Sterile Pollen Grains Research Articles

Floral deception in dioecious Actinidia polygama (Actinidiaceae) revealed by differential nitrogen investment in male organs

AbstractAnimal‐pollinated plants have evolved rewards and advertisements to attract pollinators, which learn to associate advertisements with rewards. Pollen‐collecting insects, such as bees, associate stamens with pollen (a reward) essential for brood rearing. In some dioecious plants, female flowers have stamens with sterile pollen grains to mimic male flowers. It is not yet fully understood whether females offer less nutritious pollen to pollinators in order to conserve nutrition. Here, we tested this hypothesis in a perennial vine, Actinidia polygama, which bears nectarless flowers. We quantified flower production and measured the dry mass of floral parts as well as carbon and nitrogen concentrations in floral parts and pollen in both sexes. Males produced more flowers per inflorescence and more inflorescences per shoot than females, while the dry mass of each flower was greater in females. The carbon allocation pattern was similar to that of biomass, but nitrogen allocation exhibited a remarkable reduction in sterile stamens and pollen of female flowers. In addition, as sterile pollen of females was sparse, when compared at the same volume, it was lighter than the pollen of males. Sterile pollen produced in female flowers appears to be as voluminous as that of male flowers but extremely poor in nutrients, especially in nitrogen, which clearly suggests that A. polygama females deceive pollen‐collecting pollinators for brood rearing.

Comparative study of pollen morphology and fertility in Pyrus L. species under in situ and ex situ conditions in Greater Caucasus, Azerbaijan

A number of negative changes are observed in the pollen of the vast majority of plants distributed in polluted areas: morphological immaturity or the observation of sterile pollen grains during pollination, a quantitative decrease in the total productivity of pollen, and a decrease in the germination capacity of the pollen tube.For this reason, pollen analysis is considered one of the most reliable and effective methods in environmental quality assessment as the main component of phytoindication. Light microscopy (LM) has been used to study the morphology and fertility characteristics of pollen grains in five species of Rosaceae Juss. (Pyrus L.) in detail. The study used pollen that was collected in the Republic of Azerbaijan. In this research were used Harley methods. The main purpose of the work was the comparative study of the quality and morphological characteristics of the pollen of Pyrus L. species in natural and cultural conditions.It were determined that underex situ conditions, it was found that the pollen productivity coefficient was the highest in Pyrus vsevolodii (86%), and the lowest in Pyrus georgica (72%), but under in situ conditions, the highest P.vsevolodii (89%) and the lowest P.georgica (72%) species were found in pollen.

Biomonitoring of the environment of the Arctic urbanized area using the pollen of Sorbus gorodkovii Pojark

This article investigates the content of heavy metals (Cu, Ni, V, Cd, Zn) in the reproductive organs of the Gorodkov’s rowan (Sorbus gorodkovii Pojark.) growing in the impact zone of environmentally hazardous facilities in Murmansk (CHP plants, waste incineration plant and trade sea port). The samples most contaminated by heavy metals were registered in the vicinity of the incineration plant. High concentrations of vanadium (4,2–4,8 mg/kg) and Cu, Ni, Cd, and Zn exceeding the limits of MPC are revealed in the impact zone of CHP plants operating on fuel oil. Biomonitoring of the viability of S. gorodkovii pollen showed that in all samples, the content of fertile pollen grains was reduced compared to that in the control. At the test sites of the Central and South CHP plants, the proportion of fertile pollen was 35–41 % (compared to 72 % in the control sample). The induced sterility was more than two times higher than the spontaneous sterility. High concentrations of vanadium and other toxic metals in emissions of Heating Plants have a gametocidal effect on the male gametophyte of S. gorodkovii. Groups of fertile and sterile pollen grains were selected according to their size: dwarf, normal, or hypertrophied. In the vicinity of the CHP plants, the proportion of fertile pollen of normal size decreased (62–69 %), whereas the content of dwarf (16–18 %) and hypertrophic pollen (17.4–22.7 %) increased. Sterile pollen grains were mostly dwarf (63–70 %). The results of biomonitoring indicated that CHP plants polluted the urban environment with vanadium and other toxic metals, which caused sterilization of S. gorodkovii male gametes. To improve the ecological situation in Murmansk, it is necessary to switch the thermal stations for the use of natural gas.

