Bulliform Cells Research Articles

Brassinosteroid insensitive 1-associated kinase 1 (OsI-BAK1) is associated with grain filling and leaf development in rice

Brassinosteroid Insensitive 1 (BRI1)-Associated Kinase I (BAK1) has been reported to interact with BRI1 for brassinosteroid (BR) perception and signal transduction that regulate plant growth and development. The aim of this study is to investigate the functions of a rice OsBAK1 homologue, designated as OsI-BAK1, which is highly expressed after heading. Silencing of OsI-BAK1 in rice plants produced a high number of undeveloped green and unfilled grains compared to the untransformed plants. Histological analyses demonstrated that embryos were either absent or retarded in their development in these unfilled rice grains of OsI-BAK1 RNAi plants. Down regulation of OsI-BAK1 caused a reduction in cell number and enlargement in leaf bulliform cells. Furthermore, transgenic rice plants overexpressing OsI-BAK1 were demonstrated to have corrugated and twisted leaves probably due to increased cell number that caused abnormal bulliform cell structure which were enlarged and plugged deep into leaf epidermis. The current findings suggest that OsI-BAK1 may play an important role in the developmental processes of rice grain filling and leaf cell including the bulliform cells.

Diatom, phytolith, and pollen records from a 10Be/9Be dated lacustrine succession in the Chad basin: Insight on the Miocene–Pliocene paleoenvironmental changes in Central Africa

Abstract A discontinuous 200 m-long borehole drilled in the Bol Archipelago (13°N, Lake Chad) provided 25 samples, which were dated using the 10 Be/ 9 Be method and analyzed for their micro-biological content. The dating provided ages ranging from 6.3 ± 0.1 to 2.6 ± 0.1 Ma, a period contemporaneous with the Pliocene fossil localities located in the current Djurab desert of Chad (16–17°N). Well-preserved diatom assemblages first occurred at 4.7 ± 0.1 Ma and were dominated by the freshwater planktonic genera Aulacoseira and Stephanodiscus until the end of the Pliocene. This supports the recurrence of lacustrine conditions at Bol during all the Pliocene. The presence of pelite and argillaceous deposits in the core before 4.7 ± 0.1 Ma, however, suggests that the lake settled earlier, at least since 6.3 ± 0.1 Ma. The abundance of Afromontane pollen taxa at 4.2 ± 0.1 Ma and the occurrence of trapeziform polylobate phytoliths throughout the sequence suggest significant vegetation inputs from the southern highlands, while the importance of kaolinite in the clay sediments indicates a water supply predominantly from the south during the Pliocene. Phytolith assemblages are all dominated by lobate grass silica short cells and by blocky and elongate types, which attest to the presence of herbaceous-dominated vegetation around Bol and/or in the southern drainage basin during the Pliocene. This result is also supported by the pollen assemblage described at 4.2 ± 0.1 Ma, which shows highest affinity for the savanna biome. Moreover, low values for the Xerophytic grass phytolith index indicate the presence of humid-loving (mesophytic and aquatic) grass communities in this vegetation. At last, significant variations in the abundance of blocky and elongate phytoliths are indicative of local alternations of fully lacustrine and marshy conditions at Bol. Particularly between 3.6 and 2.7 Ma, the abundance of silicified bulliform cells combined with the absence of diatoms support a significant lacustrine reduction at Bol favoring the increasing of local marshy vegetation.

What drives elevational pattern of phytolith diversity in Thysanolaena maxima (Roxb.) O. Ktze? A study from the Darjeeling Himalayas

Phytolith formation in plants is commonly thought to be influenced by variations in temperature, precipitation and other environmental factors. The objective of this study is to test how variations in different climatic and edaphic factors i.e., temperature, rainfall, actual evapotranspiration (AET), potential evapotranspiration (PET), moisture index (MI) and soil pH along a tropical–temperate elevation gradient (150–2456m a.s.l.) in the Darjeeling Himalayas would influence the variability and plasticity of formation and frequencies of phytoliths in Thysanolaena maxima. Among the 16 phytolith types, frequency, diversity and morphometric sensitivity of some consistently occurring morphs viz., stomate, cuneiform bulliform, three-lobates and bilobates have been studied in detail to trace their sensitivity to changing environmental factors along the studied elevation gradient in Darjeeling. We used regression analysis to establish elevational pattern of phytolith diversity and sensitivity of T. maxima and to relate environmental factors with morphometric attributes. Frequencies of bilobate, three-lobates and stomate types increase with increasing elevation and MI, but decrease with MAT (mean annual temperature), AET, PET and soil pH. However, a reverse trend is noticed in frequency of bulliform types. Morphometric measurements show a positive correlation between dimensions of stomate, three-lobates and bilobates with MAT, AET, PET and soil pH and a negative correlation with MI. Length of bilobate shanks and dimension of bulliform cells are found to be negatively correlated with MAT, AET, PET and soil pH and positively correlated with MI; however, an opposite trend is noticed for shank width. No significant relationship is observed with rainfall, but MI, which is a measure of the water balance between rainfall and PET of an area shows significant correlation with morphometric traits. The study thus demonstrates that the diversity and morphometric attributes of T. maxima phytoliths are plastic in their response to different environmental factors.

