Rice crop duration and leaf appearance rate in a variable thermal environment.: I. Development of an empirically based model

Variable crop duration is a major constraint to rice double cropping in arid irrigated environments, such as the Sahel. Photoperiodism and low air and water temperatures during the cool season are the major causes of variability, and cultivars are needed whose photothermal response provides a more stable crop duration. A previous study analyzed cultivar photothermal constants on the basis of progress to flowering. The present study sought to identify, on the basis of leaf appearance rates, the phenological stages that are most sensitive photothermally, and to explore technical options to screen germplasm for stable crop duration. Three Oryza sativa, indica-type rice cultivars (Jaya, IKP, IR64) were sown in the field at 15-day intervals during the dry season of 1995 (11 sowing dates) and 1996 (5 sowing dates) in Ndiaye, Senegal, under full irrigation and wide spacing to reduce microclimate variability. Mean daily water temperature (T_w) varied from 13 to 35°C. After seed soaking, the rate at which the first leaf (L₁) appeared was linearly related with T_w, with a base temperature (T_base) of about 10°C. Appearance rates of the subsequent three leaves (L₂–L₄) had a similar T_base, and presented a distinct temperature optimum (T_opt) at about 23°C, beyond which development rates decreased. Errors were too large to determine differences among cultivars in thermal constants. No significant temperature response was observed for the leaf appearances between L₅ to the flag leaf (L₁₂ to L₂₀). Crop duration to flowering varied by 45 (IR64) and 63 days (Jaya). These variations were associated with highly variable leaf numbers in all cultivars, including photoperiod-insensitive IKP. One-third of the variable duration was hypothesized to be due to a variable basic vegetative phase (BVP), caused by variable germination and leaf appearance rates, and two-thirds to variable duration of panicle induction after BVP. Water temperature was the main determinant of both sources of variability. A simulation model, describing these temperature and photoperiod effects on leaf number, growth duration and leaf appearance rates, was developed using the 1995 data, and satisfactorily validated with the 1996 data. The model was used to identify phenological-stage and cultivar-specific causes of variable crop duration.     

春季不同时期低温对小麦光合特性和粒重形成的影响

为探讨春季低温导致小麦粒重下降的生理机制,以春性品种扬麦16和半冬性品种徐麦30为材料,分别于倒二叶出生期、孕穗期和开花期对小麦进行人工气候室低温处理,研究不同时期低温对小麦光合生理特性、干物质积累和转运及强、弱势粒粒重形成的影响。结果表明,不同时期低温对叶片SPAD值的影响均表现为低温处理开始至结束后3 d持续下降,结束后6～9 d逐渐回升,两品种在低温处理结束当天和处理后3 d均以孕穗期低温处理下SPAD值降幅最大。不同时期低温处理显著降低叶片净光合速率和气孔导度,并影响花前干物质转运和花后干物质积累。与孕穗期、开花期低温处理相比,倒二叶出生期低温处理显著降低小麦花前干物质转运量,但提高花后干物质积累及其对籽粒产量的贡献率,千粒重降幅最小,扬麦16和徐麦30分别仅为4.49%和4.20%。不同时期低温处理下小麦强势粒粒重的降幅均小于弱势粒,倒二叶出生期低温处理下弱势粒粒重降幅显著低于孕穗期和开花期低温处理。相关性分析表明,低温胁迫下小麦平均千粒重和强势粒粒重相关性不显著(r=0.319,P>0.05),但与弱势粒粒重显著相关(r=0.691,P<0.05)。综上,春季低温胁迫主要通过影响小麦开花前后的光合作用和同化物向籽粒的转运,限制弱势粒的灌浆充实,最终导致粒重下降。     

Effects of sulphur dioxide and nitrogen dioxide on fourSolanum tuberosum L. cultivars