Overexpression of a pear B-class MADS-box gene in tomato causes male sterility

B-class MADS-box genes are sufficient for the specification of petals and stamens; however, the role of <italic>Tomato MADS-box protein 6</italic> (<italic>TM6</italic>) in seed formation in pear remains largely unknown. In this study, <italic>PbTM6a</italic> and <italic>PbTM6b</italic>, characterized as negative regulators of the response to GA₄₊₇, were identified as classic B-class MADS-box genes. Additionally, both of the genes encoding proteins carried the highly conserved MADS-box domain, and showed high expression levels in anther, petal and filament of 'Dangshansu'. Overexpression of <italic>PbTM6a</italic> in tomato reduced the number of seeds per fruit. Analysis of the anatomical structure of floral organs revealed that the reduction in seed number in transgenic fruits might be attributed to an obstacle of pollen release due to strongly formed stomium and limited ovary space of ovule development. Moreover, triphenyl tetrazolium chloride (TTC) staining and <italic>in vitro</italic> germination tests of pollen grains indicated that <italic>PbTM6a</italic> overexpression reduced pollen viability and germination rates. Reciprocal crosses showed that the reduction in seed number in transgenic fruits was dominantly caused by the decreased fertility of pollen grains. Subsequent scanning electron microscopy showed that sterile pollen grains were caused by abnormal pollen grains. Additionally, the reduced levels of jasmonic acid (JA), abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellin A3 (GA3) in transgenic stamens contributed to the development of sterile pollen. Collectively, our results reveal the role of <italic>PbTM6a</italic> genes in controlling male infertility and broaden our understanding of the mechanism underlying the function of B-class MADS-box genes in pear.

Жизнеспособность пыльцы некоторых видов древесных растений Донецкой агломерации

Data on the sterility and viability of woody plants pollen grains in the Donetsk urban agglomeration are presented. The study object was pollen samples of woody plant species used in landscaping in Donetsk such as black poplar (Populus nigra L.), white willow (Salix alba L.), horse chestnut (Aesculus hippocastanum L.), Silver birch (Betula pendula Roth). On the studied sites, it has been established that the sterility of pollen grains ranges from 16 to 44 %, and the viability ranges from 49 to 96%, which is a critical indicator indicating the inability to restore reproductive function in some of the studied species. It is statistically determined that the correlation of the studied parameters (selection points, sterility, viability) characterizes the Donetsk agglomeration as an unfavorable environment for plant life. The data obtained indicate a high degree of adaptation and resistance of tree species to technogenic impact. Indicative signs of atmospheric air pollution are determined, which are typical for the Donetsk agglomeration. Under conditions of intense technogenic load, a pattern appears in the quality change of pollen grains forming pollen anomalies. An indicator that characterizes the anatomical and morphological structure of pollen grains can be used in Donetsk conditions as a complement to other characteristics when a significant level of environmental pollution is detected.

Evaluation of pollen morphology of Passiflora species and hybrids (Passifloraceae)

Passiflora L. is a diverse genus of mostly New World species, many of which are still evolving to overcome the challenges of competition, predation, and habitat expansion. Pollen collected from 195 Passiflora L. taxa across six subgenera; Astrophea (DC.) Mast., Decaloba (DC.) Rchb., Deidamioides (Harms) Killip, Passiflora, Tetrapathaea (DC.) P.S. Green) and Tryphostemmatoides (Harms) Killip and 40 F1 hybrids (cultivars) were examined using Scanning Electron Microscopy (SEM) and low temperature SEM. Passiflora pollen grains are divided into two major morphological groups: species with three pairs (6 apertures) of colpi found in species in subgenera Astrophea, Deidamioides, Passiflora and Tryphostemmatoides, and those with six pairs (12 apertures) of colpi found in most species from subgenus Decaloba (Tetrapathea unknown). This study shows polymorphism and surface anomalies in the morphology of pollen grains of some species. Pollen from many Passiflora F1 hybrids were examined: many have a high percentage of sterile pollen grains, others in section Dysosmia DC. and Tacsonia Juss. in subgenus Passiflora recorded a minimal percentage of sterile grains. This may be a key evolutionary advantage as several species in these groups are now recorded as invasive weeds with worldwide distribution. The term, “sticky pollen” is revealed to be the pre-germination of pollen grains without stigmatic contact. The success of some invasive species to outcompete native flora and thrive in extreme environments is in part due to the evolution of their pollen, with the absence of pollen deformation following hybridization events promoting hybrid fitness. Pollen grain morphological evidence supports keeping three endemic Australian Passiflora species in subgenus Decaloba as a unique group.