Contribution to knowledge of foliar anatomy on Mnesithea selloana (Hack.) de Koning & Sosef (Andropogoneae-Panicoideae-Poaceae)

The aim of the present work was to analyze the foliar anatomy in lamina transverse section an in epidermis superficial view of Mnesithea selloana. Epidermic preparations and transections were carried out of the medium leaf part of sterile innovations that were conditioned and observed with optic microscope (OM) and scanning electron microscope (SEM).The histofoliar characteristics observed were: epidermic, intercostal, subsidiary, suberose, silicea and bulliform cells; and also guard cells, hairs, waxes, mesophylls, Kranz sheath, vascular bundles, sclerenchyma, colourless parenchyma and leaf margin. Epidermic observations showed that M. selloana presents a panicoid type epidermis presenting silicic cells as halteriforme, longer than wider epidermic cells with anticlinal sinuous walls, guard cells with triangular subsidiary cells and bicellular microhairs. At transecting, the foliar anatomical structure matches the description panicoid type showing that M. selloana presents clorenchymas arranged in only one series around the vascular bundles in some cases with an aditional series functioning as a bond between them. It did not presented meristematic sheath in first order bundles.

RL3(t), Responsible for Leaf Shape Formation, Delimited to a 46-kb DNA Fragment in Rice

Two mutants with rolled leaves, temporally designated as rl3(t)-1 and rl3(t)-2, were served for exploring the mechanism underlying the rolled leaf characteristic. Except for having typical rolled leaves, the plant heights and panicle lengths of rl3(t)-1 and rl3(t)-2 significantly decreased, and the seed-setting rate also decreased when compared with wild type 93-11. Cytological analysis suggested that the rolled leaf phenotype might be caused by the changes of number and size of bulliform cells. Genetic analysis indicated rl3(t)-1 is allelic to rl3(t)-2, and controlled by a recessive gene. Gene mapping result indicated that RL3(t) gene resided in a 46-kb long region governed by the sequence tag site markers S3-39 and S3-36 on rice chromosome 3. The result provides an important clue for further cloning the RL3(t) and understanding the mechanism of rice leaf development.

Adaptive components of tolerance to salinity in a saline desert grass Lasiurus scindicus Henrard

AbstractFive differently adapted natural populations of the native salt desert grass Lasiurus scindicus Henrard from Lesser Cholistan Desert (Pakistan) in South Punjab of east central Pakistan, were evaluated to examine their mechanism of adaptation to saline stress based on some key morpho–anatomical and physiological characteristics. Five ecotypes were collected from one saline site, two moderately saline sites, and two highly saline sites. Anatomical adaptations in each ecotype critically supported the physiological, but the adaptations were of specific nature depending on the type of each site's normal habitat conditions. Higher salinities resulted in increased Na+, Cl−, Mg2+, Ca2+ and K+ content in root and shoot. At root level, some specific structural modifications like increased sclerification in cortical and pith regions, endodermal thickness, and number and size of xylem vessels are vital for water conservation under osmotic stress. Several characteristics were promising for increasing the plants ability to deal with osmotic stress, including at the stem level, increased sclerification, stem area, cortical region thickness and vascular bundle area, and at the leaf level, significant structural modifications such as leaf thickness, epidermal thickness, sclerenchymatous area, cortical area, metaxylem area and bulliform cell area were promising. All these may contribute towards water conservation, which ultimately account for ecotype survival under saline–induced physiological droughts.

A detailed analysis of the leaf rolling mutant sll2 reveals complex nature in regulation of bulliform cell development in rice (Oryza sativa L.).