The effects of sulphur dioxide (SO₂) and nitrogen dioxide (NO₂), singly and in combination, on the shoot growth of four potato cultivars differing in maturity classification (Solanum tuberosum L. ‘Superior,’ ‘Norchip,’ ‘Kennebec, rs ‘Russet Burbank’) were determined in controlled conditions. Plants were exposed to 0.11 ppm SO₂ and/or 0.11 ppm NO₂ for 24 hours a day for 7 or 14 days. There were no significant differences in leaf growth of ‘Superior’ or ‘Norchip’ plants at 7 or 14 days. Stem dry weight was significantly reduced in ‘Superior’ only after 14 days in the mixture. ‘Kennebec’ and ‘Russet Burbank’ plants had significantly less leaf area, leaf fresh weight, and leaf water content after 14 days of exposure to the mixture, but there was no significant change in dry weight. Specific leaf weight was significantly increased in the mixture treated plants of both cultivars. The two earlier maturing cultivars, ‘Superior’ and ‘Norchip,’ were less sensitive to the SO₂ and NO₂ combination than the two later maturing cultivars, ‘Kennebec’ and ‘Russet Burbank’.     

北方冬小麦旗叶光饱和点探讨

为准确估算冬小麦旗叶光饱和点的范围,采用Li-6400-40荧光探头提供不同光合有效辐射强度,同步测量了不同品种（系）、不同时期(抽穗期、开花期和灌浆期)、不同CO₂浓度及不同施氮量下小麦旗叶的气体交换和荧光参数。结果表明,运用直角双曲线修正模型拟合的饱和光强与实际观测值较为接近。外界CO₂浓度和施氮量对小麦旗叶光饱和点具有较大影响,低CO₂浓度(300 μmol·mol^-1)和低施氮量(70 kg·hm^-2)下光饱和点均比较低;而品种（系）间和测定时期间小麦旗叶光饱和点整体差异不明显。正常条件下,小麦旗叶的光饱和点整体集中在 1 700~2 000 mol·m^-2·s^-1范围,远高于目前普遍认为的1 200 mol·m^-2·s^-1,这与小麦叶片的阳生特点及实际观测结果相一致。早期广泛采用的老版本光合助手(Photosynthesis Assistant)的拟合结果明显低于观测值(P<0.05)。综合试验结果推测,早期光饱和点的研究结果偏低可能与测量CO₂浓度、氮素营养以及所用的拟合模型等因素有关。     

Application of calcium and nitrogen for mitigating heat stress effects on potatoes

This study was designed to investigate the effect of calcium and nitrogen application during heat stress on leaf calcium concentration, transpiration rate, membrane thermostability, and biomass accumulation and partitioning. Micropropagated Russet Burbank potato (Solanum tuberosum L). plants were transplanted into 20 L pots containing 1:1 (v/v) soil: perlite and exposed to 30/20C (D/N) temperatures for four weeks (weeks 9–12 after transplanting) in a controlled-environment growth room. The maximum temperature was maintained for 6 hr during the middle of the 14 hr photoperiod. The nutrition treatments were N before stress (NBS), N during stress (NDS) and Ca and N during stress (Ca+NDS). Calcium was supplied as Ca(NO₃)₂. All treatments received the same total amount of nitrogen. Native soil Ca level without amendment (550 mg Ca/kg soil) was sufficient for potato plant growth under normal temperatures. Plants given Ca and N during heat stress had the highest leaf Ca concentration and transpiration rate during and 2 weeks after conclusion of the heat stress period. When measured after 4 weeks of heat stress, area and fresh and dry weight of the most recently mature leaf was significantly greater in NDS and Ca+NDS plants compared to NBS plants. Cellular membrane thermostability (measured as ion leakage from heat-treated leaf disks) was not affected by any treatment prior to heat stress. However, leaf tissue from Ca+NDS plants exhibited significantly higher membrane thermostability compared to NBS plants after 2 and 4 weeks of heat stress. At harvest, NDS and Ca+NDS plants had significantly higher leaf/stem (fresh weight ratio) values compared to NBS plants. Also, Ca+NDS plants had significantly greater total tuber and biomass values than NBS and NDS plants. Results of this study suggest that some detrimental effects of heat stress on plant growth and stomatal function may be alleviated by Ca and N application during heat stress. The data also suggest that mitigation of heat stress by Ca and N application during heat stress may maintain plant productivity when optimum growing temperatures are restored.     

