Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

Genotypic Variation in the Thickness of Silica Deposition on Flowering Rice Spikelets

Silicon may play an important role in regulating the transpirationrate of rice (Oryza sativa L.), particularly cuticular transpiration.The control of cuticular transpiration is important in ricespikelets because water stress at anthesis may severely disruptfertility and grain yield. Data on the quantitative variationamong rice cultivars in the thickness of the silica layer ofthe flowering spikelet were obtained in order to assess thepotential for genetic selection for silica layer thickness asa potential means for increasing spikelet resistance to waterloss. Flowering spikelets were collected from 17 genotypes and thicknessmeasurements were made of the major anatomical layers in crosssection. The silica layer of the lemma varied from 42 to 177µm among cultivars. Similar variation was observed inthe palea. Differences among cultivars were also found in thethickness of the epidermis and sclerenchyma-parenchyma layer. The total cross-sectional thickness of the lemma and palea averagedslightly over 100 µm. Total thickness was not significantlycorrelated with the length, width or product of length width.Thickness of silica deposition was significantly correlatedwith spikelet length width suggesting that these easily measuredparameters may be useful in screening for silica thickness. Oryza sativa L., rice, panicle, silicon, lemma, palea, husk     

Characteristics of Starch Grains Isolated from Mature Pepper Leaves Grown under Different Irradiances and Daylengths

The size, shape and number of starch grains have been determinedin mature pepper leaves taken from plants grown under definedconditions of daylength and irradiance. Starch grains were 0.2–7.0 µm diameter and 02–1.5µm in thickness. Grain diameter was positively relatedto daylength and the number of grains per unit leaf area inverselyrelated to daylength. Mean grain diameter was also positivelyrelated to leaf area. Analysis of starch grains from leaves having a wide range ofstarch contents showed that grain diameter was linearly relatedto leaf starch content. However, mean diameter only doubledwith a 10-fold increase in starch content. The number of grainsincreased from approximately 5 ? 10¹⁰ m^–2 of leaf to over200 ? 10¹⁰ m^–2 with increasing starch content. The totalsurface area of grains increased from less than 1.0 m² m^–2leaf to over 20 m² m^–2 leaf. Leaf starch grain shape and size are compatible with both efficientstorage as disc-shaped chloroplasts and the maintenance of hightotal grain surface area by increasing grain number more thandiameter. Possible mechanisms for the control of grain initiation,growth and degradation are suggested. Key words: Starch grains, size, shape, pepper leaves     

Anatomical and morphological parameters of leaves and leaf petioles of Actinidia deliciosa

Differences in anatomy and morphology of the kiwifruit leaves and leaf petioles might play a considerable role in the sex-determination. Three months after bud break (June), the kiwifruit leaves of both male and female plants, grown on the vegetative and generative shoots showed different leaf area (128.6 ± 13.45 cm2 in male and 104.5 ± 4.02 cm2 in female plants) and shape. The most frequently leaf shape was determined as "folium cordatum" and "folium rotundato-cordatum". Higher values of total leaf thickness of the female leaves (190 ± 3.84 μm) in comparison to male leaves (174 ± 3.52 μm) were estimated, resulting in the thicker adaxial leaf epidermis and especially in thicker palisade parenchyma in female leaves (136 ± 2.76 μm in comparison to 104 ± 1.61 μm in male leaves). Typically bifacial leaves were observed in both male and female leaves. Anomocytic stomata in hypostomatic leaves were found. The reticulate venation appears to be the main type of leaf venation. Stalked stellate multicellular trichomes on the abaxial leaf side were frequently observed in the leaves of both sexes. No important differences between male and female plants were found in the structures of vascular system in leaves and leaf petioles. Thus leaf thickness and surface morphology of adaxial leaf epidermis can be considered as important structural parameters in the sex determination. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Effect on Wheat Grain Growth of the Removal or ABA Treatment of Glumes and Lemmas

When the glumes and lemmas were removed from wheat spikeletsduring the main grain filling period the uptake of sucrose intothe subtended grains was reduced in a few hours, but the abilityto synthesize starch was not affected for several days, by whichtime a marked loss of water content had occurred. When the deglumedears were covered to maintain high humidity, the grains hada weight and water content similar to those from unprotecteddeglumed ears. The application of ABA to the glumes occasionallyhad a small short-term effect on the uptake of sucrose intothe grain, but there were no long-term effects on dry matteraccumulation despite increased glume senescence. When the glume and lemma were removed shortly after anthesisthe subtended grain grew much less than grains from intact florets,with fewer and smaller aleurone cells. The removal of the lemmafrom the third floret of the spikelet had a similar effect onthe third grain, which could be partly reversed by removal ofthe grains in the lower florets. The role of the glumes andlemmas in grain development is discussed in the light of theseresults.     