Bulliform cells are large, thin-walled and highly vacuolated cells, and play an important role in controlling leaf rolling in response to drought and high temperature. However, the molecular mechanisms regulating bulliform cell development have not been well documented. Here, we report isolation and characterisation of a rice leaf-rolling mutant, named shallot-like 2 (sll2). The sll2 plants exhibit adaxially rolled leaves, starting from the sixth leaf stage, accompanied by increased photosynthesis and reduced plant height and tiller number. Histological analyses showed shrinkage of bulliform cells, resulting in inward-curved leaves. The mutant is recessive and revertible at a rate of 9%. The leaf rolling is caused by a T-DNA insertion. Cloning of the insertion using TAIL-PCR revealed that the T-DNA was inserted in the promoter region of LOC_Os07g38664. Unexpectedly, the enhanced expression of LOC_Os07g38664 by the 35S enhancer in the T-DNA is not responsible for the leaf rolling phenotype. Further, the enhancer also exerted a long-distance effect, including up-regulation of several bulliform cell-related genes. sll2 suppressed the outward leaf rolling of oul1 in the sll2oul1 double mutant. We conclude that leaf rolling in sll2 could be a result of the combined effect of multi-genes, implying a complex network in regulation of bulliform cell development.

Importance of anatomical leaf features for characterization of three species of Mapania (Mapanioideae, Cyperaceae) from the Amazon Forest, Brazil

Mapania belongs to Mapanioideae, a quite controversial subfamily in Cyperaceae due to the existence of unusual characters in both reproductive and vegetative organs. The genus is represented by seven species in Northern Brazil but taxonomic valuable information related to the leaf organs is still unknown. The present study aimed the anatomical description of the leaf organs (either basal leaves or cataphylls and involucral bracts) of three representative Brazilian species of Mapania. Samples of cataphylls, basal leaves and involucral bracts were sectioned and stained for observations under light microscopy. The involucral bracts provide the most elucidative characters (ten) to distinguish the three species The basal leaves provides six distinguishing characters and are useful to M. macrophylla and M. pycnostachya, as they are absent in M. sylvatica. Mesophyll arrangement in the involucral bracts supports the circumscription of M. macrophylla and M. pycnostachya in M. sect. Pycnocephala and of M. sylvatica in M. sect. Mapania. Some features as thin-walled epidermal cells, stomata level and aerenchyma were considered to be adaptive to the humid environment in which the species occur. The translucent cells are here considered as aerenchyma precursors and a supportive function is assumed for the bulliform cells on the basal leaves and involucral bracts. No silica bodies were found which confirm it as a diagnostic character of Mapania among Hypolytreae genera.

Vegetation types and climate conditions reflected by the modern phytolith assemblages in the subalpine Dalaoling Forest Reserve, central China

This research describes modern phytolith records and distributions from subalpine surface soils in the Dalaoling Forest Reserve, and reveals its implications for local climate conditions with respect to the altitude gradient. Well-preserved phytolith morpho-types, assemblages, and climatic indices were used to study the relationship between local vegetation and climate conditions. The phytolith classification system is mainly based on the characteristics of detailed morpho-types described for anatomical terms, which are divided into seven groups: long cells, short cells, bulliform cells, hair cells, pteridophyte type, broad-leaved type, and gymnosperm type. Phytoliths originating from the Poaceae are composed of Pooideae (rondel and trapeziform), Panicoideae (bilobate, cross, and polylobate), Chloridoideae (short/square saddle), and Bambusoideae (oblong concave saddle). Based on the altitudinal distribution of the phytolith assemblages and the indices of aridity (Iph), climate (Ic), and tree cover density (D/P), five phytolith assemblage zones have revealed the five types of climatic conditions ranging from 1,169 m to 2,005 m in turn: warm-wet, warm-xeric to warm-mesic, warm-xeric to cool-mesic, cool-xeric, and cool-mesic to cool-xeric. The Bambusoideae, Panicoideae, and Chloridoideae are the dominant vegetation at the lower-middle of the mountains, while Pooideae is mainly distributed in the higher mountains. The close relationship between phytolith assembleages and changes of altitude gradient suggest that vegetation distribution patterns and plant ecology in the Dalaoling mountains are controlled by temperature and humidity conditions. Our results highlight the importance of phytolith records as reliable ecoclimatic indicators for vegetation ecology in subtropical regions.

Down-regulation of a LBD-like gene, OsIG1, leads to occurrence of unusual double ovules and developmental abnormalities of various floral organs and megagametophyte in rice.