Combined analysis of transcriptome and metabolome reveals that sugar, lipid, and phenylpropane metabolism are essential for male fertility in temperature-induced male sterile rice.

Photoperiod- and thermosensitive genic male sterility (PTGMS) rice is a vital germplasm resource consisting of two-line hybrid rice in which light and temperature strictly control their fertility changes. Variable environmental conditions present huge risks to the two-lines hybrid seed production. Explaining the regulatory mechanism of male fertility in rice PTGMS lines is an essential prerequisite to ensuring food security production. A group of near-isogenic lines (NILs) of a rice PTGMS line unique to this research group was used for this study. These lines have the same genetic background and regulate male fertility by responding to different temperature changes. Transcriptomic analysis revealed that 315 upregulated genes and 391 regulated genes regulated male fertility in response to temperature changes, and differentially expressed genes (DEGs) were mainly characterized in enrichment analysis as having roles in the metabolic pathways of sugar, lipid and phenylpropanoid. Electron microscopy analysis revealed that a lack of starch accumulation in sterile pollen grains induced by high temperature, with an abnormal exine development and a lack of inner pollen grains. Defective processes for sporopollenin synthesis, sporopollenin transport and pollen wall formation in sterile anthers were verified using qPCR. Targeted metabolomics analysis revealed that most lipids (phospholipids, sphingolipids and fatty acids) and flavonoids (flavones and flavanones) were upregulated in fertile anthers and involved in pollen wall development and male fertility formation, while lignin G units and C-type lignin were the major contributors to pollen wall development. The coding genes for trehalose 6-phosphate phosphatase, beta-1,3-glucanase, phospholipase D and 4-coumarate-CoA ligase are considered essential regulators in the process of male fertility formation. In conclusion, our results indicated that the expression of critical genes and accumulation of metabolites in the metabolism of sugar, lipid, and phenylpropanoid are essential for male fertility formation. The results provide new insights for addressing the negative effects of environmental variation on two-line hybrid rice production.

Hemiboea shimentaiensis S. Y. Miao, Y. Q. Li &amp; T. Chen (Gesneriaceae), a new species from northern Guangdong, China

Hemiboea shimentaiensis (Gesneriaceae), a new species from northern Guangdong, China, is described and illustrated. It is most similar to H. gamosepala, H. rubribracteata and H. malipoensis in the nearly white corolla, which appears in a few species of Hemiboea, and nearly glabrous inner base of the corolla tube. It can be easily distinguished from the latter three species by the stoloniferous habit, distinct silvery veins, glabrous corolla except for a ring of hairs inside, anther coherent along ventral face when young, but cohering apically at maturity, three separate staminodes with lateral ones resembling deformed anthers, and with few sterile pollen grains inside, to antheroids at the tips of the staminodes. The life cycle and fluctuations in the population are unknown and need further study, the conservation status of H. shimentaiensis was not assessed.

