White campion (Silene latifolia, Caryophyllaceae) is a classical model species for studies of sex determination and sex chromosome evolution in dioecious plants. Deletion mapping in this species revealed the presence of two Y-linked sex determining genes—the stamen promoting factor (SPF) gene and a gynoecium suppressing factor (GSF), which inspired the development of the classic ‘two genes’ model for dioecy evolution. We recently identified a Y-linked GSFY gene that encodes a CLAVATA3 homolog and causes gynoecium suppression in S. latifolia via WUSCHEL-CLAVATA feedback loop. Interestingly, the WUSCHEL homolog in S. latifolia (SlWUS1) is also sex-linked and both GSFY and SlWUS1 are located in the oldest part of the sex chromosomes, suggesting that selection to prevent recombination between these genes may have contributed to the origination of sex chromosomes in this species. The WUS-CLV3 pathway is also involved in the sexual differentiation of gynoecium development in kiwifruits and melon, indicating that this pathway plays central role in gynoecium suppression in dioecious and monoecious plants.

Streptocarpus rexii and S. grandis have been extensively studied to unravel their developmental evolution. We karyologically studied S. grandis and S. rexii, and compared their meiotic behavior with that of their F₁ hybrid. The karyotypes of the two species are very similar, however, with all the chromosomes being larger in S. grandis. In the F₁ hybrid, a greatly regular bivalent formation was observed that suggests a conserved chromosome organization between the parents. Chromosome associations with nucleoli indicated the presence of one terminal NOR locus per genome in S. grandis and of two terminal loci for S. rexii, the latter conforming to results of a previous study using fluorescent in situ hybridization. In the present study, a weak association of chromosomes in two bivalents was observed in the parents and F₁ hybrid, which may be due to the telocentric morphology of these chromosomes. We found a close correlation between the regularity in meiosis and the proportion of potentially functional pollen in the parent species. This correlation broke down in the hybrid that was found to be greatly sterile. Since the chromosome structure in the parents was similar, the late abortion in pollen formation found in the F₁ hybrid may be explained by a genetic factor, though future studies are needed here. This study adds to our knowledge of the meiotic behavior and postmeiotic pollen formation in hybrids of Streptocarpus.

Chromosome numbers of one species of Eranthemum (E. macrophyllum Wall. ex Nees) and five species of Strobilanthes [S. affinis (Griff.) Terao ex J. R. I. Wood et J. R. Benett., S. biocullata Y. F. Deng & J. R. I. Wood, S. dimorphotricha Hance, S. heteroclita D. Fang et H. S. Lo and S. pseudocollina K. J. He et D. H. Qin] in the family Acanthaceae from China have been reported for the first time. The chromosome numbers were determined as 2n=4x=44 in E. macrophyllum, 2n=2x=30 in S. affinis, S. biocullata and S. heteroclita, 2n=2x=18 in S. dimorphotricha and 2n=2x=32 in S. pseudocollina.

To understand plant evolution and diversification, information regarding chromosome number and meiotic behavior is imperative. The present study was carried out to determine the chromosome count, meiotic behavior, pollen fertility, and seed set of a medicinally important plant Peganum harmala. Two cytotypes, diploid and tetraploid are growing in western Himalaya; the diploid cytotype (2n=2x=24) is growing in Kashmir Himalaya, and the tetraploid (2n=4x=48) in Trans Himalaya, Ladakh. Chromosomes pair into perfect bivalents and segregate normally during anaphase-I and II of pollen mother cells. Pollen fertility ranged from 89.97 to 90.46% in the diploid cytotype and 88.0 to 90.0% in the tetraploid cytotype. The cytotypes identified can be exploited for restoration ecology, conservation, and sustainable development.

Indigofera santapaui Sanjappa is little-known species and reported from very few localities of the north Western Ghats. In the present investigation, somatic chromosome number (2n=16) and karyotype analysis were reported for the first time in I. santapaui. The karyotype formula was observed to be 2n=16=12m+4sm. Karyotype fell in 2B asymmetric category of Stebbins’ classification.

Cell walls in the giant-celled green alga Valonia utricularis exhibit a “crossed-fibril” type of cell wall structure, wherein cellulose microfibrils (CMFs) in the cell wall are arranged in a uniform orientation in each lamella. The CMF orientation differs by 80° to 120° between neighboring lamellae. The arrangement of the nascent CMFs deposited on regenerating protoplasts was investigated using an atomic force microscope for the first time in the organisms possessing crossed-fibril-type cell walls. At 9 h after protoplast preparation, only CMFs arranged in random orientations were observed, then CMFs arranged in parallel orientation appeared at 12 h after preparation. The parallel CMFs gradually increased until the inner cell wall surface was completely covered with CMFs in a uniform orientation at 48 h after preparation. The average size of regenerating protoplasts with parallel CMF arrangement was significantly smaller than that with the random arrangement in the specimens at 12 h after protoplast preparation.