Relationship between P and N concentrations in maize and wheat leaves

Simple plant-based diagnostic tools can be used to determine crop P status. Our objectives were to establish the relationships between P and N concentrations of the uppermost collared leaf (P_L and N_L) of spring wheat (Triticum aestivum L.) and maize (Zea mays L.) during the growing season and, in particular, to determine the critical leaf P concentrations required to diagnose P deficiencies. Various N applications were evaluated over six site-years for wheat and eight site-years for maize (2004-2006) with adequate soil P for growth. Phosphorus and N concentrations of the uppermost collared leaf were determined weekly and the relationships between leaf N and P concentrations were established using only the sampling dates from the stem elongation stage for wheat and from the V8 stage of development for maize. Leaf P concentration generally decreased with decreasing N fertilization. Relationships between P_L and N_L concentrations (mg g⁻¹ DM) using all site-years and sampling dates were described by significant linear-plateau functions in both maize (P_L = 0.82 + 0.089 N_L if N_L ≤ 32.1 and P_L = 3.7 if N_L > 32.1; R² = 0.41; P < 0.001) and wheat (P_L = 0.02 + 0.106 N_L if N_L ≤ 33.2 and P_L = 3.5 if N_L > 33.2; R² = 0.42; P < 0.001). Variation among sampling dates in the relationships were noted. By restricting the sampling dates [413-496 growing degree days (5 °C basis) in wheat (i.e., stem elongation) and 1494-1579 crop heat units in maize (i.e., silking), relationships for wheat (P_L = 0.29 + 0.073 N_L, R² = 0.66; P < 0.001) and maize (P_L = 1.04 + 0.084 N_L, R² = 0.66; P < 0.001) were improved. In maize, expressing P and N concentrations on a leaf area basis (P_LA and N_LA) at silking further improved the relationship (P_LA = 0.002 + 0.101 N_LA, R² = 0.80; P < 0.001). Predictive models of critical P concentration as a function of N concentration in the uppermost collared leaf of wheat and maize were established which could be used for diagnostic purposes.     

The influence of drought and heat stress on the expression of end-use quality parameters of common wheat

The effects of drought and heat stress on quality parameters of wheat (Triticum aestivum) cultivars were studied under field conditions in a 2-year trial (2009–2010) in northwest Mexico. Under no stress conditions, rapid small-scale parameters [protein (GP; FP) content, SDS sedimentation (SDSS), mixograph peak time (MPT), swelling index of glutenin (SIG), and lactic acid retention capacity (LARC)] showed significant relationship with gluten strength (alveograph energy, W) and bread loaf volume (LV). SIG and LARC were better than SDSS and MPT for predicting W, while SDSS was better than W and SIG for predicting bread LV. Most quality traits were primarily controlled by genotype (G), although environment (E) and G × E also had significant effects. Heat and drought stress showed contrasting effects on LARC, MPT, alveograph parameters [tenacity (P), extensibility (L), P/L ratio, W] and LV. Increase in P and decrease in L resulted in higher tenacity (larger P/L), which may explain the smaller loaf volume under drought stress. In contrast, decrease in P and increase in L, may explain the improved bread volume observed under heat stress. It is advisable to select for wheat quality under both favorable and abiotic stress conditions to identify genotypes with quality stability across environments.     

Comparison of selection indices to identify productive dry bean lines under diverse environmental conditions

