Developmental Stages Of Rice Plants Research Articles

Effects of alternate wetting and drying on oxyanion-forming and cationic trace elements in rice paddy soils: impacts on arsenic, cadmium, and micronutrients in rice.

Rice is a global dietary staple and its traditional cultivation under flooded soil conditions leads to accumulation of arsenic (As) in rice grains. Alternate wetting and drying (AWD) is a widely advocated water management practice to achieve lower As concentrations in rice, water savings, and decreased methane emissions. It is not yet clear whether AWD leads to tradeoffs between concentrations of As and micronutrient elements (e.g., zinc, manganese, molybdenum) in rice grain. We analyzed pore water chemistry and rice grain composition data from a field experiment conducted in Arkansas, USA, in 2017 and 2018 to test the hypothesis that AWD will have diverging effects on oxyanion-forming (arsenic, molybdenum) vs. cationic (cadmium, zinc, manganese, copper) trace elements. This was hypothesized to occur via decreases in soil pH and/or precipitation of iron oxide minerals during oxidizing conditions under AWD. Solubility of all trace elements, except zinc, increased in more reducing conditions. Consistent with our hypothesis, AWD tended to increase grain concentrations of cationic elements while decreasing grain concentrations of oxyanionic elements. Decreases in total As in rice grains under AWD were mainly driven by changes in dimethylarsinic concentrations, with negligible changes in inorganic As. Linear mixed-effects modeling showed that effects of AWD on grain composition were more significant in 2017 compared to 2018. These differences may be related to the timing of dry-downs in the developmental stage of rice plants, with dry-downs during the heading stage of rice development leading to larger impacts on grain composition of certain elements. We also observed significant interannual variability in grain elemental composition from continuously-flooded fields and postulate the warmer temperatures in 2018 may have played a role in these differences.

Efficacy of reduced rates of chlorantraniliprole seed treatment on insect pests of irrigated drill-seeded rice.

For the past decade, insecticidal seed treatment has been the most widely used control tactic against insect pests of rice (Oryza sativa L.) in the USA. Seed treatments are used primarily to control the most economically important early-season pest of rice, the rice water weevil (Lissorhoptrus oryzophilus Kuschel). This study was conducted to evaluate the efficacy of reduced rates of chlorantraniliprole seed treatment against the rice water weevil, fall armyworm (Spodoptera frugiperda J.E. Smith), and sugarcane borer (Diatraea saccharalis F.) under field and laboratory conditions. Concentrations of chlorantraniliprole in plant tissues were determined at vegetative and reproductive developmental stages of rice plants. Chlorantraniliprole seed treatment reduced the densities of rice water weevil larvae relative to non-treated controls even at rates 75% lower than the label rate. Increased mortality of fall armyworm larvae was observed at reduced seed treatment rates relative to a non-treated control. Chlorantraniliprole seed treatment increased the mortality of sugarcane borer larvae at all rates relative to controls and the mortality was consistently higher in larvae that were fed stems from treated plants at the vegetative developmental stage than larvae that were fed stems from plants at the reproductive stage. Concentrations of chlorantraniliprole in plant tissues increased with seed treatment rate and decreased with plant age. This study has shown that reduced chlorantraniliprole seed treatment rates can provide adequate control against the rice water weevil, fall armyworm, and sugarcane borer, particularly at early developmental stages of rice plants. © 2019 Society of Chemical Industry.

BGRcast: A Disease Forecast Model to Support Decision-making for Chemical Sprays to Control Bacterial Grain Rot of Rice.

A disease forecast model for bacterial grain rot (BGR) of rice, which is caused by Burkholderia glumae, was developed in this study. The model, which was named ‘BGRcast’, determined daily conduciveness of weather conditions to epidemic development of BGR and forecasted risk of BGR development. All data that were used to develop and validate the BGRcast model were collected from field observations on disease incidence at Naju, Korea during 1998–2004 and 2010. In this study, we have proposed the environmental conduciveness as a measure of conduciveness of weather conditions for population growth of B. glumae and panicle infection in the field. The BGRcast calculated daily environmental conduciveness, Ci, based on daily minimum temperature and daily average relative humidity. With regard to the developmental stages of rice plants, the epidemic development of BGR was divided into three phases, i.e., lag, inoculum build-up and infection phases. Daily average of Ci was calculated for the inoculum build-up phase (Cinf) and the infection phase (Cinc). The Cinc and Cinf were considered environmental conduciveness for the periods of inoculum build-up in association with rice plants and panicle infection during the heading stage, respectively. The BGRcast model was able to forecast actual occurrence of BGR at the probability of 71.4% and its false alarm ratio was 47.6%. With the thresholds of Cinc = 0.3 and Cinf = 0.5, the model was able to provide advisories that could be used to make decisions on whether to spray bactericide at the pre- and post-heading stage.

