Identification of a Novel Allele of TaCKX6a02 Associated with Grain Size,Filling Rate and Weight of Common Wheat

Cytokinin oxidase (CKX) plays a crucial role in plant growth and development by reversibly inactivating cytokinin (CTK). Twenty-four primer pairs, designed from ESTs of the TaCKX genes family of common wheat, were used to identify their allelic variations associated with grain size, weight, and filling rate in 169 recombinant inbred lines (RIL) derived from Jing 411 × Hongmangchun 21. TaCKX6a02, a member of TaCKX gene family, amplified by primer pair T31–32, showed a close association with grain traits in this RIL population. Statistical analysis indicated that allelic variation of TaCKX6a02 had significant correlation with grain size, weight, and filling rate (GFR; P < 0.001) under varied environments. The TaCKX6a02-D1a allele from Jing411 significantly increased grain size, weight and grain filling rate, compared with TaCKX6a02-D1b from Hongmangchun 21. TaCKX6a02 was located on chromosome 3DS in the interval of Xbarc1119 and Xbarc1162, with a genetic distance of 1.4 cM. The location was further confirmed using Chinese Spring nulli–tetrasomic lines. A major QTL (quantitative trait locus) tightly linked to TaCKX6a02 was detected in the RIL population, explaining 17.1~38.2% of phenotype variations for grain size, weight, GFRmax and GFRmean in different environments. In addition, significant effects of variations of TaCKX6a02 on grain weight and GFR were further validated by association analysis among 102 wheat varieties in two cropping seasons. 12.8~35.1% of phenotypic variations were estimated for these genotypes. A novel 29-bp InDel behind the stop codon was detected by DNA sequence analysis between the two alleles of TaCKX6a02-D1. The gene-specific marker, TKX3D, was designed according to the novel variation, and can be used in marker-assisted selection (MAS) for grain size, weight, and GFR in common wheat.     

Light promotes an increase of cytokinin oxidase/dehydrogenase activity during senescence of barley leaf segments

Following a study of the relationship between cytokinin oxidase/dehydrogenase (CKX) and senescence in darkened barley leaf segments, we have now investigated the influence of light on the in vitro activity of CKX. Seedlings of Hordeum vulgare L. were grown for 8 d under a light/dark regime of 18 h white light and 6 h darkness. Then apical parts of 7 cm length were cut from the first foliage leaves and their bases were placed in water. In segments kept in the dark, the CKX activity measured by cleavage of N₆-(Δ₂-isopentenyl)adenine rose from 0.1 pkat (g FW)⁻¹ to 0.8 pkat (g initial FW)⁻¹ within the first 4 d of incubation. In contrast, in segments kept under the light/dark regime it reached a value of 8.6 pkat (g initial FW)⁻¹ over the same time period. The chlorophyll a content declined slightly slower during light/dark cycling than in darkness. In contrast to segments and isolated laminae, corresponding attached laminae exhibited less CKX activity after 2 d under light/dark conditions than after 2 d in the dark. The activity in attached laminae of first foliage leaves of plants growing in light/dark cycling increased strongly only when the plants were older than 4 weeks. In line with this, the CKX activity in attached laminae of flag leaves of barley growing in fields increased in a late developmental state. The senescence of darkened isolated laminae of Zea mays L. and Phragmites australis (Cav.) Trin. ex Steudel was associated with an enhancement of CKX activity too. Because in most cases a positive correlation between CKX activity and senescence was found, it is likely that the enzyme promotes senescence by destroying cytokinins, which help to keep Poaceae leaves green. Light may promote not only cytokinin degradation but also the formation of bioactive cytokinins in leaf segments.     