Transport of zinc and manganese to developing wheat grains

An understanding of the transport pathway used by Zn and Mn to enter developing grains may allow measures to increase the Zn and Mn content of wheat grain grown on Zn/Mn deficient soils. For this reason, transport of Zn and Mn into developing grains of wheat ( Triticum aestivum L. cv. Aroona) was investigated. Detached ears (18–22 days post-anthesis) were cultured for 48 h in a solution containing 185 kBq of ⁶⁵Zn and 185 kBq of ⁵⁴Mn. Transport of ⁶⁵Zn to the grain was unaffected by removal of glumes but was slightly reduced after the lemma was removed. Heat girdling the peduncle slightly reduced the amount of ⁶⁵Zn transported to the grain, whilst heat girdling the rachilla reduced transport of ⁶⁵Zn to the grain to a greater degree, suggesting phloem transport to the rachilla. The transport inhibitor CCCP (carbonyl cyanide m -chlorophenyl hydrazone) blocked ⁶⁵Zn transport to grain but not to lemma and glumes. Removing glumes and lemma and heat girdling the peduncle did not affect transport of ⁵⁴Mn, but transport was slightly affected by heat girdling the rachilla, indicating xylem transport. CCCP blocked transport of ⁵⁴Mn into the grain but not to lemma and glumes. It was concluded that xylem-to-phloem transfer of Zn occurs in the rachis and to a lesser extent in peduncle and lemma. The results suggest that the lemma may be an important site for phloem loading when the concentration of Zn within the xylem is high. The data also suggest that Mn was predominantly translocated to the spikelets in the xylem, but that transport to the grain was dependent upon membrane transport before entering the grain. Phloem loading of Mn into the grain vascular system may have occurred at the site of xylem discontinuity in the floral axis.     

Wheat nitrogen metabolism during grain filling: comparative role of glumes and the flag leaf

The mobilization of nitrogen (N) compounds and the roles played by glumes and the flag leaf during grain filling were studied in bread wheat (Triticum aestivum L. cv. Florida) grown under field conditions. Glumes lost twice as much of their total N content as that lost by the flag leaf between the milk and early dough stages. In the flag leaf, glumes and grains, Glu, Asp, Ser and Ala accounted for 85% of all the reductions in the free amino acid pool. Principal component analysis of free amino acid pools separated grains from the glumes and the flag leaf, suggesting grain specific regulations in the use of free amino acids in protein synthesis. In all three organs, no decrease in Gln was detected, probably due to steady glutamine synthetase (GS; EC 6.3.1.2) activities per soluble protein in both the flag leaf and glumes. Compared with the flag leaf, glumes presented relatively smaller amounts of the chloroplast GS associated isoform. This we show is due to a lower relative number of mesophyll cells in glumes as supported by the different anatomy and the cellular pattern of the GS immunolocalization. We argue that cellular distribution plays a key role in supporting metabolism to enable the various functions undertaken by glume tissue.     

生长素代谢、运输及信号转导调控水稻粒型研究进展

水稻(Oryza sativa)是世界主要粮食作物。随着我国经济飞速发展, 耕地面积逐年减少, 提高水稻总产量唯有依靠单产的增加。粒重是决定水稻产量的重要因素之一, 其遗传稳定, 受外界环境因素影响较小。粒重由粒型和灌浆程度决定, 而粒型性状包括粒长、粒宽、粒厚和长宽比。水稻种子颖壳和胚乳发育决定了粒型和粒重, 颖壳细胞的增殖和扩张限制籽粒发育, 胚乳占据成熟种子的大部分体积。而生长素调控受精后颖壳和胚乳的发育, 是调控种子发育和影响水稻产量的重要植物激素。生长素的时空分布受生长素代谢、运输和信号转导的动态调节, 以维持生长素在种子发育中的最适水平。该文综述了生长素代谢、运输和信号转导调控水稻粒型的研究进展, 以期为深入探究生长素调控水稻粒型发育机制和提高水稻产量提供线索。     