Cytology and pollen morphology of Bougainvillea glabra ‘Elizabeth Angus’, a cultivar with low pollen fertility

In this study, we analysed the pollen morphology, male gametophyte development, and callose deposition dynamics of Bougainvillea glabra ‘Elizabeth Angus’ to explore the period and mode of pollen abortion and the relationship between pollen morphology and fertility. Fertile pollen grains of ‘Elizabeth Angus’ and B. spectabilis ‘Pink Panther’ were larger than sterile pollen grains. Compared with the control ‘Pink Panther’, proportion of ‘Elizabeth Angus’ pollen grains with columellae was lower. Many abnormal phenomena were observed in pollen mother cells (PMCs) during meiosis, including laggard chromosomes, uneven chromosome separation, chromosome separation asynchrony, pentads, and micronuclei. At the early uninucleate stage, microspore development was abnormal, with deformed and shrunken pollen grains. Callose deposition was normal at meiosis and the tetrad stages of PMCs, but abnormal at the early mononuclear stage, with blocked microspore development. The complex abnormal chromosomal behaviour and delayed callose degradation in the early mononuclear stage during meiosis may account for the low pollen fertility of ‘Elizabeth Angus’. The size of the pollen grains and the morphology of the outer wall were associated with fertility; the larger pollen grains showed superior fertility, and the fertility of the pollen grains was associated with a certain number of columellae in the pollen wall. This study provides a theoretical basis for the genetic breeding of Bougainvillea.

Pollen viability as a potential trait for screening heat-tolerant wheat (Triticum aestivum L.).

High temperature during reproductive stage of winter crops causes sterility of pollen grains and reduced yield. It is essential to find the genotypes with higher pollen viability, as it is most sensitive to temperature extremes. A field study was conducted with wheat (Triticum aestivum L.) genotypes to understand the effect of high temperature on pollen viability and grain yield for 2years under timely (TS) and late sown (LS) conditions. A strong correlation was observed between higher pollen viability and higher grain yield under heat stress condition. Genotypes like K7903, HD2932, WH730 and RAJ3765 showed higher pollen viability, whereas DBW17, HUW468, RAJ4014 and UP2425 had lower pollen viability under LS condition. Further, the quantification of antioxidant enzymes activity mainly, Super oxide dismutase (SOD), Catalase (CAT), Peroxidase (POD) and Glutathione peroxidase (GPX) has showed significant variation among study genotypes. Thus, the identified high pollen viability genotypes can serve as a potential source for trait based breeding under heat stress in wheat. The present study is a first of its kind to assess more number of wheat genotypes for pollen viability and antioxidants activity under field condition. It also confirms that pollen viability can be used as a potential trait to screen genotypes for heat stress tolerance in wheat.

Male meiosis and pollen morphology in diploid Indonesian wild bananas and cultivars

Breeding of banana is hampered by its genetic complexity, structural chromosome rearrangements and different ploidy levels. Various scientific disciplines, including cytogenetics, linkage mapping, and bioinformatics, are helpful tools in characterising cultivars and wild relatives used in crossing programs. Chromosome analysis still plays a pivotal role in studying hybrid sterility and structural and numerical variants. In this study, we describe the optimisation of the chromosome spreading protocol of pollen mother cells focusing on the effects of standard fixation methods, duration of the pectolytic enzyme treatment and advantages of fluorescence microscopy of DAPI stained cell spreads. We demonstrate the benefits of this protocol on meiotic features of five wild diploid Musa acuminata bananas and a diploid (AA) cultivar banana “Rejang”, with particular attention on pairing configurations and chromosome transmission that may be indicative for translocations and inversions. Pollen slides demonstrate regular-shaped spores except “Rejang”, which shows fertile pollen grains of different size and sterile pollen grains, suggesting partial sterility and unreduced gamete formation that likely resulted from restitutional meiotic divisions.

Bioindication of toxicity and mutagenicity of the environment

The article presents the results of studying the impact of industrial emissions of enterprises of the city of Murmansk on the fertility of pollen of Sorbus gorodkovii Pojark (Gorodkov’s rowan) – an endemic species of East Fennoscandia. A low level of pollen fertility (35 – 52%) was revealed, especially in the vicinity of the local heating plants, operating on fuel oil. In the samples from all sites, a high proportion of sterile pollen grains was noted (48 – 65%). A significant increase of the proportion of sterile pollen of rowan in the vicinity of industrial enterprises of the city of Murmansk indicates the mutagenic effect of their emissions on the male generative system of S. gorodkovii and the process of gamete formation.