This research was designed to quantify the effect of seasonal rainfall on production of dry bean (Phaseolus vulgaris L.) in the Rift Valley of East Africa, where insufficient soil moisture often limits productivity, and compare methods to identify productive lines. Twenty dry bean lines were evaluated for seed yield in a randomized complete-block design under soil moisture stress and nonstress environments during 1988, 1989 and 1992. Soil moisture stress levels were imposed by altering sowing dates (early vs. late) after the onset of the rainy season. Mean seed yield increased 8 kg ha⁻¹ for each mm of seasonal rainfall that occurred during the growing season. Lines differed in response to soil moisture stress, and their response varied with environments. Six selection indices, including arithmetic mean (AM), geometric mean (GM), drought response index (DRI), susceptibility index (S), response to drought (RD), and percent reduction (PR), were calculated for each line to determine correlations between indices and yields in stress (Y_s) and nonstress (Y_ns) environments. AM and GM were the only indices positively correlated with both Y_s and Y_ns. AM had the largest correlation with Y_ns (r=0.90) whereas GM had the largest correlation with Y_s (r=0.93). DRI, PR and S were correlated with Y_s (r=0.86, −0.82 and −0.83, respectively) but not with Y_ns. Conversely, the index RD was correlated with Y_ns (r=0.73) but not Y_s. The indices PR and S evaluated change in line performance across environments rather than line performance in either environment. GM and AM appear to be the most useful selection indices for identifying high yielding lines for both nonstress (early sown) and stress (late sown) conditions in the Rift Valley, while DRI has potential for use as a selection criteria only for stress environments.     

Effect of nitrogen supply on leaf appearance,leaf growth,leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N_a (g m⁻² N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain N_a and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0 g N pot⁻¹) and five rates (0.5–6.0 g pot⁻¹) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P_max, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N_a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P_max and N_a. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation.     

减少灌水次数对河北冬性强筋小麦产量和品质的影响

为明确不同生态环境下减少灌水次数对冬性强筋小麦产量和品质的影响,以冬性强筋小麦品种农优3号和中麦998为材料,分别在冀中北生态区的徐水区和冀东生态区的昌黎县进行大田试验,设3个灌水次数处理(CK:越冬水+拔节水+开花水;W_2:越冬水+拔节水;W_1:越冬水),研究了不同灌水次数对冬性强筋小麦叶面积系数、干物质积累、籽粒产量和品质的影响。结果表明,随灌水次数减少,两个供试小麦品种孕穗期叶面积系数呈下降趋势,W_1处理显著低于其他处理;减少灌水次数导致2个冬性强筋小麦地上部的干物质积累量显著降低,而对收获指数的影响因品种而异,其中农优3号收获指数呈上升趋势,而中麦998以W_2处理最大。减少灌水次数使冬性强筋小麦有效穗数、穗粒数和千粒重显著降低,导致产量显著降低。灌水次数减少造成冬性强筋小麦籽粒容重和蛋白质含量提高,稳定时间延长,但湿面筋含量和沉降值下降。本研究条件下,徐水点农优3号的产量较高,而昌黎点中麦998的产量较高;相同灌水处理下,同一品种在昌黎点的品质指标优于徐水试验点。综上,在河北冬性强筋小麦种植区可以选用灌越冬水和拔节水协调其籽粒产量和品质。     

Effect of nitrogen supply on leaf growth,leaf nitrogen economy and photosynthetic capacity in potato

Literature reports show little effect of nitrogen supply on radiation use efficiency in potato and in other dicotyledonous C₃ species. This paper tests the hypothesis that potato reduces leaf size rather than leaf nitrogen concentration and photosynthetic capacity when nitrogen is in short supply. Four pot experiments with different rates of nitrogen supply were conducted in glasshouses. For two leaf numbers measurements were made of leaf area, P_max (rate of photosynthesis for saturating irradiance), specific leaf weight, and concentrations of total nitrogen and nitrate, all as a function of leaf age.Area per leaf was sensitive to nitrogen supply (about a factor 3 between extreme N treatments). P_max declined with leaf age. There were no systematic effects of nitrogen supply on P_max and on its change with leaf age, except that in some cases P_max of leaves of high N treatments was lower than P_max of low N treatments during part of the life span (leaf age of ca. 20–50 days). The dominant effect of nitrogen supply was on leaf size and not on P_max or leaf N content. P_max versus areal organic nitrogen concentration (g N m⁻² leaf area) showed considerable scatter and, for a given nitrogen concentration, a slightly lower P_max for high N treatments than for low N treatments. Comparison with other species showed a comparatively low value of P_max in potato.     