Cold Tolerance in Rice Plants: Why, How and When?

Low temperature stress is one of the major abiotic factors which reduce rice yield in several countries [1]. Losses can range from 0.5 to 2.5 t/ha [2] and grain yields can drop by up to 26% [3], mostly due to low temperature during the reproductive stage, even though cold temperature can be harmful during the entire developmental stage of rice plants, from germination to grain filling [4,5]. During germination, the most common symptoms of cold temperature damage are delayed and lower percentage of germination [6]. During early growth stages, it can severely affect seedling establishment, showing yellowing of the leaves, growth retardation, and decreased tillering [5]. When cold coincides with the reproductive stage of the rice plant, sterility of the spikelets is the most common symptom of injury, but incomplete panicle exsertion and spikelet abortion may also occur, along with delayed and incomplete grain maturation [7]. Irrespective of the developmental stage, the duration of low temperature is an essential element determining the extent of cold damage; however, the critical air temperature that induces cold damage depends on the cultivar [8]. It is already known that some rice cultivars can tolerate stressful conditions and are able to grow under low temperature [9]. These cold tolerant rice cultivars normally belong to japonica subspecies [10], which are more adapted to temperate climates. Therefore, the challenge still remains to develop cold tolerant indica genotypes suitable for high-latitude regions.

Seasonal trends and environmental controls of methane emissions in a rice paddy field in Northern Italy

Abstract. Rice paddy fields are one of the greatest anthropogenic sources of methane (CH4), the third most important greenhouse gas after water vapour and carbon dioxide. In agricultural fields, CH4 is usually measured with the closed chamber technique, resulting in discontinuous series of measurements performed over a limited area, that generally do not provide sufficient information on the short-term variation of the fluxes. On the contrary, aerodynamic techniques have been rarely applied for the measurement of CH4 fluxes in rice paddy fields. The eddy covariance (EC) technique provides integrated continuous measurements over a large area and may increase our understanding of the underlying processes and diurnal and seasonal pattern of CH4 emissions in this ecosystem. For this purpose a Fast Methane Analyzer (Los Gatos Research Ltd.) was installed in a rice paddy field in the Po Valley (Northern Italy). Methane fluxes were measured during the rice growing season with both EC and manually operated closed chambers. Methane fluxes were strongly influenced by the height of the water table, with emissions peaking when it was above 10–12 cm. Soil temperature and the developmental stage of rice plants were also responsible of the seasonal variation on the fluxes. The measured EC fluxes showed a diurnal cycle in the emissions, which was more relevant during the vegetative period, and with CH4 emissions being higher in the late evening, possibly associated with higher water temperature. The comparison between the two measurement techniques shows that greater fluxes are measured with the chambers, especially when higher fluxes are being produced, resulting in 30 % higher seasonal estimations with the chambers than with the EC (41.1 and 31.7 g CH4 m−2 measured with chambers and EC respectively) and even greater differences are found if shorter periods with high chamber sampling frequency are compared. The differences may be a result of the combined effect of overestimation with the chambers and of the possible underestimation by the EC technique.

Isolation of Allelopathic Substances in Rice Seedlings

SummaryIn order to evaluate the allelopathic potential of the early developmental stage of rice plants (Oryza sativa L.), a search for allelopathic substances was undertaken in acetone extract of 10-d-old rice seedlings. Two growth-inhibiting substances were found in the neutral fraction of the extract after silica gel column chromatography, and one substance was further purified by thin layer chromatography, C18 Sep Pack cartridge and HPLC. The purified substance inhibited the growth of lettuce (Lactuca sativa L.) at concentrations greater than 0.3 μgmL–1. These two substances may be released into the environment, either as exudates from living tissues or leachates from residues of the plant, and act as allelochemicals to other plants, which should be investigated further in the laboratory and the field.

A Simple Model to Predict the Developmental Stages of Rice Panicles Using the Effective Accumulative Temperature.

水稲冷害早期警戒システムにおいて東北全域の水稲の生育監視に適用する幼穂および玄米の主な発育ステージを予測するモデルを作成した.これらのモデルは日平均気温10℃以上の有効積算気温を用いて気象被害予測,栽培管理の支援に必要な発育ステージを推定するものである.幼穂の発育モデルは,幼穂形成期を起点として花粉母細胞分化期,減数分裂期,花粉内容充実期,出穂期を推定するものであり,日平均気温18～26℃の温度勾配温室でポット栽培した主稈を対象とした有効積算気温に,圃場の群落を構成する株内の主稈と他の茎の出穂変異を加味して作成した.玄米の発育モデルは出穂期から乳熟期,糊熟期,黄熱期,成熟期を推定するものであり,1998年と1999年の盛岡における東北の基幹12品種の各発育ステージの到達日から有効積算気温を決定した.本モデルを用いて2000年の盛岡で栽培した12品種の出穂期および成熟期の予測精度を検証したところ,推定誤差はそれぞれ1.2日,2.1日であった.また,宮城県,山形県の農家圃場における出穂期と成熟過程の予測精度は比較的高かった.さらに既報の主稈葉齢進度モデルに幼穂と玄米の発育モデルを組み合わせて幼穂形成期,出穂期で切り替えて利用することにより,活着後から成熟期までの発育ステージを予測することも可能であった.