\Cytokinin oxidase/dehydrogenase (CKX) activity in wild and ethylene-insensitive mutant eti5 type of Arabidopsis thaliana (L.) Heynh plants and the effect of cytokinin N1-(2-chloro-4-pyridyl)-N2-phenylurea on enzymatic activity and leaf morphology

The specific activity of cytokinin oxidase/dehydrogenase (EC 1.5.99.12) (CKX) was determined in leaves of wild type (wt) and ethylene-insensitive mutant (eti5) of Arabidopsis thaliana (L.) Heynh plants. Comparative studies showed that this mutation has lower basal CKX activity than wt. Application of 4PU-30 (N¹-(2-chloro-4-pyridyl)-N²-phenylurea) resulted in decreased CKX activity in both wt and mutant plants. The treatment increased leaf blade thickness and the volume of chlorophyll-containing cells per unit leaf area in wt but these changes were not observed in the eti5 mutant. The reduction in chlorophyll “a” and “b”, as well as in carotenoids content in the treated wt tissues resulting from altered leaf morphology was not detected in eti5 plants.     

Severe water deficit-induced ethylene production decreases photosynthesis and photochemical efficiency in flag leaves of wheat

Wheat (Triticum aestivum L.) cv. Jimai22 was used to evaluate the effect of ethylene evolution rate (EER) and 1-aminocyclopropane-1-carboxylic acid (ACC) and their relations with photosynthesis and photochemical efficiency in plants well-watered (WW) and under a severe water deficit (SWD). SWD caused a noticeable reduction in the grain mass. The marked increases in both EER and the ACC concentration were observed under SWD; it was reversed effectively by exogenous spermidine (Spd) or amino-ethoxyvinylglycine (AVG). Thermal images indicated that SWD increased obviously the temperature of flag leaves, mainly due to the decrease in transpiration rate under SWD. Exogenous Spd or AVG decreased to some extent the temperature of the flag leaves. The strong decline in photosynthetic rate (P _N) and stomatal conductance as well as the photodamage of PSII were also observed under SWD after 14 and 21 days after anthesis (DAA). Intercellular CO₂ concentration was reduced at 7 DAA, but slightly increased at 14 and 21 DAA under SWD, indicating that the decreased P _N at 7 DAA might result from stomatal limitations, while the decline after 14 and 21 DAA might be attributed to nonstomatal limitations. Correlation analysis suggested that EER and ACC showed negative relations to photosynthesis and photochemical efficiency. Data obtained suggested that the effects of SWD were mediated predominantly by the increase in EER and ACC concentration, which greatly decreased the leaf photosynthesis and photochemical efficiency, and, therefore, reduced the grain mass. Application of Spd or AVG reduced the EER and ACC, and thus positively influenced photosynthesis and photochemical efficiency under SWD.     

冷型小麦旗叶衰老和活性氧代谢特性研究

以典型的冷型小麦和暖型小麦为试验材料,研究了同一环境背景下不同温度型小麦开花后的旗叶衰老和活性氧代谢特性。结果表明,与暖型小麦相比,冷型小麦籽料灌浆期旗叶叶绿素和可溶性蛋白质含量下降缓慢、含量高,整个业粒形成和灌浆期ＭＤＡ积累速度慢、含量低,籽粒灌浆期防御活性氧伤害的关键性保护酶（ＳＯＤ、ＣＡＴ和ＰＯＤ）活性下隆幅度小,灌浆中后期活性水平高。由此认为,小麦旗叶衰老和活性氧代谢特性与其温度型的归属关     

Contribution of the wheat (Triticum aestivum L.) flag leaf to grain yield in response to plant growth regulators

In West-Europe, intensive cereal management uses plant growth regulators (PGRs) especially for wheat. A green-house experiment compared the effects of two PGRs on flag leaf characteristics and yield of winter wheat. Chlormequat chloride + choline chloride (CCC) and chlormequat chloride + choline chloride + imazaquin (CCC+I) were applied to winter wheat at growth stage 5 (Feekes Large scale). CCC and CCC+I significantly increased flag leaf surface area at anthesis. Both treatments also enhanced chlorophyll content of the main stem flag leaf. The grain filling period was extended with PGR application by 2 days. CCC and CCC+I significantly increased net CO₂ assimilation rates during the flag leaf life. No effects of PGR spraying were observed on the pattern of ¹⁴C labelled assimilate distribution. Increased grain yield was due to the increase in average grain weight. The results indicate that PGR treatments increased flag leaf contribution to grain filling. The addition of imazaquin (I) to chlormequat (CCC) improved the effects of CCC.     