减少灌水量对强筋小麦花后干物质和氮素积累、转运及产量的影响

为探究灌水量对强筋小麦花后干物质和氮素积累、转运及产量的影响,选用强筋小麦品种中麦998和中麦1062,在防雨棚池栽条件下,春季于拔节期和开花期灌水,每时期设600（W₆₀₀）、300（W₃₀₀）和0 m·hm^-2（W₀）3个灌水量处理,研究了减少灌水量对强筋小麦花后干物质含量、氮素积累和转运、籽粒产量、籽粒蛋白质含量和产量的影响。结果表明,随春季灌水量的减少,强筋小麦植株干物质积累量、氮素积累量、粒重比、叶重比、籽粒产量和蛋白质产量均表现为下降趋势,而蛋白质含量和水分利用效率呈上升趋势。两品种叶片氮素转运量和氮素转运效率以W₃₀₀处理下最高,且叶片氮素转运效率在W₃₀₀和W₆₀₀处理之间均无显著差异。中麦1062在W₀和W₃₀₀处理下水分利用效率无显著差异,中麦998在W₃₀₀和W₆₀₀处理下蛋白质含量无显著差异。综上可见,W₃₀₀处理既能有效提高强筋小麦花后干物质转运量,维持较高的产量和水分利用效率,同时又能提高氮素转运量和籽粒蛋白质含量,达到节水高产的目的。     

Artificial Neural Network Modelling of Leaf Water Potential for Potatoes Using RGB Digital Images: A Greenhouse Study

Plant water status information of potato (Solanum tuberosum L. cv. Russet Burbank) is needed at the farm level for irrigation scheduling. This research investigated the feasibility of using a 5-megapixel digital camera to determine the leaf water potential (Ψ_L) of potato plants by capturing red, green, blue (RGB) digital images in the visible region of the electromagnetic spectrum. A greenhouse experiment was conducted in containerized cv. Russet Burbank potato plants subjected to five soil nitrate-nitrogen (N) levels and four soil water content levels. An artificial neural network (ANN) model, built with RGB images, RGB image transformations, RGB vegetation indices, and principal components analysis, found that for the validation data set, the measured Ψ_L and predicted Ψ_L results were from common populations. Other results showed: (1) a linear trend between soil nitrate-N levels and leaf reflectance in the G image band, (2) that the RG image bands were more suitable than the B image band for classifying leaf pigment from leaf shadow and leaf damage, (3) soil nitrate-N interacted with leaf greenness, affecting Ψ_L prediction, and (4) some image variables were more important than others in the ANN model. Although this greenhouse research shows promise, further field-based research is required to validate the selection of input neurons used and also validate the use of ANN modelling to determine Ψ_L at the plant canopy level with cv. Russet Burbank and other cultivars. In addition, an image acquisition method needs to be developed to obtain periodic representative sample coverage over a field.     

Crop rotation and N fertilization effects on growth,yield, and disease incidence in potato

Crop rotation can be an effective mechanism for reducing disease incidence and contributing nitrogen (N) to succeeding crops. Interactions of plant pathogen suppression and soil nutrient availability may also exist, adding to the cropping system complexity. This study examined the impact of crop rotation, N fertilization, and their interaction on growth, yield, andRhizoctonia solani incidence in potato (Solanum tuberosum L. Norwis). Potato was grown continuously and in two-year rotations with annual alfalfa (Medicago sativa L. Nitro), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. Ultra), and oat (Avena sativa Astro). Fertilizer was banded at potato planting with 0, 45, 90, 135, 180, or 225 kg N ha^?1 as (NH₄)₂SO₄. Approximately 58% of continuous potato possessed stem lesions caused byR. solani, but only 12 to 22% of potato stems from other rotations possessed lesions. Tuber dry weight was affected by crop rotation in 1989, a dry year, but not in 1990. Apparent N fertilizer replacement values for hairy vetch, Nitro alfalfa, white lupin, and oat were 65, 43, 26, and 11 kg N ha^?1, respectively. All crop rotations studied appeared to enhance potato production by reducing stem infection byR. solani. Vetch and alfalfa provide additional benefits through their N contributions.     

