Zhen-Lin Wang

Comparison of Starch Granule Size Distribution Between Hard and Soft Wheat Cultivars in Eastern China

Abstract Granule size distribution of wheat starch is an important characteristic that can affect its chemical composition and functionality. Two types of wheat cultivars, the hard and soft wheat cultivars, grown at Taian Experimental Station of Shandong Agricultural University, Taian, Shandong, China, were examined in this study. The granule size distribution and amylose contents in wheat grains were studied and compared, and relationships between the properties were identified. A clear bimodal distribution of granule size was shown in all wheat cultivars. Volume distribution of starch granules shows the typical bimodal with peak values in the ranges of 5.6-6.1 μm and 20.7-24.9 μm, respectively. Also, granule surface area distribution was bimodal with peak values in the ranges of 2.4-3.2 μm and 20.7-24.9 μm, respectively. Number distribution of granules was a typical population with a peak value in the range of 0.54-1.05 μm. Contributions from the granules

Starch Granule Size Distribution from Seven Wheat Cultivars Under Different Water Regimes

ABSTRACT Seven wheat cultivars with different starch contents were used as materials to investigate the distribution of grain starch granule size under irrigated and rainfed conditions. In mature grains, the diameter of starch granules was 0.37–52.6 μm, and the percent volume distribution showed a two-peak curve with the mean particle diameter of 5 (B-type) and 25 μm (A-type) at each peak. The volume percentages of A- and B-types were 52.7–65.5% and 34.5–47.3%, respectively. A two-peak curve is also shown in percent surface area distribution of starch granules, but only one peak in percent number. Both irrigated and rainfed conditions had a significant effect on the starch granule size distribution of the seven cultivars. As compared with irrigated treatment, rainfed treatment affected the distribution of starch granules in grains of all cultivars through increasing the volume percentage and surface area percentage of 2–9.8 and 9.8 and >18.8 μm starch granu...

Distribution of Starch Granule Size in Grains of Wheat Grown Under Irrigated and Rainfed Conditions

Abstract Starch granule comprises A and B types in mature wheat ( Triticum aestivum L.) grains, which are different in chemical composition and functional properties. The granule size distribution of wheat starch is affected by both genotypic and environmental factors. Two wheat cultivars, Lumai 21 (starch content 68.9%) and De 99-3 (starch content 64.6%) were used to investigate the distribution of grain starch granule size, under irrigated and rainfed conditions, at Taian and Dezhou in Shandong Province, in the 2004–2005 growing season. In mature grains, the diameter of starch granules ranged from 0.37 to 52.60 μm, and the percent volume distribution showed a two-peak curve with the mean granule diameter of 5 (B type) and 25 μm (A type) at each peak. The volume percentages of A and B types were 56.1–65.5% and 34.5–43.9%, respectively. The two-peak curve was also shown in the percent surface area distribution of starch granules, but only 1 peak was seen in the percent number, because the number of B-type granules accounted for over 99% of the total starch granules. Compared with the irrigated treatment, the rainfed treatment affected the distribution of starch granules in grains of both cultivars by increasing the percent volume and the percent surface area of 2.0–9.8 and 18.8 μm starch granules. Soil water deficit also decreased the contents of amylose and starch in grains, but increased protein content, peak viscosity, and final viscosity. This indicated that the rainfed treatment probably improved the wheat grain quality. In the 2 cultivars, the contents of amylose and starch in grains had significantly negative correlations to the percent volume of 2.0–9.8 and 9.8 μm) are high in both the contents of amylose and starch.

Photosynthetic Characteristics and Antioxidative Metabolism of Flag Leaves in Responses to Nitrogen Application During Grain Filling of Field-Grown Wheat