Influence of reproductive organs on plant senescence in rice and wheat

The chlorophyll and protein contents of the flag, second and third leaves gradually decreased during the reproductive development of rice (Oryza sativa L. cv. Rasi) and wheat (Triticum aestivum L. cv. Sonalika) plants, whereas proline accumulation increased up to the grain maturation stage and slightly decreased thereafter. In rice plant, the rate of decrease in chlorophyll and protein and increase in proline level were higher in the flag leaf than in the second leaf. It was opposite in wheat plant. The export of [³²P]-phosphate from leaves to grains gradually increased reaching a maximal stage at the grain development stage, and then declined. The export of this radioisotope was greater in rice than in wheat. Removal of panicle at the anthesis and grainfilling stages delayed leaf senescence of rice plant, while in wheat the ponicle removal at any stage did not have a marked effect on delaying leaf senescence. The contents of chlorophyll and protein of glumes were higher in wheat than in rice. The variation of such source-sink relationship might be one of the possible reasons for the above effect on leaf senescence.     

Heat susceptibility of grain filling in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) linked with rapid chlorophyll loss during a 3-day heat treatment

Brief heat events (1–3 days, >30 °C) commonly reduce wheat (Triticum aestivum L.) grain size and consequently yield. To identify mechanisms of tolerance to such short heat events, 36 wheat genotypes were treated under day/night temperatures of 37 °C/27 °C for 3-days in a growth chamber, at 10 days after anthesis, and a range of developmental, chlorophyll and yield-related traits monitored. The degree of flag leaf chlorophyll loss during the treatment was the variable that showed the highest correlation to grain weight loss (r = 0.63; p < 0.001), identifying chlorophyll stability during this brief period as a potential determinant or indicator of grain weight stability under heat. Variables summarizing the combined during- and post-heat chlorophyll losses showed similar or lower correlations with heat tolerance of grain filling, despite the fact that genotypes varied in their ability to resume normal chlorophyll loss rates after the heat treatment. Additionally, heat tolerance of grain size showed no correlation with grain filling duration or traits relating to utilization of stem carbon reserves under heat stress. Measurement of chlorophyll loss over a forecasted heat wave was thereby identified as a potential basis for developing tools to help breeders select heat tolerant genotypes.     

Comparison of the photosynthetic characteristics in the pericarp and flag leaves during wheat (Triticum aestivum L.) caryopsis development

The pericarp of cereal crops is considered a photosynthetically active tissue. Although extensive studies have been performed on green leaves, the photosynthetic role of the pericarp in cereal caryopsis development has not been well investigated. In the present study, we investigated the anatomy, ultrastructure, chlorophyll (Chl) fluorescence, and oxygen evolution of the pericarp during caryopsis ontogenesis in field wheat (Triticum aestivum L.). The results showed that wheat pericarp cross-cells contained Chl; the grana stacks and thylakoid membranes in the cross-cells were more distinct in the pericarp than those in the flag leaves as shown by transmission electron microscopy. Chl fluorescence revealed that the photosynthetic efficiency, which was indicated by values of maximum efficiency of PSII photochemistry and effective PSII quantum yield, was lower in the pericarp compared to that of the flag leaf eight days after anthesis (DAA), whereas similar values were subsequently observed. The nonphotochemical quenching values were lower from 8–16 DAA but significantly increased in the pericarp from 24–32 DAA compared to the flag leaf. The oxygen evolution rate of the flag leaves was consistently higher than that of pericarp; notably, isolated pericarps released more oxygen than intact pericarps during caryopsis development. These results suggest that the pericarp plays a key role in caryopsis development by performing photosynthesis as well as by supplying oxygen to the endosperm and dissipating excessive energy during the grain-filling stages.     