Increases in leaf artemisinin concentration in Artemisia annua in response to the application of phosphorus and boron

Malaria resurgence particularly in the third world is considerable and exacerbated by the development of multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by WHO include the use of antimalarial compounds derived from Artemisia annua L., i.e. artemisinin-based therapies. This work aims to determine how A. annua plant dry matter can be enhanced while maximising artemisinin concentration from understanding the plant's mineral requirements for P and B. Experiments with differing of P, from 5 to 120 mg L⁻¹ and B from 0.1 to 0.9 mg L⁻¹ were undertaken. Mineral nutrients were supplied in irrigation water to potted plants and after a period of growth, dry matter production and leaf artemisinin concentration were determined. Increases in P application enhanced plant growth and total dry matter production. An optimal application rate, with respect to dry matter, was apparent around 30 mg P L⁻¹. Despite increases in P application having no influence on leaf artemisinin concentration, optimal yields of artemisinin, on a per plant basis, were again achieved at supply rate around 30-60 mg L⁻¹. Increasing B application rate had little influence on dry matter production despite increases in B leaf tissue concentration promoting the total amount of B per plant. Leaf artemisinin concentration significantly increased with B application rate up to 0.6 mg B L⁻¹. The higher artemisinin concentrations when multiplied by total leaf dry matter at the higher B application rates produced an increase in total artemisinin production per plant. There was however no further significant effect on leaf artemisinin concentration when B supply concentrations increased further (0.9 mg L⁻¹). Artemisinin production varied between the two experiments to a greater extent than plant dry matter production and the reasons for this are discussed in relation to growing environments and their possible impacts on artemisinin biosynthesis.     

Sensitivity of Pectobacterium carotovorum to hydroxytyrosol-rich extracts and their effect on the development of soft rot in potato tubers during storage

A hydroxytyrosol-rich olive mill wastewater (HROMW) (29.3% weight:dry weight) and a hydroxytyrosol-rich extract (HRE) (52.7% weight:dry weight) were prepared from the fresh olive mill wastewater (OMW) using hydrolysis and post-hydrolysis purification processes. The minimal bactericidal concentrations of HROMW and HRE against Pectobacterium carotovorum subsp. carotovorum were 72 and 40 g L⁻¹, respectively. According to the European standard method (EN 1276: 1997), HROMW and HRE showed powerful disinfectant properties and reduced the viability of P. carotovorum by more than 5 log units after a contact time of 5 min at 2% dry weight:volume. Curative and preventive controls of potato soft rot were obtained by treatment of tubers with HROMW or HRE 3 days before or 3 days after their infection with P. carotovorum, respectively. The soft rot development during potato tuber storage was significantly reduced by treatment with HRE. This extract could be used in eco-friendly strategies of post-harvest disease control and could substitute for chemical pesticides.     

Effects of sulphur dioxide and nitrogen dioxide on shoot and root growth of Kennebec and Russet Burbank potato plants

The effects of sulphur dioxide (SO₂) and nitrogen dioxide (NO₂), singly and in combination, on the shoot and root growth of two potato cultivars sensitive to these pollutant gases were determined using rooted cuttings in controlled conditions. Plants were exposed to 0.11 ppm SO₂ and/or 0.11 ppm NO₂ for 24 hours a day for 7 or 14 days. Kennebec plants had significantly lower root fresh and dry weights after 7 days in the mixture treatments and lower root fresh weight in the NO₂ treatment. Russet Burbank plants were more sensitive to SO₂ and NO₂ than Kennebec. Russet Burbank plants had significantly reduced leaf area, and leaf, stem, and root fresh and dry weights after 7 and 14 days of mixture treatment, and the leaf to root dry weight ratio was higher than in control plants. The combination treatment and SO₂ alone resulted in visible injury on leaves of both cultivars. Changes in tissue water concentration, decreased specific leaf area and decreased root growth suggested that SO₂ and NO₂ altered plant water status and interfered with partitioning of dry matter from the leaves to other plant parts.     