The indeterminate gametophyte1 (ig1) mutation was first characterized to modulate female gametophyte development in maize (Zea mays). However, the function of its rice orthologue, OsIG1, remains unknown. For this, we first analysed OsIG1 localization from differential tissues in rice. Real-time quantitative PCR (qRT-PCR) and histochemical staining results demonstrated that the expression signal of OsIG1 was strongly detected in young inflorescence, moderately in mature flower and weakly in leaf. Furthermore, RNA in situ hybridization analyses exhibited that OsIG1 was strongly expressed in inflorescence meristems, floral meristems, empty-glume- and floret- primordia, especially in the primordia of stamens and immature ovules, and the micropylar side of the mature ovary. In OsIG1-RNAi lines, wrinkled blade formation was accompanied by increased leaf inclination angle. Cross-section further showed that the number of bulliform cells located between the vasculatures was significantly increased, indicating that OsIG1 is involved in division and differentiation of bulliform cell and lateral growth during leaf development. OsIG1-RNAi suppression lines showed pleiotropic phenotypes, including degenerated palea, glume-like features and open hull. In addition, a single OsIG1-RNAi floret is characterized by frequently developing double ovules with abnormal embryo sac development. Additionally, down-regulation of OsIG1 differentially affected the expression of genes associated with the floral organ development including EG1, OsMADS6 and OsMADS1. Taken together, these results demonstrate that OsIG1 plays an essential role in the regulation of empty-glume identity, floral organ number control and female gametophyte development in rice.

Leaf anatomical structures in Central European populations of the broad-leavedFestucataxa

This work deals with the leaf blade anatomical structures of the broad-leaved fescue taxa, natural populations of temperate forage grasses, collected from various habitats in Central Europe. The following anatomical features were examined and quantitatively characterised: the ribs of leaves, type of the mesophyll, number of the sclerenchyma ribs, quantity of sclerenchyma tissue, presence of the colourless cells, number of bulliform cells, stomatal complexes and presence of papilla number. It was concluded that the anatomical structures and the main leaf blade characteristics of broad-leaved fescues show several differences between the taxa of Schenodorus and Drymanthele subgenus. The populations of the Schenodorus subgenus present heterogeneous mesophyll, with radial parenchyma, and colourless cells. Strong correlations exist between the bulliform cells and the quantity of sclerenchyma and papillae. The populations of Drymanthele subgenus also present heterogeneous mesophyll, but this is not evident for every taxa and populations. The radial parenchyma and the colourless cells are not specific. There is a positive correlation between the bulliform cells and the quantity of sclerenchyma. The comparative leaf anatomical analysis, could contribute to the better understanding of taxonomic and anatomical diversity in this group.

Physiological adaptative characteristics of Imperata cylindrica for salinity tolerance

Two populations of cogongrass [Imperata cylindrica (L.) Raeuschel], one from the saline regions of the Salt Range and the other from the non-saline regions of Faisalabad were assessed for salinity tolerance on the basis of some key morphological and physiological attributes. It was hypothesized that the tolerant population from the Salt Range must have developed some specific structural modifications, which are responsible for its better survival under high salinities. These adaptive components can be effectively used in modern technologies for improving degree of tolerance of other sensitive crops. The population from the Salt Range markedly excelled the Faisalabad population in terms of growth and physiological attributes measured in this study. The Faisalabad population of I. cylindrica was unable to survive at the highest salt level (200 mM NaCl). The tolerance of the Salt Range population to salt stress was found to be related to high accumulation of organic osmotica, particularly total free amino acids and proline as well as Ca2+ in the shoot. The distinctive structural modifications in the Salt Range population were found to be enhanced succulence, well-developed bulliform cells in leaves and smaller stomatal area.

Structural and functional response to metal toxicity in aquatic Cyperus alopecuroides Rottb.

Abstract Morpho-anatomical and physiological response of Cyperus alopecuroides Rottb. (Family Cyperaceae), occurring in industrial-polluted water near Sheikhupura, Pakistan, to metal (Ni and Cd) stress were examined. Two levels (30 and 60 mg L −1 ) of each of Ni and Cd were maintained during the experiment. Growth and development were severely affected by both metals, however, Cd was more toxic than Ni, although Ni was absorbed readily by the roots and its considerable amount was translocated to aerial plant parts due to its mobile nature. In contrast, high amount of Cd were retained in the roots. Specific root physio-anatomical modifications for Ni tolerance were found result from leaf turgor potential, high accumulation of organic osmolytes, enhanced sclerification, and aerenchyma formation, while leaves were more developed bulliform cells and stellate parenchyma. Cd tolerance was found to be related to accumulation of organic osmolytes, thick epidermis and endodermis, enhanced sclerification, and stellate cell formation in stem, and well developed bulliform cells in leaves. The structural and functional response of metal toxicity were very specific in C. alopecuroides depending on the type of metal which enabled this species to survive successfully in metal-polluted wetlands.