Salvia miltiorrhiza is an important medicinal plant for its special pharmacological activity in cardiovascular and cerebrovascular diseases. The objective of this work was to develop S. miltiorrhiza autotetraploid through colchicine and to reveal their agronomic traits. For polyploidy induction of S. miltiorrhiza, seedlings at the shoot apexes stage were treated with colchicine in various concentrations [0, 0.1%, 0.2%, and 0.3% (w/v)] in three treated times (3, 5, and 7 applications). Putative autotetraploid were selected by morphological and stomatal characteristics, and their ploidy level was confirmed by flow cytometry analysis and chromosome counting. As expected, the chromosome number was 2n=2x=16 in diploids, and 2n=4x=32 in the autotetraploid. According to the results, 0.2% (w/v) of colchicine treatment 6 times can be effective for polyploidy induction in S. miltiorrhiza. The autotetraploid plants usually were accompanied by larger leaf size, stoma size, and pollen grains, but a decrease in the percentage of normal pollen. Since some autotetraploid plants showed morphological and physiological traits, antioxidant enzyme activity, wet weight, and bioactive compounds content superiorities compared to diploid plants, they can be used as germplasm materials for the breeding of S. miltiorrhiza.

Chromosomes pair with their homologues to form a bivalent in meiosis I. The formation of bivalent chromosomes, alignment on the metaphase plate, and segregation during anaphase I is critical for correct cell division and production of haploid gametes, yet exceptions to the rule of bivalent formation exist. Here, we studied the segregation of the univalent X chromosome in the two-striped plant hopper Acanalonia bivittata (Hemiptera, Auchenorrhyncha). The species identification was verified through DNA barcoding, and the chromosome number is consistent with previously published karyotypes for the species. We show that A. bivittata male primary spermatocytes have a univalent X chromosome that displays independent and delayed segregation. Univalent segregation was observed to occur after that of the autosomes during early anaphase I and was associated with the loss of microtubule connections to one spindle pole. This work contributes to our knowledge of how chromosomes that lack a pairing partner can be segregated in an environment where they are surrounded by correctly segregating bivalents.

Apteronotus include a large number of recognized species, but few have been cytogenetically studied. This study establishes the first cytogenetic description of A. ellisi collected from the upper Paraguay River basin, which presented 2n=52 chromosomes, karyotype composed of 20 metacentric, 20 submetacentric, eight subtelocentric and four acrocentric chromosomes, and fundamental number as 100 for both sexes. Heteromorphic sex chromosomes were absent. A pair of nucleolar organizing regions (NORs) was detected in the submetacentric chromosome pair 13 by silver-staining. Heterochromatic regions were observed in the long arms of the NOR-bearing chromosome pair. Besides the present data are valuable to help in understanding karyotypic evolution in Apteronotidae. Data from NORs confirmed the tendency of this family in presenting simple NORs sites, similar to the other Gymnotiformes clades. Yet, the presence of little heterochromatin can be used as cytogenetic markers for A. Ellis, and centric fusions/fissions appear to be an important mechanism in the karyotype evolution and differentiation among Apteronotus species.

The chromosome numbers and karyotypes of eight species, the subgenus Botryanthus of the genus Muscari distributed in Turkey were analyzed. These taxa are M. adilii M.B. Güner & H. Duman, M. anatolicum Cowley & Özhatay, M. bourgaei Baker, M. latifolium, J. Krik, M. inconstrictum Rech. f. M. microstomum P.H. Davis & D.C. Staurt, M. parviflorum Desf. and M. sandrasicum Karlén. Five of them (M. adilii, M. anatolicum, M. bourgaei, M. latifolium, M. sandrasicum) are endemic in Turkey. While the chromosome number of the examined taxa was generally determined as 2n=2x=18, the somatic chromosome number was determined as 2n=4x=36 in M. anatolicum and M. parviflorum. Haploid chromosome lengths varied from 26.00 µm (M. adilii) to 101.74 µm (M. parviflorum) among species. Karyotype analysis indicated that Muscari taxa generally have median point (M), median (m), submedian (sm), and subterminal (st) chromosomes. In addition, satellites were observed in two species, M. adilii and M. latifolium.

In order to study the ultrastructural changes and characteristics associated with programmed cell death (PCD) in the petals of Paeonia lactiflora during senescence, scanning electron microscopy and transmission electron microscopy were used to observe the surface and interior of perianth slices of P. lactiflora ‘Zhong Sheng Fen’ flower petals at different blooming stages. Observations indicated that PCD in parenchyma cells occurred at an early flowering stage, even though visible petal senescence was manifested during the collapse of epidermal cells at the withering stage. The epidermal cells of the perianth were fully extended at the blooming stage and had cristae on the cell surface that were continuously distributed over the long axis of cells, while different degrees of contraction of the intercellular space was observed. The progression of PCD displayed several characteristics: vacuolar membrane rupture and organelle degradation, nuclear membrane rupture and non-uniform cell wall degradation, and cell membrane rupture and changes to the cell wall, while vacuole degradation was likely a key event marking the start of PCD. TUNEL results further confirmed the occurrence of PCD during petal senescence.

Previous chromosome information for 2n=34 and 2n=38 is restricted to one species in the Asian Begonia sect. Jackia with 2n=34, and six species in sect. Platycentrum with 2n=38, respectively. We present here the first chromosome counts of two species B. sublobata and B. emeiensis with 2n=34 in respective sections of Jackia and Platycentrum and one species B. chingii with 2n=38 in sect. Reichenheimia, and the first karyotype analyses of them as well as two re-examined species of B. chitoensis and B. myanmarica with 2n=38 in sect. Platycentrum. We discussed the chromosome evolution of 2n=34 and 2n=38 in Asian Begonia sections Jackia, Platycentrum and Reichenheimia.