on irradiance level. In the linear phase of growth the growth pattern is independent of irradiance level.     

The influence of soil drought and partial waterlogging on water relations of Gmelina arborea seedlings

Summary Stomatal conductance of unstrossed, soil drought, and previously drought (predrought) Gmelina arborea seedlings increased in the morning and decreased before or immediately after midday. In the unstressed and predrought seedlings, leaf water potential decreased with increases in transpiration. In soil drought seedlings, there was some evidence of decreased hydraulic conductivity from soil to the plant, as indicated by the shape in the slope of the water potential/transpiration relationship. Root growth of drought plants was greater than in their unstressed counterparts at the lowest soil segment of a pot. The partial recovery of predrought seedlings was attributed to this subtantial root growth in the lowest soil segment.In the second experiment, Gmelina arborea seedlings were partially waterlogged, by flooding the polyethylene bag to half its length, for a period of 23 days. Waterlogging induced stomatal closure and reduction in leaf water potential but there was some evidence of tolerance to waterlogging towards the end of treatment. Root growth, shoot and root dry weights were slightly reduced below those of controls. After 9 days of waterlogging, adventitious roots began to form which correlated with depletion of soluble sugars in the shoot but with an increase in the roots.It is suggested that the tolerance of Gmelina plants to either soil drought or waterlogging may partly be due to partitioning of the soluble sugars from shoot to roots for production of roots and formation of adventitious roots respectively which are likely to enhance the flow of water from the soils to the plant. Therefore the plant response is very similar under conditions of increased deficits and surplus of soil water.     

不同叶位整形模式对白肋烟生长及烟叶多酚物质含量的影响

叶位整形是一项促进烟叶生长和品质提高的栽培管理措施,为明确不同叶位整形模式对白肋烟生长及多酚物质含量的影响,我们在白肋烟主产区—湖北省恩施州研究了不同叶位整形模式下不同生育期白肋烟的叶面积、叶绿素含量(CCI值)、各器官生物量和上下位叶片中多酚物质含量。结果表明:叶位整形显著影响了白肋烟生长和烟叶多酚物质含量,不但增大了不同叶位烟叶的叶面积及CCI值,还协调了各器官生物量、营养物质的合理分配以及不同叶位烟叶中多酚物质的含量;但不同叶位整形模式对白肋烟的生长影响不同,即旺长期整形(WZ)处理对白肋烟整株的促进作用较好,而团棵后期整形(TH)处理仅对上位叶效果较好。本研究采用的叶位整形栽培管理技术在保证白肋烟产量的同时,可在一定程度上促进白肋烟生长及烟叶品质的提高。     

Mechanisms for the increase in phosphorus uptake of waterlogged plants: soil phosphorus availability, root morphology and uptake kinetics

Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods. Received: 15 February 1997 / Accepted: 20 May 1997     

Siderophores of Pseudomonas putida as an iron source for dicot and monocot plants

Iron uptake from ferrated (⁵⁹Fe) pseudobactin (PSB), a Pseudomonas putida siderophore, by various plant species was studied in nutrient solution culture under short term (10 h) and long term (3 weeks) conditions. In the short term experiments, ⁵⁹Fe uptake rate from ⁵⁹FePSB by dicots (peanuts, cotton and sunflower) was relatively low when compared with ⁵⁹Fe uptake rate from ⁵⁹FeEDDHA. Iron uptake rate from ⁵⁹FePSB was pH and concentration dependent, as was the Fe uptake rate from ⁵⁹FeEDDHA. The rate was about 10 times lower than that of Fe uptake from the synthetic chelate. Results were similar for long term experiments.Monocots (sorghum) in short term experiments exhibited significantly higher uptake rate of Fe from FePSB than from FeEDDHA. In long term experiments, FePSB was less efficient than FeEDDHA as an Fe source for sorghum at pH 6, but the same levels of leaf chlorophyll concentration were obtained at pH 7.3.Fe uptake rates by dicots from the siderophore and FeEDDHA were found to correlate with Fe reduction rates and reduction potentials (E₀) of both chelates. Therefore, it is suggested that the reduction mechanism governs the Fe uptake process from PSB by dicots. Further studies will be conducted to determine the role of pH in Fe aquisition from PSB by monocots.     

间接性害虫为害与作物产量损失的关系Ⅰ.食叶害虫

本文将繁多的农作物害虫分为间接性害虫和直接性害虫.间接性害虫造成的作物的某类器官或组织的损失率小于产量损失率.食叶害虫是间接性害虫中的一大类.作物对叶面积损失的产量反应很不一致,从完全失收到增产10倍.影响叶面积损失与产量关系的首要因素通常是作物在受害时的生长阶段.在叶面积损失率一定时,处于生长中期(最终营养库迅速增大期)的作物出现最大程度减产.在损失率过大,上部功能叶受害,为害持续时间过长,作物矮秆紧凑,水、肥及气象条件不良以及损失的叶面积分布不均匀等情形下,叶片受害后易于减产;反之则减产较少甚至增产.从分散的材料中归纳出这一基本关系,对当前广泛开展的食叶害虫的产量损失评价工作可能有参考和改进意义.     

根土空间对高粱根系生理特性及产量的影响

采用尼龙袋（允许水分和养分自由通过）装土栽培作物的方法,研究了根系生长空间对高粱根系生理特性及产量的影响.结果表明,限制根系生长空间影响了高粱的生长,不同程度地降低了高粱的株高、叶面积、花后旗叶SOD及POD活性、总根长、根系吸收面积、根系与地上部干重、养分吸收量及最终产量,但增加了根系活力及活性吸收面积占总吸收面积的百分数.施肥有利于改善高粱根系在空间胁迫下的生长,增加根系吸收面积和活力,促进根系对养分的吸收,在一定程度上延缓根系生长空间不足所造成的不良影响.     

花期渍水逆境下氮素对油菜产量及氮肥利用效率的影响

温室盆栽试验条件下,设置渍水和对照2个水分处理,每个水分处理下设置3个施氮水平(0.05、0.2、0.3 g N·kg^-1土),研究了花后渍水逆境下氮素营养对两个氮高效基因型‘Monty’、‘湘油15’和两个氮低效基因型‘R210’、‘Bin270’油菜产量、产量性能及氮肥利用效率的影响.结果表明:与对照相比,花后渍水处理显著降低了油菜的单株角果数、千粒重、每角粒数和籽粒产量.在适宜水分条件下,增施氮肥显著增加了油菜籽粒产量,而在渍水逆境处理下,增施氮肥对油菜籽粒产量的形成贡献不大.氮高效基因型较氮低效基因型对花后渍水逆境下的籽粒灌浆充实具有一定的促进作用.在同一水分处理下,花后渍水明显降低了油菜氮肥利用率、氮肥偏生产力、氮肥农学利用率、氮素吸收效率和氮收获指数,渍水显著影响了不同基因型油菜的氮素吸收利用能力,而氮高效基因型在渍水逆境下较氮低效基因型更有利于将氮素转运、再分配到角果中,提高籽粒生产效率.油菜产量性能参数存在显著的水氮互作效应,水分、氮肥及水氮互作对油菜籽粒产量和产量性能参数的影响因基因型的不同而异.