Changes in the Chlorophyll Content and Cytokinin Levels in the Top Three Leaves of New Plant Type Rice During Grain Filling

This paper reports the ways that the differences in leaf senescence are related to grain filling, grain yield, and the dynamics of cytokinins (CKs) in the top three leaves of four field-grown new plant type (NPT) rice, a tropical japonica developed at the International Rice Research Institute, Philippines, to increase the yield potential of rice. The chlorophyll content in leaves decreased from flowering to maturity in all the NPT lines, whereas the grain filling percentage was higher in the fast-senescing NPT line than in slow-senescing NPT line. Grain yield was positively correlated with senescence in the flag leaf. Rapid changes in the CK levels were recorded in the leaves of the fast-senescing line, whereas the CK levels were relatively stable in leaves of the slow-senescing line, suggesting that the dynamics of CKs in the fast-senescing line are vital for fast senescence. There were no significant changes in bioactive CKs, CK O-glucosides (storage CKs), and cis-zeatin derivatives in different leaves of the slow-senescing NPT line between 0 and 3 weeks after flowering, suggesting that the content of these CKs is relatively stable during grain filling. A progressive increase in levels of bioactive CKs was positively correlated with gradual accumulation of CK N-glucosides (inactive CKs) in the top three leaves of the slow-senescing NPT line, whereas the decrease of bioactive CKs in the flag leaf of the fast-senescing line was accompanied by accumulation of CK O-glucosides. These results suggest that there is a higher rate of biosynthesis and/or import of bioactive CKs as well as their turnover which may favor delay of leaf senescence in the slow-senescing NPT line.     

FACE条件下大气O3浓度增高对小麦花后剑叶显微结构的影响

2008-2009年,应用FACE研究平台,采用烟农19、扬麦16、嘉兴002和扬辐麦2号4个小麦品种,以O3自然浓度为对照,研究了大气O3浓度增高50％对不同基因型小麦剑叶显微结构、叶绿素含量和粒重的影响.结果表明:在开花期,大气O3浓度增高对小麦产生轻微伤害,剑叶的叶肉细胞和叶绿体结构开始遭到破坏,基粒片层断裂并且开始松散;花后21 d,与对照的叶片微结构差异显著增大,剑叶内膜系统基本解体,叶绿体基本解散,基粒片层消失,加速了剑叶的衰老进程,剑叶的叶绿素含量、净光合速率和成熟期粒重均低于对照.小麦剑叶微结构和光合功能对大气O3浓度增高的响应存在明显的基因型差异,嘉兴002对O3胁迫的耐受性较好,而扬辐麦2号对O3胁迫的反应较敏感.     

FACE条件下大气O3浓度增高对小麦花后剑叶显微结构的影响

2008-2009年,应用FACE研究平台,采用烟农19、扬麦16、嘉兴002和扬辐麦2号4个小麦品种,以O₃自然浓度为对照,研究了大气O₃浓度增高50%对不同基因型小麦剑叶显微结构、叶绿素含量和粒重的影响.结果表明： 在开花期,大气O₃浓度增高对小麦产生轻微伤害,剑叶的叶肉细胞和叶绿体结构开始遭到破坏,基粒片层断裂并且开始松散;花后21 d,与对照的叶片微结构差异显著增大,剑叶内膜系统基本解体,叶绿体基本解散,基粒片层消失,加速了剑叶的衰老进程,剑叶的叶绿素含量、净光合速率和成熟期粒重均低于对照.小麦剑叶微结构和光合功能对大气O₃浓度增高的响应存在明显的基因型差异,嘉兴002对O₃胁迫的耐受性较好,而扬辐麦2号对O₃胁迫的反应较敏感.     