Influence of genotype and environment on the content of 5-n alkylresorcinols,total phenols and on the antiradical activity of whole durum wheat grains

The 5-n-alkylresorcinol (AR) contents of thirty different cultivars of durum wheat grown in two years (2009 and 2010) in two Italian locations were determined and related to the total soluble phenolic content (TPC) and antiradical activity (AA). On average, AR and TPC ranged from 161.3 to 405.8 μg/g (dry matter, DM) and from 19.0 to 192.4 μg/g (DM), respectively. AA (EC₅₀ values) ranged from 70.9 to 289.2 mg of dry whole milled wheat grain (DM). The results showed that the environment (E) and the genotype (G), as well as their interactions (G × E), significantly influenced the phytochemical profiles of the samples. The contribution of G × E to the total variance was much lower than that due to the separate effects (G and E). Principal component analysis identified genotypes that were richer in ARs and more stable across environments. There were significant negative correlations between ARs and TPC (p < 0.05) and between TPC and AA (p < 0.01), but not between ARs and AA. Graphical representation was efficient in summarizing the overall antiradical profiles of the durum wheat grain in each environment.     

秋季耕作方式对旱地麦-玉二熟区小麦产量形成的影响

为明确秋季耕作方式对旱地麦-玉二熟体系小麦籽粒产量形成的影响,于2019年6月至2021年6月,在豫西典型旱作麦-玉二熟区的洛阳市孟津区小浪底镇明达村,选择前茬夏玉米免耕的田块,设置秋深松、秋免耕和秋旋耕3种耕作方式,分析了不同秋季耕作方式下两个试验年度的小麦籽粒产量及其构成因素和穗部性状以及2020-2021年度的小麦群体茎蘖数、孕穗后的旗叶净光合速率（P_n）和干物质积累转运特性。结果表明,秋季耕作方式对小麦产量、穗部性状、旗叶P_n和干物质积累转运特性均有显著的调节作用。与秋旋耕相比,秋深松的小麦茎蘖数除返青期外均显著增加,穗数增加5.74%~16.06%;秋深松虽然对小麦旗叶P_n无显著影响,但提高灌浆中后期的旗叶SPAD值,显著改善了干物质积累转运特性,从而使千粒重增加,其中2019-2020年度使穗长和小穗数分别提高7.50%和9.42%,最终使籽粒产量提高9.77%~19.09%。秋免耕后,小麦孕穗和抽穗期的叶片P_n、返青至开花期的干物质积累量、花前干物质转运量及其对籽粒产量的贡献率也较秋旋耕均显著降低,而花后干物质对籽粒产量贡献率提高7.35个百分点,从而保证了籽粒产量无显著下降。与秋免耕相比,秋深松下不同生育时期的茎蘖数均显著增加,孕穗至灌浆中后期的叶片P_n,灌浆中后期的旗叶SPAD值,返青-成熟期的干物质积累量,花前干物质转运量、转运效率及其对籽粒产量的贡献率分别提高7.16%~18.41%、10.27%、12.25%~19.97%、42.19%、4.02个百分点和11.95个百分点,其中2019-2020年度穗长和小穗数分别增加7.50%和8.41%,穗数和籽粒产量分别提高16.74%~17.63%和10.31%~23.63%。综上,秋深松不仅可增加小麦穗数,而且可改善旗叶光合及干物质积累转运特性,进而提高籽粒产量,是旱地麦-玉二熟区实现小麦高产的耕作方式。     

Simulating Organ Growth in Wheat Based on the Organ–Weight Fraction Concept

Abstract

Quantifying dry matter partitioning into individual organs of plants is a key component for simulating crop growth and yield formation. This study was undertaken to develop a dynamic module of biomass partitioning over the entire duration of growth in wheat. The partitioning fraction of shoot or root was defined as the fraction of its dry weight in plant biomass, and partitioning fraction of green leaf, stem or ear as the fraction of its dry weight in shoot mass of wheat. The functional relationships of the partitioning fraction with physiological development time for the entire growth period were established, in which harvest index (HI) regulated partitioning fraction of ear to shoot biomass as a genetic parameter. The dry weight of individual organ was the product of the respective partitioning fraction and plant weight or shoot weight. Test of the model with the field experiment data sets involving different sowing dates, plant densities and nitrogen fertilization strategies indicated a good agreement between the predicted and observed values.