A Model to Estimate the Increase of Leaf Number on the Main Culm of the Rice Plant.

水稲冷害の早期警戒システムにおいて東北全域の生育監視に適用する止葉展開期までの発育ステージを葉齢で予測するモデルを作成した.本モデルでは, 主稈葉齢が1進むのに必要な10～24℃の有効積算気温を出葉間隔とした.葉齢増加による出葉間隔の転換点を主稈葉齢9.1と11.1とし, 3時期に分割した.出葉間隔はPhase Iは一定, Phase IIでは一定の割合で拡大し, Phase IIIで再び一定とする.葉齢は出葉間隔に基づいて, 日々の葉齢進度を積算して推定する.東北の基幹12品種のうち, 1997年と1998年の7品種の盛岡における出葉経過からモデルのパラメータを決定した.本モデルによる推定葉齢と実測葉齢を1999年の盛岡について比較すると, 「おきにいり」を除いた11品種で誤差平均が0.25葉, 日数に換算すると1.7日であった.作成したモデルを宮城県松山町と山形県最上町の農家圃場で検証したところ, 予測精度は比較的高かった.ただし, 出葉間隔は分げつの影響も受けるため, 初期に分げつ形成が旺盛な生育型では予測精度が低くなった.

RFLP facilitated analysis of tiller and leaf angles in rice ( Oryza sativa L.)

Plant type is an important composite trait associated with the yield potential in rice and other cereal crops. Several characters associated with the plant type of modern rice cultivars including tiller angle, leaf and flag leaf angle, were investigated using a complete linkage map with 115 well distributed RFLP markers and progeny testing of 2418 F2 derived F4 lines from a cross between O. sativa ssp. japonica cv. ‘Lemont’ and spp. indica cv. ‘Teqing’. One major gene (Ta) and 11 QTLs were largely responsible for the tremendous variation of the three plant type characters in the Lemont/Teqing F2 population. The major gene, Ta, located between RZ228 and RG667 on chromosome 9, accounted for 47.5% of the phenotypic variation in tiller angle and had large pleiotropic effects on both leaf and flag leaf angles. This gene plus four QTLs accounted for 69.1% of the genotypic variation in tiller angle. Eight additional QTLs for leaf and flag leaf angles were also identified, which collectively explained 52.0 and 66.4% of the genotypic variation of these traits. Ta and three QTLs ( QFla2, QFla5 and QFla7) apparently affected the related plant type characters differently, suggesting their possible differential expression in different developmental stages of rice plants or possibly clustering of different genes affecting these traits. Plant type, and consequently grain yield of rice, may be improved by deliberately manipulating these QTLs in a marker-assisted selection program.

Stomatal Resistance of Rice Leaves as Influenced by Radiation Intensity and Air Humidity

This paper describes results of field experiments of relationships between meteorological conditions and stomatal resistance of rice leaves. The magnitude of stomatal resistance of rice leaves was measured by a porometer at important three developmental stages of rice plants. Stomatal resistance (rs) changed very clearly throughout sunny days in relation to diurnal variation in solar radiation intensity (St) and leaf air vapor concentration deficit (HD).Stomatal resistance of the adaxial surface of rice leaves was found to be the same to that of the abaxial surface in the magnitude, indicating that the water vapor fluxes at the both surfaces of rice leaves are equal with each other. The dependence of non-dimensional stomatal resistance [rs/rm·k(HD)2] on solar radiation intensity (St) was well approximated by a hyperbolic function. The relationship between HD and [rs/rm(1+St, m/St)] was expressed by a quadratic function of HD.