Morphological trend analysis of rice phytolith during the early Neolithic in the Lower Yangtze

The investigation of rice domestication process is important for understanding how agriculture evolved in China. In this paper, we studied samples of rice phytoliths from the Shangshan (around c. 11,000–9000 cal. BP), Kuahuqiao (around c. 8200–7200 cal. BP) and Hemudu (around c. 7000–6500 cal. BP) periods in the lower valley of Yangtze River. Using two different techniques it was demonstrated that rice phytoliths could be separated into wild rice and domesticated varieties. Through time the percentage of wild rice phytoliths decreases while the percentage of domesticated rice phytoliths increases. The changes in morphological characteristics of double-peaked glume cells and scale-like decorations numbers of cuneiform bulliform cells indicates that human intervention likely impacted rice during the Shangshan, Kuahuqiao and Hemudu Periods. Based on morphological characteristics when classifying the rice phytoliths into wild rice and domesticated rice varieties of double-peaked glume cells, a large percentage of phytoliths could not be assigned to either a wild or domesticated variety. The large percentage of the uncertain type indicates that early domesticated rice phytolith may be neither completely wild nor fully domesticated in morphology. The result of this study indicates the evolution from wild rice to domestic rice occur between 12,000 and 7000 cal. BP.

Structural Features of Some Wheat (Triticum Spp.) Landraces/Cultivars Under Drought and Salt Stress

Seven local landraces of common and durum wheat (Triticum aestivum L. and T. durum L.) from the arid and semi-arid areas of the Sultanate of Oman were examined for specific leaf and stem structural features for water conservation. On the basis of shoot fresh and dry weights (g plant−1), degree of tolerance to drought and salt stresses in these wheat landraces/cultivars can be ranked as S-24 > J-305 > Sarraya > Senain > Cooley > MH-97 > Missani>Hamira > Shwairaa. Modifications related to water conservation were found to be high degree of sclerification, succulence in leaf and stem, low resistance to water conductance in vascular tissue, and pubescence on leaf surface. The salt and drought tolerant cultivar S-24 showed high proportion of chlorenchyma and intensive sclerification in stem structure, and well-developed bulliform cells and dense pubescence on the leaves. These modified features were poorly developed in lesser stress tolerant Omani wheat landraces like Hamira and Shwairaa. Accession Senain also showed stem succulence (solid stem), an important xeromorphic feature. Structural modifications in landrace Missani were found to be increased sclerification in vascular tissue and high number of metaxylem vessels and high proportion of parenchyma in stem, and highly developed bulliform cells in leaf. Overall, the promising anatomical traits in highly stress tolerant landraces/cultivars were chlorenchyma in stem, rigorous sclerification in parenchyma and around vascular tissue, stem and leaf succulence, and enhanced ratio of major conducting tissue.

Breaking dogmas: the plant vascular pathogen Xanthomonas albilineans is able to invade non-vascular tissues despite its reduced genome.

Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is missing the Hrp type III secretion system that is used by many Gram-negative bacteria to colonize their host. Until now, this pathogen was considered as strictly limited to the xylem of sugarcane. We used confocal laser scanning microscopy, immunocytochemistry and transmission electron microscopy (TEM) to investigate the localization of X. albilineans in diseased sugarcane. Sugarcane plants were inoculated with strains of the pathogen labelled with a green fluorescent protein. Confocal microscopy observations of symptomatic leaves confirmed the presence of the pathogen in the protoxylem and metaxylem; however, X. albilineans was also observed in phloem, parenchyma and bulliform cells of the infected leaves. Similarly, vascular bundles of infected sugarcane stalks were invaded by X. albilineans. Surprisingly, the pathogen was also observed in apparently intact storage cells of the stalk and in intercellular spaces between these cells. Most of these observations made by confocal microscopy were confirmed by TEM. The pathogen exits the xylem following cell wall and middle lamellae degradation, thus creating openings to reach parenchyma cells. This is the first description of a plant pathogenic vascular bacterium invading apparently intact non-vascular plant tissues and multiplying in parenchyma cells.