Nitrogen Redistribution during Grain Growth in Wheat (Triticum aestivum L.) : IV. Development of a Quantitative Model of the Translocation of Nitrogen to the Grain

Translocation of nitrogen was measured in wheat (Triticum aestivium L. cv SUN 9E) plants grown without an exogenous supply of nitrogen from the time that the flagleaf began to emerge, and a model of nitrogen translocation was constructed to describe translocation on one day during the linear period of grain growth. Nitrogen for grain development was derived entirely by the redistribution of nitrogen from vegetative organs. Leaves contributed 40%, glumes 23%, stem 23%, and roots 16% of the nitrogen incorporated by the grains on the fifteenth day after anthesis. Less than 50% of the nitrogen exported from leaves was translocated directly to the grain via the phloem, the rest was translocated to the roots and was cycled in the roots and exported to the shoot in the transpiration stream. Nitrogen imported by leaves and glumes via the xylem was not accumulated in these organs but was transferred to the phloem for reexport from the organs. A large proportion (60%) of the nitrogen in the transpiration stream was cycled in the glumes. The glumes were also a major source of nitrogen for grain development. It was considered likely that this organ always plays an important role in nitrogen metabolism in wheat.     

Identification of rice root proteins regulated by gibberellin using proteome analysis

Gibberellin (GA) promoted rice (Oryza sativa L.) root elongation in a concentration-dependent manner with roots grown in 0.1 µm GA₃ being 13.8% longer than controls. On the other hand, the roots of Tan-ginbozu, a semi-dwarf cultivar were 69.8% shorter in comparison with Nipponbare, a normal cultivar. Treatments with 10 µm uniconazole-P and 10 µm abscisic acid (ABA) caused decreases in root length in Tan-ginbozu by 44.6 and 79.2%, respectively. To investigate how GA influences rice root growth, proteome analysis techniques were applied. Extracted proteins were separated by two-dimensional polyacrylamide gel electrophoresis and analysed using an automated protein sequencer and mass spectrometer. Sixteen proteins show differences in accumulation levels as a result of treatment with GA₃, uniconazole-P and ABA treatment and/or the difference between the semi-dwarf cultivar, Tan-ginbozu, and normal cultivars. Among these proteins, fructose-bisphosphate aldolase (EC 4.1.2.13) increased in roots treated with GA₃, occurred in low levels in Tan-ginbozu roots, and decreased in roots treated with uniconazole-P or ABA. Moreover, roots from seedlings grown in 100 µm glucose were 9.1% longer than controls. These results indicate that increases in fructose-bisphosphate aldolase activity stimulate the glycolytic pathway and may play an important role in the GA-induced growth of roots.     

Assessment of heavy metal contamination of rice grains (Oryza sativa) and soil from Ada field,Enugu, Nigeria: Estimating the human healtrisk

The concentrations of heavy metals in rice grains and soils from Ada cultivated fields were investigated. Rice and soil samples were digested and the heavy metal concentrations determined using atomic absorption spectrophotometer. The results showed the following concentrations of metals (mg/kg): soil—Pb (4.64 ± 2.18), Cd (0.83 ± 0.83), Zn (20.26 ± 18.60), Mn (68.90 ± 19.91), Ni (3.46 ± 2.42), and Cr (21.41 ± 14.6); rice—Pb (3.99 ± 1.43), Cd (1.10 ± 0.53), Zn (65.37 ± 58.09), Mn (37.81 ± 5.82), Ni (3.12 ± 1.49), and Cr (10.87 ± 6.47). The Canadian, Nigerian and Chinese maximum allowable concentration for cadmium in soil were exceeded by 15%, 30%, and 85% of the soil samples, respectively. Heavy metals in all the rice samples evaluated were found to be above the World Health Organization (WHO) maximum permissible limit for lead, cadmium, and chromium. Strong positive and significant correlations were observed between some metal pairs in soil and rice indicating the similarity in origin. The estimated daily intakes of Pb and Cd from rice grown on the fields were higher than the safety levels established by WHO and the Joint FAO/WHO Expert Committee Food Additive, respectively. Hazard quotients and total hazard index for Pb and Cd were greater than 1. This indicates that consumption of rice from these fields will likely induce adverse health effects arising largely from Pb and Cd exposure.     