Pre-anthesis high-temperature acclimation alleviates damage to the flag leaf caused by post-anthesis heat stress in wheat

The objective of this study was to investigate the effect of pre-anthesis high-temperature acclimation on leaf physiology of winter wheat in response to post-anthesis heat stress. The results showed that both pre- and post-anthesis heat stresses significantly depressed flag leaf photosynthesis and enhanced cell membrane peroxidation, as exemplified by increased O₂⁻ production rate and reduction in activities of antioxiditave enzymes. However, under post-anthesis heat stress, plants with pre-anthesis high-temperature acclimation (HH) showed much higher photosynthetic rates than those without pre-anthesis high-temperature acclimation (CH). Leaves of HH plants exhibited a higher Chl a/b ratio and lower chlorophyll/carotenoid ratio and superoxide anion radical release rate compared with those of the CH plants. In addition, antioxidant enzyme activities in HH plants were significantly higher than in CH. Coincidently, expressions of photosythesis-responsive gene encoding Rubisco activase B (RcaB) and antioxidant enzyme-related genes encoding mitochondrial manganese superoxide dismutase (Mn-SOD), chloroplastic Cu/Zn superoxide dismutase (Cu/Zn-SOD), catalase (CAT) and cytosolic glutathione reductase (GR) were all up-regulated under HH, whereas a gene encoding a major chlorophyll a/b-binding protein (Cab) was up-regulated by post-anthesis heat stress at 10 DAA, but was down-regulated at 13 DAA. The changes in the expression levels of the HH plants were more pronounced than those for the CH. Collectively, the results indicated that pre-anthesis high-temperature acclimation could effectively alleviate the photosynthetic and oxidative damage caused by post-anthesis heat stress in wheat flag leaves, which was partially attributable to modifications in the expression of the photosythesis-responsive and antioxidant enzymes-related genes.     

Maturation in Larch : II. Effects of Age on Photosynthesis and Gene Expression in Developing Foliage

The effect of maturation on the morphological and photosynthetic characteristics, as well as the expression of two genes involved in photosynthesis in the developing, current year foliage of Eastern larch (Larix laricina [Du Roi]) is described. These effects were observed on foliage during the third growing season after grafting of scions from trees of different ages onto 2 year old rootstock. Specific leaf weight (gram dry weight per square meter), leaf cross-sectional area (per square millimeter), and chlorophyll content (milligram per gram dry weight) all increase with increasing age in long shoot foliage from both indoor- and outdoor-grown trees. Net photosynthesis (NPS) (mole of CO₂ per square millimeter per second) increases with age on indoor- but not outdoor-grown trees. NPS also increases with increased chlorophyll content, but outdoor-grown scions of all ages had higher chlorophyll content, and chlorophyll does not appear to be limiting for NPS outdoors. To extend these studies of maturation-related differences in foliar morphology and physiology to the molecular genetic level, sequences were cloned from the cab and rbsS gene families of larch. Both cab and rbcS gene families are expressed in foliage but not in roots, and they are expressed in light-grown seedlings of larch but only at very low levels in dark-grown seedlings (~2% of light-grown seedlings). Steady-state cab mRNA levels are relatively higher (~40%) in newly expanding short shoot foliage from juvenile plants compared to mature plants. Unlike cab, the expression of the rbcS gene family did not seem to vary with age. These data show that the maturation-related changes in morphological and physiological phenotypes are associated with changes in gene expression. No causal relationship has been established, however. Indeed, we conclude that the faster growth of juvenile scions reported previously (MS Greenwood, CA Hopper, KW Hutchison [1989] Plant Physiol 90: 406-412) is not due to increased NPS or cab expression. Long shoot foliage is the dominant foliar type on young trees and its lower specific leaf weight will permit production of more photosynthetic surface area per unit of leaf biomass.     