Overexpression of OsZHD1, a zinc finger homeodomain class homeobox transcription factor, induces abaxially curled and drooping leaf in rice

Leaf rolling is receiving considerable attention as an important agronomic trait in rice (Oryza sativa L.). However, little has been known on the molecular mechanism of rice leaf rolling, especially the abaxial rolling. We identified a novel abaxially curled and drooping leaf-dominant mutant from a T₁ transgenic rice line. The abaxially curled leaf phenotypes, co-segregating with the inserted transferred DNA, were caused by overexpression of a zinc finger homeodomain class homeobox transcription factor (OsZHD1). OsZHD1 exhibited a constitutive expression pattern in wild-type plants and accumulated in the developing leaves and panicles. Artificial overexpression of OsZHD1 or its closest homolog OsZHD2 induced the abaxial leaf curling. Histological analysis indicated that both the increased number and the abnormal arrangement of bulliform cells in leaf were responsible for the abaxially curled leaves. We herein reported OsZHD1 with key roles in rice morphogenesis, especially in the modulating of leaf rolling, which provided a novel insight into the molecular mechanism of leaf development in rice.

Cytological Mechanisms of Leaf Rolling in Rice

ABSTRACTModerate leaf rolling, which probably results from changes of various cells that constitute leaf blades, is an important trait for rice (Oryza sativa L.) breeding. To elucidate the cytological mechanism of leaf rolling, 46 stable mutants with inward (adaxial) or outward (abaxial) rolling phenotypes were obtained from more than 100,000 transfer DNA insertion lines in rice. Histological analyses of those mutants show that changes of number, size, and pattern of bulliform cells, sclerenchyma cells, parenchyma cells, and mesophyll cells as well as vascular bundles could lead to leaf rolling. Here, eight groups have been categorized according to their cytological characteristics in these mutants: increased bulliform cell number and area, decreased bulliform cell number and area, disordered bulliform cell number and area, partial sclerenchyma cell absence, phloem expansion, increased number of parenchyma cells, changes in multiple cell types, and parenchyma‐like cells from partial mesophyll cells. Our study demonstrates that changes in each individual cell type can result in rolled‐leaf formation.

酢浆草种子弹力传播机制初探

酢浆草(Oxalis corniculata L.)在幼嫩和成熟弹射后两个生理时期果实组织切片，并观察不同生理时期果实特征和野外测量酢浆草种子梯度弹射距离。结果表明：酢浆草的果皮在果实成熟阶段背缝线处已裂开，对种子的弹力传播作用不大。假种皮主要由泡状细胞组成，成熟过程中泡状细胞失水收缩严重，细胞间收缩不平衡产生扭转力并随着成熟过程逐渐积聚，当超过临界点后在种子尖端处裂开并翻卷，将种子以反弹形式斜抛出去。假种皮是酢浆草种子弹力传播的关键结构。种子质量与弹射关系图表明弹射距离越远，种子质量越大，且干重时比鲜重时关系更加明显，种子密度分布随传播距离增大先增后减。 The fruits of Oxalis corniculata L. were made into tissue sections respectively in their tender and mature period with paraffin method and they were observed to make the features in different physiological period. Besides, the ejecting distance was also measured. The results are as follows: The dorsal suture has been dehisced in ripening stage, so it scarcely contributes to seed transmis-sion by ejecting. Yet, aril is made up with bulliform cell, due to bulliform cell lost water severely in ripe period, tension is produced and accumulated gradually because of intercellular contracting balance. Also, the tip of seed would dehisce and turn up and the seeds would be tossed out by re-bounding when the tension beyond its critical point. Overall, aril is critical structure in seed transmission by rebounding. As chart shows ejecting distance is in direct proportion to fresh seed quality and the relationship is more obvious when dry seed is used. In addition, the density of seeds first increased and then decreased with increase of spreading distance.

Water stress-induced changes in morphology and anatomy of flag leaf of spring wheat

Flag leaves of wheat (drought hardened and non-hardened) were examined by light microscopy to determine whether the differences in leaf anatomy could be related to the known differences in dehydration tolerance. Plants exposure to water stress during tissue differentiation of flag leaves resulted in an irreversible reduction of leaf area and thickness, increased frequencies of stomata and higher number of bulliform cells with simultaneous decrease in number of intermediate veins and an increase in the share of the cell walls in total cell volume. The smaller leaf thickness was due to a diminished number of mesophyll layers and a decreased size of mesophyll cells. Such altered leaf anatomy indicated development of leaf xerophily. It was found that the irreversible changes in anatomy of wheat flag leaves play a decisive role in acquiring drought tolerance during wheat acclimation to drought.