Variation in responses to boron in rice

Background and aims

Boron (B) deficiency depresses grain set and grain yield of wheat and maize while having little effect on their vegetative growth. This paper describes effects of B deficiency in rice and how these vary with planting season and variety.

Methods

Three rice varieties (KDML105, CNT1, SPR1) were grown in sand culture without (B0) and with 10 μM (B10) B added to the nutrient solution, in the cool season of 2007/08 and 2008/09 and the hot season of 2011 in Chiang Mai, Thailand (18°47′N, 98°59′E). Boron responses were measured in growth and yield parameters, pollen viability and B concentration of the flag leaf and anthers at anthesis.

Results

Grain weight was strongly depressed by B deficiency ranging from 28 % in SPR1 to 79 % in CNT1, and the yield was much lower in the cool season than in the hot season plantings. The variation in grain weight was closely associated with grain set and number of spikelets but not with shoot dry weight or tillering. Grain set was closely related to pollen viability, and both were increased with increasing anther B concentration at >20 mg B kg^?1. In addition to its adverse effect on grain set, B deficiency also depressed grain filling and weight of individual grains in rice.

Conclusions

Boron deficiency depressed rice grain yield through adverse effects on reproductive growth, panicle and spikelet formation and grain filling, in addition to grain set as in wheat and maize.     

Grain filling in relation to monocarpic senescence of wheat in varying source-sink ratios

Flag leaf removal at any stage of grain growth hastened senescence (reduction in chlorophyll content) of the sterile glumes whereas a removal of the latter did not alter senescence of the former. Kernel mass, grain mass per ear, harvest index and sink activity reduced more conspicuously by the removal of glumes than by the flag leaf removal. Removal of grains hastened senescence of the glumes only, although protein content increased at a later grain removal in the majority of source organs. Moisture contents of the developing grains were mostly reduced by the removal of either the flag leaf or the glumes, though flag leaf removal at anthesis affected it the most. Protein levels of the developing grains reduced at harvest only when the glumes were removed at anthesis but sugar levels in later phases always decreased irrespective of the time of removal and nature of the source organs.     

Single versus double pass technique for preparation of ultrathin Descemet’s stripping automated endothelial keratoplasty tissues from donated whole eyes

This study was conducted to analyze the preoperative thickness profile and endothelial rating of ultrathin Descemet’s stripping automated endothelial keratoplasty (UT-DSAEK) tissues prepared with a single versus double microkeratome pass from donated whole eyes and corresponding eye bank postoperative results. Microkeratome-assisted UT-DSAEK tissues were prepared from freshly donated whole eyes with single-pass (SP) and double-pass (DP) technique in the Central Eye Bank of Iran. Preoperative thickness profiles and endothelial cell densities of UT-DSAEK tissues were obtained from optical coherence tomography and specular microscopy, respectively, and compared between groups. Corneal perforation rates during the eye bank preparation and postoperative reports of transplanted UT-DSAEK tissues were also compared. Over a 15-month period, 342 UT-DSAEK tissues were prepared: 248 via SP and 94 with DP technique. Mean donor corneal central thickness was 610?±?58 µm with SP and 790?±?100 µm with DP technique. Mean central thickness of UT-DSAEK tissues was not statistically different between the groups (84.8?±?11.0 µm with SP and 85.1?±?10.5 µm with DP technique, P?=?0.857). Mean increase of UT-DSAEK thickness from central to pericentral and peripheral cornea was not significantly different with both techniques. Mean differences between thicknesses of 2 pericentral locations and between those of 2 peripheral locations were not statistically different in the study groups. Corneal perforation of 1.6 and 1.1% occurred in SP and DP groups, respectively. Failed graft was reported 6 months postoperatively in 4 (1.6%) cases with SP and in 1 (1.1%) case with DP technique. Preoperative thickness profiles of UT-DSAEK tissues prepared from donated whole eyes via SP technique were not significantly different from those prepared with DP, showing a symmetric increase of thickness towards peripheral locations.     