On the Diurnal Variation of Leaf Water Content on an Areal Basis in the Rice Plant

In a previous report4) it was made clear that the stomata of leaf blade of rice plants closed to a considerable extent on fine days even when they grew in submerged paddy field. For this time an investigation was undertaken to clarify the diurnal variation of leaf water content on an areal basis in some developmental stages of rice plants under various weather conditions. Maximal water content was obtained for 12th and 13th leaf, fully expanded just at the panicle formation stage. The water content decreased more and more for both upper and lower leaves as away from the relevant leaves. The water content of each successive leaf followed the diurnal variation pattern of taking the maximal value in eariy morning and decreasing towards noon. But the range of variation was wider at the tillering stage, becoming narrower after the booting stage. As for the effect of weather condition, the midday decrease of water content was rather remarkable on fine days accompanied with intense transpiration, but the difference of diurnal variation between fine and cloudy days was small as was expected. From this result it was suggested that the water content of rice plants grown in submerged condition did not debrease below a certain limit, owing perhaps to the increase of water absorption in accordance with intensive transpiration or stomatal closure due to the decrease of water content. In the afternoon of fine days, stomatal aperture became much smaller than on cloudy days. So it was considered that the slight variation of water content gave much influence upon stomatal aperture when water content of leaf blade decreased to a certain limit and that this influcnce became more prominent after the booting stage with narrower range of the variation of water content. Lastly the areal weight or the dry weight per leaf area was much larger in fine days compared with cloudy days, suggesting the effect of dry weight increase upon the decrease of customary leaf water content on a dry weight or fresh weight basis.

Analysis of Yield-Determining Process and Its Application to Yield-Prediction and Culture Improvement of Lowland Rice : CVI. On the relation between leaf number index and number of days before heading

The number of days before heading has hitherto been used to express developmental stages of rice plants, and it is known that the number of days before heading can also been used practically in case of a definite variety grown in a definite area. However, in fact, the number of days before heading is strongly affected by many factors such as varieties, time of seeding or transplanting, cultural conditions and so on. On the other hand, the number of leaves on the main culm is also affected by the factors mentioned above. Therefore, the authors have tried to clarify the relation between the leaf number index, which is possible to express the developmental stages of young panicles of rice plants, and the number of days before heading at various stages, and the following results have beed obtained. 1. The relation between the leaf number index (LNI) and the number of days before heading (DBH) is variable with varieties, time of seeding or transplanting and cultural conditions etc. For instance, the number of days before heading corresponding to a given developmental stage (a given LNI) is larger in late varieties than in early ones, in the case of an identical seeding time. Likewise, DBH is larger in early seeding time than in late one, in case of an identical variety being used. These facts suggests that the variation in the number of days before heading corresponding to a given leaf number index might be mainly governed by the number of days from seeding to heading (DSH). 2. The number of days before heading is divided by the number of days from seeding to heading and is multiplied by 100, and then its relation to the leaf number index has been examined, so that the time difference in the number of days before heading caused by various factors may be eliminated. As a result of it, relation between leaf number index and DBH/DSH ratio shows always a definite tendency irrespective of variation caused by varieties and other factors. Accordingly, the values of DBH/DSH have been proved to be effectively used for estimating each developmental stage of young panicles in rice.

Effect of Different Meteorological Conditions on the First and Late Developmetal Stage of Rice Plant at Unsafty Region Against Cool Weather

In 1959, 1960 and 1961, the experiments were carried out to make clear the characteristic growth of rice plants in high lands Surige (Hiraga town level 350m) and in seaside Shimooguni (Kanita town) where the north-easterlies named “Yamase wind” prevailed, comparing with inland districts (Kuroishi) in Aomori prefecture.In order to investigate the effect of meteorological conditions on the late developmental stage of rice plants, paddy planted in pots were removed between inner districts and high lands or seaside region mutually on determined date (the heading date and the differentating stage of branch primorda).

Ecological Studies on the Establishment of Regionality in Early Planting Culture and Great Harvest of Rice Plant

In 1959 and 1960, the experiments were carried out to make clear the characteristic growth of rice plants in high lands Surige (Hiraga town level 350m) and Utarube (Towada town level 400m), and in seaside Shimooguni (Kanita town) and Itikawa (Hatinohe city) where the north-easterlies named “Yamase wind” prevailed, comparing with inland districts (Kuroishi and Fujisaka) in Aomori Prefecture. In order to investigate the effect of meteorological conditions on the late developmental stage of rice plants, the plants planted in pots were removed between inner districts and high lands or seaside region mutually on determined dates.Results obtained are as follows:(1) In the high lands and seaside region, the growth of early developmental stage of rice plants was inferior to inner districts and the heading was dates were retarded.(2) The safety time for the heading was longer in inner districts than in high lands and in seaside region (See Fig. 2)(3) Main characteristics in growth of rice plants varied by exchanging the places, naimely the meteorological conditions in late stage of the growth.

Effect of Different Meteorological Conditions on the Late Development Stage of Rice Plant (2)

In order to investigate the effect of meteorological conditions on the late developmental stage of rice plants, the exchanging method of plants in pots between two stations was adopted, where the diurnal temperature change is respectively large and small, Obtained resuets are as follow. The rice plant, placed where is large in diurnal temperature change, showes a good growth and a strong registance to Brown spot.