播种量和施氮量对垄沟覆膜栽培冬小麦花后生理性状的影响

为协调冬小麦个体与群体间的关系,充分发挥旱作条件下垄沟栽培优势,以冬小麦品种小偃22为材料,采用二元二次正交旋转组合设计,通过田间试验研究了垄下集中施肥、垄上覆膜、膜际种植模式下播种量和施氮量对冬小麦花后生理性状的影响.结果表明： 花后叶面积指数、旗叶叶绿素含量和净光合速率均随施氮量的增加而增加.灌浆前中期叶面积指数随播种量的增加呈先增后稳的趋势;灌浆后期叶面积指数随播种量的增加而降低.随播种量的增加,旗叶的叶绿素含量和净光合速率降低,单株产量呈先减少后增加的趋势.适宜的播种量可以协调个体与群体间的矛盾,而适量增施氮肥有利于花后小麦生理性状的改善和产量的提高.在供试条件下,小偃22在播种量112.5 kg·hm-2与施氮量180～222 kg N·hm-2配置时,个体与群体的关系比较协调,花后叶面积指数较高,群体结构适宜,而且旗叶叶绿素含量、净光合速率和单茎产量较高,能获得高产.     

播种量和施氮量对垄沟覆膜栽培冬小麦花后生理性状的影响

为协调冬小麦个体与群体间的关系,充分发挥旱作条件下垄沟栽培优势,以冬小麦品种小偃22为材料,采用二元二次正交旋转组合设计,通过田间试验研究了垄下集中施肥、垄上覆膜、膜际种植模式下播种量和施氮量对冬小麦花后生理性状的影响.结果表明:花后叶面积指数、旗叶叶绿素含量和净光合速率均随施氮量的增加而增加.灌浆前中期叶面积指数随播种量的增加呈先增后稳的趋势;灌浆后期叶面积指数随播种量的增加而降低.随播种量的增加,旗叶的叶绿素含量和净光合速率降低,单株产量呈先减少后增加的趋势.适宜的播种量可以协调个体与群体间的矛盾,而适量增施氮肥有利于花后小麦生理性状的改善和产量的提高.在供试条件下,小偃22在播种量112.5 kg hm-2与施氮量180 ～222 kg N·hm-2配置时,个体与群体的关系比较协调,花后叶面积指数较高,群体结构适宜,而且旗叶叶绿素含量、净光合速率和单茎产量较高,能获得高产.     

Delayed wheat flag leaf senescence due to removal of spikelets is associated with increased activities of leaf antioxidant enzymes,reduced glutathione/oxidized glutathione ratio and oxidative damage to mitochondrial proteins

Removal of reproductive ‘sink’ i.e. spikelets from wheat at anthesis delays the rate of flag leaf senescence. In this work, the antioxidant defense was studied in the flag leaf of Triticum aestivum cv. Kalyansona plants showing normal (S + plants) and delayed senescence via removal of spikelets (S? plants). This was done by measurement of metabolites and activities of enzymes such as superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. S? plants had higher reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and antioxidant enzyme activities than the control plants and the differences were apparent from 21 days after anthesis (DAA). The removal of the reproductive sink led to an increased antioxidant defense which may be contributing towards the delayed flag leaf senescence in wheat. Chloroplasts and mitochondria, important sources of ROS, were isolated at two stages representing early (7 DAA) and late (21 DAA) senescence. Oxidative damage to proteins was studied in these organelles in relation to SOD and APX. Mitochondria had higher levels of damaged proteins than chloroplasts at 7 DAA in both S+ and S? plants. Higher damage was related to the lower antioxidant enzyme levels of SOD and APX in mitochondria as compared to chloroplasts.     