Study of radon/thoron exhalation rate,soil-gas radon concentration,and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir

In the present study, the soil-gas radon concentration was assessed at different depth intervals, i.e., 15 cm, 30 cm, 60 cm, and 100 cm from the 30 villages of Jammu &; Kashmir, India using RAD7, an electrostatic solid state alpha detector. The radon mass exhalation and thoron surface exhalation rate has also been measured in the selected 18 soil samples out of 30 of different grain sizes (i.e., 1 mm, 300 µm, 150 µm). The active radon and thoron concentrations were also assessed in the 20 villages. Both the exhalation rates and active radon/thoron concentration were measured using SMART Rn Duo, a portable radon monitor. The average values of soil-gas radon concentration were 210 ± 84 Bq m^?3, 1261 ± 963 Bq m^?3, 4210 ± 1994 Bq m^?3, and 671 ± 305 Bq m^?3 at the depth intervals of 15 cm, 30 cm, 60 cm, and 100 cm, respectively. The exhalation rate of radon and thoron from soil was found to decrease with the increase of grain size, as smaller soil particles make relatively more contribution to radon and thoron exhalations from the ground surface than larger soil particles. The measured Pearson's correlation coefficient was obtained as statistically significant between different quantities under two-tailed test.     

Dendrite Growth—Microstructure—Stress—Interrelations in Garnet Solid-State Electrolyte

This study illustrates how the microstructure of garnet solid-state electrolytes (SSE) affects the stress-state and dendrite growth. Tantalum-doped lithium lanthanum zirconium oxide (LLZTO, Li_6.4La₃Zr_1.4Ta_0.6O₁₂) is synthesized by powder processing and sintering (AS), or with the incorporation of intermediate-stage high-energy milling (M). The M compact displays higher density (91.5% vs 82.5% of theoretical), and per quantitative stereology, lower average grain size (5.4 ± 2.6 vs 21.3 ± 11.1 µm) and lower AFM-derived RMS surface roughness contacting the Li metal (45 vs 161 nm). These differences enable symmetric M cells to electrochemically cycle at constant capacity (0.1 mAh cm⁻²) with enhanced critical current density (CCD) of 1.4 versus 0.3 mA cm⁻². It is demonstrated that LLZTO grain size distribution and internal porosity critically affect electrical short-circuit failure, indicating the importance of electronic properties. Lithium dendrites propagate intergranularly through regions where LLZTO grains are smaller than the bulk average (7.4 ± 3.8 µm for AS in a symmetric cell, 3.1 ± 1.4 µm for M in a half-cell). Metal also accumulates in the otherwise empty pores of the sintered compact present along the dendrite path. Mechanistic modeling indicates that reaction and stress heterogeneities are interrelated, leading to current focusing and preferential plating at grain boundaries.     

水分胁迫对水稻籽粒蛋白质积累及营养品质的影响

以生产上广泛使用的水稻(Oryza sativa)品种‘汕优63’、‘扬稻6号’和‘武育粳3号’为材料,研究了水分胁迫对结实期水稻籽粒蛋白质积累及营养品质的影响。结果表明:正常施氮水平下,花后10~20 d的水分胁迫提高了谷氨酰胺合成酶(Glutamine synthetase,GS)和谷氨酸合酶(Glutamate synthase,GOGAT)活性,提高了籽粒自身利用无机氮合成氨基酸的能力,从而利于籽粒内蛋白质的积累,而高氮水平下,水分胁迫降低了籽粒自身合成氨基酸的能力。以重量为基数的蛋白质含有率在整个灌浆过程中呈“V”型消长,正常施氮水平下,水分胁迫明显提高了花后15 d至成熟期蛋白质含有率,而高氮水平下,水分胁迫处理的蛋白质含有率明显低于水层灌溉。与水层灌溉相比,水分胁迫提高了正常施氮水平下精米中醇溶蛋白和谷蛋白含量,但却明显降低了高氮水平下精米中醇溶蛋白和谷蛋白含量。水分胁迫对稻米中赖氨酸含量的影响因品种、植株的氮营养水平的不同而不同,水分胁迫显著降低了两种氮肥水平下‘汕优63’中赖氨酸含量,但却明显提高‘扬稻6号’中赖氨酸含量;而‘武育粳3号’于两种氮肥水平下表现恰好相反,正常施氮水平下赖氨酸含量略有升高;而高氮水平下赖氨酸含量明显降低。     