Abstract A two-factorial experiment was conducted with two wheat cultivars, SN1391 (large spike and large grain) and GC8901 (multiple spike and medium grain), and two nitrogen (N) application rates (12 and 24 g N m −2 ), to investigate the responses of photosynthetic characteristics and antioxidative metabolism to nitrogen rates in flag leaves of field-grown wheat during grain filling. The results showed that the content of N and chlorophyll (Chl) in wheat flag leaves decreased after anthesis and the net photosynthetic rate (Pn), effective quantum yield of PS II (Φ PS II ), efficiency of excitation capture by open PS II reaction centers (Fv′/Fm′), and photochemical quenching coefficient (q p ) began to decrease at 14 days after anthesis. However, the maximal efficiency of PS II photochemistry (Fv/Fm) decreased slightly until the late period of senescence and the nonphotochemical quenching coefficient (NPQ) increased during flag leaves senescence. As a result, a conflict came into being between absorption and utilization to light energy in flag leaves during senescence, which might accelerate the senescence of flag leaves. Compared with GC8901, the lower plant population of SN1391 during grain filling was helpful to maintain the higher content of photosynthetic pigment, activity of PS II, and Pn in flag leaves during senescence. The delayed decrease in antioxidative enzyme activity and the lower degree of membrane lipid peroxidation in the senescing leaves of SN1391 were beneficial to protect the photosynthetic apparatus, which lead to the prolonged duration of CO 2 assimilation. With the increase of N application, the Chl content of SN1391 flag leaves and the efficiency of excitation captured by open PS II centers increased. At the same time, the thermal dissipation in SN1391 flag leaves at high N (HN) treatment decreased and Φ PS II improved greatly, which were favorable to the increase of Pn. The SOD, POD, CAT and APX activities in the flag leaves of SN1391 increased markedly at HN treatment, indicating that these enzymes could clean more active oxygen and decrease the degree of membrane lipid peroxidation. In this way, the ability of SN1391 to protect photosynthetic apparatus was improved with the increase of N. In the HN treatment, the decreased activity of PS II and increased thermal dissipation resulted in the decline of Pn in flag leaves of GC8901. Meanwhile, the decreased antioxidative enzyme activities and the increased degree of membrane lipid peroxidation had indirect and unfavorable influences on CO 2 assimilation. This implied that the conflict between absorption and utilization to energy in senescing leaves was an important reason which induced and accelerated the senescence of wheat leaves in the field. The photosynthetic characteristics and antioxidative metabolism of flag leaves during grain filling were markedly different among wheat cultivars. The effects of nitrogen rate on the photosynthetic and senescent characteristics of flag leaves also varied with wheat cultivars.

Endogenous Hormone Concentration in Developing Tuberous Roots of Different Sweet Potato Genotypes

A field trial was conducted to investigate the changes of endogenous hormone concentration (EHC) during formation and thickening of tuberous roots in sweet potato (Ipomoea batatas L.) of different genotypes: Xushu 18, Minamiyutaka, and I. trifida-K123. The results of this study suggested that the concentrations of zeatin riboside (ZR), dihydro-zeatin riboside (DHZR), abscisic acid (ABA), indole-3-acetic acid (IAA), and isopentenyl-adenine (IPA) of Xushu 18 and Minamiyutaka were significantly higher than those of I. trifida-K123. Dry tuberous root yields were positively correlated with the concentration of ABA, ZR, and DHZR at 1 or 5% significant level, but were not obviously correlated with the concentrations of IAA, IPA, and GA4. The concentrations of ABA, ZR and DHZR played very important roles in the tuberous root formation and thickening in sweet potato. The concentrations of ZR, DHZR, ABA, and IAA in the upper or inner portion of tuberous roots were significantly higher than those toward the end of the root or its outer portion. Meanwhile, EHC of large-sized tuberous roots were significantly higher than those of medium- or small-sized tubers during the early thickening period. In the rapid thickening period of tuberous roots, EHC of medium-sized tubers were the highest. However, at the late-thickening period, EHC of small-sized tubers ranked the highest.

Physiological and Molecular Response of Wheat Roots to Nitrate Supply in Seedling Stage

The objective of this study was to understand the morphological, physiological, and molecular responses of wheat roots to nitrate supply at seedling stage. Two wheat genotypes, Jimai 22 and Shannong 15, were grown in Hoaglands nutrient solution with different nitrate levels at seedling stage. Results indicated that the plant dry weight and N accumulation increased with the increase of nitrate supply. The number of axial root, total uptake area (TUA), and active uptake area (AUA) increased with more nitrate supply. Correlation analysis indicated that significant positive correlations existed between N accumulation and dry weight, N accumulation and AUA, and N accumulation and AUA/TUA. Although, the expressions of NRT2.1, NRT2.2, and NRT2.3 decreased with nitrate supply increased, the expressions of NRT1, NRT2.1, and NRT2.3 could maintain high level at N3 treatment. The free amino acid and NO3− content in shoot also increased with the increased nitrate application, but no significant difference was found in root among the treatments. These results implied that the increase of N uptake by nitrate supply was due to the morphological and physiological responses of wheat roots and the high expression level of TaNRT genes. Similarly, the contribution of morphological, physiological, and molecular parameters was different between two genotypes of wheat.

Ultrasonic Acoustic Emissions from Leaf Xylem of Potted Wheat Subject to a Soil Drought and Rewatering Cycle

Ultrasonic acoustic emissions (AEs) from leaf xylem of both water stressed and well watered potted winter wheat (Triticum aestivum L.) plants during drought and rewatering cycle were investigated with a PCI-2 Based AE System (Physical Acoustics Corp. New Jersey, USA) for estimation of leaf xylem cavitation and embolism. Very few AEs occurred in xylem of wheat leaves in well-watered plant, and also in plant subject to mild and moderate soil water stress conditions over the first 4 d of the drought cycle. Great amounts of AEs have occurred since d 5 of the drought cycle as plant showed obvious leaf curling, indicating significant cavitation in leaf xylem on plant exposed to severe soil water deficit. At this point, relative soil water content (RSWC) and leaf xylem pressure (ψ1) dropped to 24.0-26.5% and-1.92MPa, respectively, with reductions in leaf stomatal conductance (g(subscript s)), leaf transpiration (Tr) and leaf CO2 assimilation rate (A) of as much as 69.8, 60.7 and 46.5%, respectively. The effect of soil water deficit was in the order g(subscript s)＞Tr＞A＞AE. Waveform physical property parameters such as amplitude, counts, rise time, duration, absolute energy and signal strength were analyzed. These parameters varied within very broad ranges, with frequency distribution of most parameters being well fitted by the exponential function y=y(subscript o)-A exp (-x/t). The proportion of stronger AE signals rose as soil dehydrated. While AEs occurrence in water stressed plant remained higher than in well-watered control at the following day after rewatering, waveform signal strength and related physical property parameters dropped immediately to that of control. Difference in AEs occurrence characterization between field-grown and potted wheat leaves was discussed.