Cloning and characterization of <Emphasis Type="Italic">Tabas1</Emphasis>-<Emphasis Type="Italic">B1</Emphasis> gene associated with flag leaf chlorophyll content and thousand-grain weight and development of a gene-specific marker in wheat

The chloroplast photosystem of flag leaves contributes the largest proportion of photosynthates to grain in crops and consequently affects grain weight. The plant 2-Cys peroxiredoxin BAS1 is involved in chlorophyll protection against chloroplast damage. In the present study, we cloned a Tabas1 gene in common wheat (Triticum aestivum L.), comprising seven exons and six introns with a complete sequence of 2847 bp and an open reading frame of 789 bp. The gene was located on chromosome 2B, and designated Tabas1-B1. A codominant gene-specific marker TaS1 was developed based on a 1-bp InDel (-/A) in the second intron of Tabas1-B1. Two alleles, Tabas1-B1a and Tabas1-B1b, at the Tabas1-B1 locus were identified by TaS1. Linkage and quantitative trait locus (QTL) mapping indicated that Tabas1-B1 was linked to Xcfa2278 (5.23 cM) and Xbarc167 (10.38 cM) on chromosome 2BL. A stable QTL co-segregating with Tabas1-B1 explained 9.0–19.2 % of phenotypic variations for chlorophyll content (ChlC) and 9.5–15.5 % for thousand-grain weight (TGW), respectively, across three environments. Association analysis further indicated a significant and positive effect of Tabas1-B1a on the ChlC of flag leaf post-anthesis and TGW in two populations across four environments. Geographic distribution analysis suggested a slightly higher frequency of Tabas1-B1a than Tabas1-B1b in the main wheat-growing regions of China. Selection of Tabas1-B1a may increase grain weight in wheat breeding.     

Chlorophenoxyacetic acid and chloropyridylphenylurea accelerate translocation of photoassimilates to parthenocarpic and seeded fruits of muskmelon (Cucumis melo)

We compared the effect of p-chlorophenoxyacetic acid (p-CPA) and 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) on parthenocarpic and seeded muskmelon (Cucumis melo) fruits in regards to fruit development and the transport of photoassimilates from leaves exposed to ¹⁴CO₂ to the developing fruits. Ten days after anthesis (DAA), the fresh weight, total ¹⁴C-radioactivity and contents of ¹⁴C-sucrose and ¹⁴C-fructose were higher in the CPPU-induced parthenocarpic fruits than in seeded fruits. However, at 35 DAA, fresh weight and sucrose content in mesocarp, placenta and empty seeds of the parthenocarpic fruits were lower than in seeded fruits. Also, total ¹⁴C-radioactivity and ¹⁴C-sugar content of the parthenocarpic fruits were lower as well as the translocation rate of ¹⁴C-photoassimilates into these fruits. Application of p-CPA to the parthenocarpic fruits at 10 and 25 DAA increased fresh weight and sugar content. Moreover, these treatments elevated the total ¹⁴C-radioactivity, ¹⁴C-sucrose content and the translocation rate of ¹⁴C-photoassimilates. The ¹⁴C-radioactivity along the translocation pathway from leaf to petiole, stem, lateral shoot and peduncle showed a declining pattern but dramatically increased again in the fruits. These results suggest that the fruit's sink strength was regulated by the seed and enhanced by the application of p-CPA.     

基于光谱变化特征的小麦叶片不同功能期监测研究

为了探讨小麦叶片不同功能期光谱变化特征与叶绿素含量之间的关系,以4个小麦杂交组合基因型为试验材料,对不同生长发育期的旗叶进行光谱和叶绿素测量,并采用线性外推法计算其红边位置.结果表明：在近红外区（750 nm～850 nm）和可见光区（500 nm～600 nm）处,从抽穗期到扬花期小麦旗叶光谱反射率呈现上升趋势,到灌浆期开始下降.其叶绿素含量也是先上升,进入灌浆期后开始下降.建立旗叶4个不同功能期4月25日、5月1日、5月6日和5月11日叶绿素含量与其红边位置线性回归模型,其R2分别为0.5893、0.8842、0.9379和0.7258,均达极显著水平,表明此模型可用于叶片叶绿素含量无损监测.