Interspecific hybrid confirmation in wide crosses of cotton (Gossypium spp) through morphological, cytological and molecular analysis

Interspecific triploid hybrids were developed between tetraploid cultivated species Gossypium barbadense cv. Suvin and TCB 37 and diploid wild species Gossypium armourianum. The F1 hybridity was confirmed by morphological, cytological and molecular approaches. The ploidy level of interspecific F1 hybrid was triploid and completely male sterile. Female parents Suvin and TCB 37 had erect growth habit, yellow petals, palmate leaves, green stem, thick and prominent leaf veins, but Suvin had dense yellow anthers while TCB 37 was with dense creamy anthers whereas male parent has a spreading growth habit, yellow petals, cordate leaves, reddish green stem, medium dense yellow anthers, thin leaf veins, protruded stigma and glabrous plant body. The growth habit, petal colour, leaf shape and size of interspecific F1 hybrid were intermediate. Plant stem colour, hairyness, leaf pubescence and anther colour of Gossypium armourianum were observed to be dominant as hybrid fully resembled Gossypium armourianum for these characters. Petal spot was observed in both male and female parents but F1 hybrids had different intensity of petal spot in their petals. Variable expression of petal spot, anther colour and filament colour was observed in the F1 hybrids. Gossypium barbadense cv. Suvin and TCB 37 had 52 chromosomes, Gossypium armourianum had 26 chromosomes and the interspecific F1 was with 39 chromosomes. Significant differences were observed between pollen size, pollen fertility of parents and their hybrids. The F1 interspecific hybrid having more than 97% of sterile pollen grains. Out of 6 polymorphic SSR markers between parents, 3 markers unambiguously confirmed the hybrid status of interspecific hybrid. This hybrid may serve as useful genetic resource for the transfer of jassid resistance gene to Gossypium barbadense cultivars.

Deciphering the meiotic behaviour in species of genus Artemisia from Cold Deserts of Ladakh (Jammu & Kashmir)

Present study reports the chromosome counts and meiotic analysis including microsporogenesis and pollen fertility in 10 species of the genus Artemisia from the cold deserts of Ladakh in the state of Jammu and Kashmir for the first time. We here add the chromosome record for species, A. desertorum for the first time from India which also includes the new intraspecific hexaploid cytotype (2n = 54) for A. desertorum. The study also reports the presence of B-chromosomes for A. gmelinii. The course of meiosis in most of the accessions was observed to be regular except for some individuals of A. absinthium, A. desertorum, A. gmelinii, and A. sieversiana which showed certain meiotic abnormalities in meiocytes involving cytomixis, chromatin stickiness, chromatin bridges, lagging chromosomes and late segregation of bivalents and consequently irregular sporads and sterile pollen grains. The genus Artemisia shows a considerable heterogeneity in chromosome numbers varying from 2n = 14 to 2n = 144. The genus exhibits several base numbers (x = 7, 8, 9, 11, 17) but x = 9 is regarded as the most common and favoured basic number. The next favoured base number is x = 8. On the otherhand, other basic numbers, x = 7, 11 and 17 are rather less common. The affect of polyploidy in genus evolution seems to be quite significant as 52.12 % of the species exists at various ploidy levels (3x, 4x, 5x, 6x, 8x, 10x, 12x, 14x). Aneuploidy causing chromosome variation in the genus is equally important from the existence of intraspecific aneuploid/ dysploid cytotypes.

Effects of air temperature, humidity and air pollution on fertility of birch pollen in urban environments

We studied effects of environmental factors on pollen fertility of Betula pendula Roth.) in 15 sites of the city of Barnaul (Russia, Altai Territory), differing in traffic intensity. We found that low temperature was more stressful for the development of birch pollen compared to high one. When the temperature drops below +8°C, the amount of sterile pollen in all locations significantly increased regardless of the anthropogenic load, on average exceeding 8%. With an increase in temperature of more than +10 °C, the proportion of sterile pollen also increased, but the jump was not as sharp as in cold weather. The optimum temperature for the formation of fertile pollen grains was in the range of 8–10 °С. The optimal humidity for the development of fertile pollen of B. pendula was 40–45%. The increase in air dryness led to a significant decrease in the quality of pollen grains, the proportion of sterile ones exceeded 8%. According to the transmission coefficient (Keff = 0.1514), the dominant factor in the development of sterile pollen grains of birch was the level of air pollution (concentration of carbon monoxide). Air temperature (Keff = 0.1427) and humidity (Keff = 0.1427) affected equally the quality of pollen. The proposed model makes it possible to predict the level of sterile birch pollen in the conditions of Barnaul depending on the weather conditions of vegetation and on the level of pollutants in the atmosphere.