Nitric Oxide Content in Wheat Leaves and Its Relation to Programmed Cell Death of Main Stem and Tillers Under Different Nitrogen Levels

Abstract Nitric oxide (NO) is a key signaling molecule in different physiological processes of plants, including programmed cell death (PCD). PCD of tillers plays an important role in surviving which are major components of grain yield. PCD was triggered in wheat leaves of main stem and tillers by NO content under different nitrogen treatments. In wheat, NO could be synthesized endogenously by nitrate reductase (NR). As an inducible enzyme, NR activity was closely related to substrate concentration. Therefore, different nitrogen levels would change NR activity and NO production. The objective of this study was to determine the effects of NR activity, NO production, and the correlation between them on different tillers growth, development, senescence, and kernel protein content under different nitrogen levels. Field-experiments were conducted in 2009–2011 growing seasons, using two wheat cultivars with different spike-types. Results showed that for main stem and primary tillers, NR activity and NO content reached high level at heading stage, while for secondary tiller, the level of NR activity was low, but NO content was high in the present research. The NO synthesis depending on NR activity in wheat leaves was significant in the early growing stage, but the NO synthesis weakened with the progress of growing period. NO was related to the senescence of wheat leaves, but PCD was more sensitive to marked changes of NO content than NO content itself. N application had marked influence on the aging process of primary tiller, while had little influence on that of main stem and secondary tiller. Moreover, N fertilizer application could increase spike rate and protein content of primary tiller by N fertilizer application.

Effects of Exogenous ABA and 6-BA on Flag Leaf Senescence in Different Types of Stay-Green Wheat and Relevant Physiological Mechanisms

The effects of exogenous abscisic acid (ABA) and 6-benzyladenine (6-BA) on the contents of chlorophyll, malondialdehyde (MDA), and endogenous hormones and activities of antioxidant enzymes in flag leaf were investigated using stay-green wheat cultivar Wennong 6 and a control cultivar Jimai 20. The results showed that ABA and 6-BA obviously increased chlorophyll content from 7 days after anthesis (DAA) to 28 DAA. Likewise, the soluble protein contents in ABA-treated and 6-BA-treated plants significantly increased from 21 DAA to 35 DAA, while the MDA content decreased from 28 DAA to 35 DAA. Although ABA applications decreased endogenous zeatin (ZR) and ABA contents from 28 DAA to 35 DAA, the endogenous auxin (IAA) and gibberellin (GA) contents increased. In both cultivars, 6-BA significantly increased the ZR content, but decreased the ABA content in Jimai 20 from 21 DAA to 35 DAA. Exogenous ABA and 6-BA significantly enhanced superoxide dismutase (SOD) activity, while had no significant effects on peroxidase (POD) and catalase (CAT) activities in Wennong 6 and increased POD activity in Jimai 20 from 7 DAA to 28 DAA. Exogenous 6-BA significantly increased POD and CAT activities in both cultivars. Meanwhile, treatments with ABA and 6-BA significantly increased 1000-grain weight and yield, that had no effects on grain number per spike and spike number per square meter.

Mechanisms of Tiller Occurrence Affected by Exogenous IAA,GA_3 ,and ABA in Wheat with Different Spike-types

Two winter wheat cultivars,Shannong 15 and Shannong 8355,were used to study the effects of exogenous indole-3-acetic acid(IAA),gibberellic acid 3(GA3),and abscisic acid(ABA)on tiller occurrence in wheat and the underlying mechanism.Exogenous IAA and GA3 inhibited occurrence of wheat tiller,while exogenous ABA reduced the rate of tiller occurrence.Furthermore,exogenous IAA and GA3 completely inhibited growth of tiller bud,while exogenous ABA significantly slowed the growth rate of tiller bud.The growth of tiller bud was positively correlated with content of zeatin(ZT),but negatively correlated with IAA content and ratios of IAA/ZT and ABA/ZT.In contrast,the growth of tiller bud had slightly negative correlations with GA3 and ABA contents.These results suggest that IAA and ZT play a key role in regulating tiller occurrence in wheat,and exogenous hormones regulate the growth of tiller bud through changing contents of IAA and ZT and the ratios of IAA/ZT and ABA/ZT in tiller node.