Occurrence of perfect and imperfect grains of six japonica rice cultivars as affected by nitrogen fertilization

This study aims to quantify nitrogen (N) effect on occurrence of perfect rice kernel (PRK) and imperfect grains which includes white-belly rice kernel (WBRK), white-core rice kernel (WCRK), green rice kernel (GRK), opaque rice kernel (ORK), and other imperfect grains (OTHERS). Two-year field experiments involving six japonica rice cultivars and seven N treatments were performed. The structural differences between white-belly and white-core tissues were compared using scanning electron microscope. Averaged over cultivars, grain yield increased progressively with N rate. PRK increased with N rate in 2008, but decreased with increased N rate in 2009. WBRK and WCRK decreased as N rate increased for both years. High N input resulted in higher occurrence of GRK and OTHERS for both years. Most starch granules in white-belly tissues are intact and surrounded by globular protein bodies, with many air spaces between them; while in white-core tissues, starch granules are easily broken into many single granules and no protein bodies are visible. Our results suggest that N has suppressing influence on chalky grains but favorable effect on other imperfect grains, and indicate different mechanism between WBRK and WCRK.     

Inkjet‐Printed Micrometer‐Thick Perovskite Solar Cells with Large Columnar Grains

Transferring the high power conversion efficiencies (PCEs) of spin‐coated perovskite solar cells (PSCs) on the laboratory scale to large‐area photovoltaic modules requires a significant advance in scalable fabrication methods. Digital inkjet printing promises scalable, material, and cost‐efficient deposition of perovskite thin films on a wide range of substrates and in arbitrary shapes. In this work, high‐quality inkjet‐printed triple‐cation (methylammonium, formamidinium, and cesium) perovskite layers with exceptional thicknesses of >1 µm are demonstrated, enabling unprecedentedly high PCEs > 21% and stabilized power output efficiencies > 18% for inkjet‐printed PSCs. In‐depth characterization shows that the thick inkjet‐printed perovskite thin films deposited using the process developed herein exhibit a columnar crystal structure, free of horizontal grain boundaries, which extend over the entire thickness. A thin film thickness of around 1.5 µm is determined as optimal for PSC for this process. Up to this layer thickness X‐ray photoemission spectroscopy analysis confirms the expected stoichiometric perovskite composition at the surface and shows strong deviations and inhomogeneities for thicker thin films. The micrometer‐thick perovskite thin films exhibit remarkably long charge carrier lifetimes, highlighting their excellent optoelectronic characteristics. They are particularly promising for next‐generation inkjet‐printed perovskite solar cells, photodetectors, and X‐ray detectors.     

Obtaining Large Columnar CdTe Grains and Long Lifetime on Nanocrystalline CdSe,MgZnO, or CdS Layers

CdTe solar cells have reached efficiencies comparable to multicrystalline silicon and produce electricity at costs competitive with traditional energy sources. Recent efficiency gains have come partly from shifting from the traditional CdS window layer to new materials such as CdSe and MgZnO, yet substantial headroom still exists to improve performance. Thin film technologies including Cu(In,Ga)Se₂, perovskites, Cu₂ZnSn(S,Se)₄, and CdTe inherently have many grain boundaries that can form recombination centers and impede carrier transport; however, grain boundary engineering has been difficult and not practical. In this work, it is demonstrated that wide columnar grains reaching through the entire CdTe layer can be achieved by aggressive postdeposition CdTe recrystallization. This reduces the grain structure constraints imposed by nucleation on nanocrystalline window layers and enables diverse window layers to be selected for other properties critical for electro‐optical applications. Computational simulations indicate that increasing grain size from 1 to 7 µm can be equivalent to decreasing grain‐boundary recombination velocity by three orders of magnitude. Here, large high‐quality grains enable CdTe lifetimes exceeding 50 ns.