Residues of xenobiotics in the environment and phytotoxic activity in Armenia

The article presents the results of a dynamic study (spring, summer, and fall) of the residues of certain xenobiotics such as organochlorine pesticides (OCPs), synthetic surfactants (SSs) in surface water, soil, sludge, snow and phytotoxic activity in Ararat and Lori marzes of Armenia (2016–2017). A comparative analysis of the environmental status showed that all pollutants studied such as γ-hexachlorocyclohexane (γ-HCH), 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (4,4′-DDT), and p-p′-dichlorodiphenyldichloroethylene (4,4′-DDE) were identified in Ararat marz with the average concentrations and detection rates higher than in Lori marz. The prominent contaminant was γ-HCH. The findings indicated the concentrations of OCPs below of regulatory concern. In Ararat marz an increase in the number of sterile pollen grains of certain wild plants was revealed (14.8–26.0%), compared with Lori marz with the levels within the contingent standard of 5–11%. The phytotoxic activity of soil samples from the Ararat marz studied on Avena sativa seedlings was significantly higher in the summer-fall period. These data correlated with monitoring findings showed an increase in the levels of γ-HCH, 4,4′-DDT, SS in the soil and sludge sampled in summer-fall in Ararat marz. This difference in the environmental status can be considered as the result of active agriculture in Ararat marz, whose share of contribution to a relevant branch of the economy of Armenia is two times higher than in Lori marz, 15.4% and 7.9%, respectively. Mentioned rates of agricultural production may be one of the reasons for the environmental deterioration in Ararat marz. The detection of 4,4-DDT, γ-HCH residues testifies the circulation of these formulations in the environment indicating their use in recent past and confirming their persistence. Although since the 70s of the last century the application of OCPs in the Republic of Armenia has been prohibited. The current situation may be explained by low awareness of farmers on different issues related to the safe management of pesticides. To ensure safe working conditions and raise awareness among the farmers we have developed “Recommendations on Safety requirements when working with pesticides” that are approved by the State Service for Food Safety at the Ministry of Agriculture of RA and included in the reference booklets for farmers as guiding information. Our study shows the understanding of associations between the deterioration of the environmental status and share of agriculture contribution to the economy that provides the evidence for future research programs.

Еколого-біологічна оцінка запилення та фертильність сортів фундука в умовах Правобережного Лісостепу України

Наведено результати досліджень фертильності та життєздатності пилку сортів фундука в умовах Правобережного Лісостепу України. У досліді використано свіжозібраний пилок і через кожні дві години зафіксовано початок та динаміку його проростання. Частка життєздатного пилку визначено через 24 години за кількістю пророслих пилкових зерен у 10 полях зору мікроскопа. Пророслими вважали пилкові зерна, трубки яких мали довжину не менше, ніж діаметр пилкових зерен. Використано пилковий матеріал сортів фундука Лозівський кулеподібний, Дар Павленка, Софіївський 15, Галле, Футкурамі, Черкеський-2. Проведені дослідження свідчать про те, що розміри пилкового зерна більш вирівняні та трапляються від 25,5 до 34 мікрон, за формою фертильні пилкові зерна округлі, рідко зустрічаються трикутні. Стерильні пилкові зерна відрізняються від фертильних менш інтенсивним забарвленням та мають не чітку округлу форму. Після оцінювання якості пилку видно, що частка фертильних пилкових зерен високий і становить від 95,1 % у сорту Лозівський кулеподібний до 45,4 % у сорту Футкурамі, стерильних від 52,4 до 3,5 %, а деформованих у межах 4 %. Внаслідок проведених досліджень встановлено, що для пилку фундука властива досить висока життєздатність і фертильність. Так для максимального проростання пилку оптимальним є середовище з 15 % розчину сахарози, на якому найвища частка пророслого пилку зафіксовано в сорту Лозівський кулеподібний – 69,8 %, найнижчий показник у сорту Черкеський-2-33,1 %. Збільшення концентрації сахарози призводило до зменшення кількості пророслих зерен, пилкові трубки ставали коротшими і викривленими. Найвища частка фертильності пилку спостережено в сорту Лозівський кулеподібний – 95,1 %, найнижчий у сорту Футкурамі – 45,4 %.

Pollen grain development and male sterility in the perfect flowers of Maytenus obtusifolia Mart. (Celastraceae).

Perfect flowers of Maytenus obtusifolia have partial sterility of pollen grains, resulting in collapsed and developed free microspores. However, the cellular events resulting in partial male sterility have not been determined. In pistillate flowers of this species, male sterility is related to the premature programmed cell death (PCD) in tapetum and sporogenic cells. The process occurs through autophagy via macroautophagy and massive autophagy and is associated with sporophytic cytoplasmic male sterility (CMS). Here, we characterised the development of pollen grains and investigated the cellular events that result in tapetum cells and free microspores PCD in perfect flowers, using light and transmission electron microscopy combined with the TUNEL (Terminal deoxynucleotidyl transferase mediated dUDP end-Labeling) assay and the ZIO (Zinc iodide-osmium tetroxide) method. Pollen grain development in perfect flowers was divided into eight developmental stages based on the characteristics of the pollen grains. Tapetum cells undergo PCD at the free microspore stage, through a macroautophagic process, by formation of autophagosomes and by autophagosomes giving rise to lytic vacuoles at maturity. In the final stage of PCD, massive autophagy occurs by rupture of the tonoplast. The development of viable and inviable microspores diverges at the vacuolated microspore stage, when PCD occurs in some free microspores, causing interruption of pollen development through necrosis. These events result in the observed partial male sterility. Viable microspores undergo mitosis and develop into tricellular pollen grains. Male sterility in hermaphrodite individuals is here interpreted as gametophytic CMS.

New chromosome counts and evolutionary tendencies in some dicots analyzed from Parvati Valley, Kullu district, Himachal Pradesh

The present study covers chromosome counts, male meiosis and pollen fertility in 164 species of dicots from the Parvati Valley, Kullu district, Himachal Pradesh. Gathered cytological information generates first ever chromosome counts, new diploid/polyploid cytotypes and varied chromosome counts. As many as 41 species (25%) showed intraspecific euploid cytotypes. Role of aneuploidy causing chromosomal variation is apparent from the existence of 71 species (43.29%) depicting aneuploid/dysploid cytotypes at diploid and/or polyploid levels and 114 genera showing dibasic/polybasic nature. The existence of abnormalities in several species resulted in the production of genetically imbalanced and sterile pollen grains. The viable gametes with variable chromosome numbers might have played a part in the origin of aneuploids, polyploids and species complexes. Also the non-viable gametes produced as a consequence of meiotic irregularities might have resulted in reduction of reproductive success of species thr...

First record of chromosome count and cytomixis in an endemic species ofClematis ladakhianaGrey-Wilson (Ranunculaceae) from cold deserts of Jammu and Kashmir

Meiotic investigations carried out from the cold desert regions of Ladakh (India) record the first ever chromosome count (2n = 32) and cytomixis in Clematis ladakhiana. The phenomenon of cytomixis involving chromatin transfer among 2–6 adjacent pollen mother cells (PMCs) through cytoplasmic channels was observed at different meiotic stages. The chromatin transfer resulted into hypo, hyperploid and enucleated PMCs. Although the frequency of meiocytes involved in chromatin transfer was low it induces abnormalities in chromatin and spindle activity, resulting into some pollen malformation in the form of variable sized fertile and sterile pollen grains. The Majority (86.60%) of the pollen grains observed were large sized, (86.60%) while (7.79%) are relatively small sized.