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 F 1 hybrid. The karyotypes of the two species are very similar, however, with all the chromosomes being larger in S. grandis. In the F 1 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 F 1 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 F 1 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.

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 genes̶the stamen promoting factor (SPF) gene and a gynoecium suppressing factor (GSF), which inspired the development of the classic ʻtwo genesʼ 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.

Cell walls in the giant-celled green alga Valonia are composed of multiple lamellae and designated as “crossed-fibril” type wherein each lamella contains cellulose microfibrils (CMFs) arranged in a uniform orientation. Outer, older lamellae are thinner than inner, younger lamellae, probably because the former are extended during cell growth more so than the latter without deposition of new cell wall materials. If this hypothesis is correct, the density of CMFs in the outer lamellae should be lower than that in the inner lamellae. In the present study, the density of CMFs in the outermost lamellae of the cell wall, in various sizes of Valonia utricularis growing cells, was calculated using images obtained with an atomic force microscope, and the densities were compared among the cells of different sizes. The CMF density ranged from 0.5 to 4.0 µm−1, which is lower than that previously recorded for the innermost lamellae (more than 10 µm−1). Moreover, the CMF density was negatively correlated with the cell size indicating that spacing between neighboring CMFs was increased by the cell surface extension due to cell growth. These findings may support the abovementioned hypothesis that the outer cell wall lamellae are extended by cell growth without the deposition of new CMFs.

The genus Allium L. is in Amaryllidaceae family with approximately 900 species distributed worldwide. The key aim of this study was to examine variations among eight Iranian endemic Allium species based on genome size. The results showed that among eight Allium species examined, seven were diploid (A. sativum, A. stipitatum, A. fistolosum, A. umbellicatum, A. lenkoranicum, A. stamineum, and A. rubellum; 2n=2x=16). Interestingly, the chromosome number 2n=3x=24 was evidenced in A. atroviolaceum. Strong interspecific diversity was identified in the studied Allium genome size. The overall average genome sizes of examined species were 34.17 pg, varying from 22.24 pg in A. fistolosum to 43.80 pg in A. stipitatum. The positive and significant correlations between genome size and total chromosome volume (TCV), altitude, and latitudes indicate that the species with larger genome sizes were situated in higher sea levels and low latitudes areas. These results may provide suitable information for Allium evolutionary, genetics, and breeding studies.

To discriminate allopolyploid species from their parental species in Drosera, a comparative analysis of biseriate glandular trichomes (BGTs) of D. tokaiensis and its parental species was carried out. Because accurate identification of allopolyploid species D. tokaiensis is difficult due to showing intermediate morphologies between the parental species D. rotundifolia and D. spatulata, the species confirmation of 11 strains of four Drosera species including D. anglica were performed by determining the somatic chromosome numbers first, and then, cytomorphological details of the BGTs were characterized. Except for D. anglica, the typical form of the BGT was a biseriate structure made up of three cell pairs (consisted of six cells): head part (two apical cells), stalk part (two stalk cells), and foot part (two basal cells). In D. tokaiensis and its parental species, the BGTs stained with DAPI exhibited a single nucleus in each cell. Among 16 cytomorphological BGT characters of the three species, the maximum value of the BGT width of D. spatulata was shorter than those of the minimum values of D. rotundifolia and D. tokaiensis. A canonical discriminant analysis showed that the BGTs gave a clear separation to distinguish D. tokaiensis from its parental species. In cross-validated discriminant analysis, the individual variation of BGTs robustly predicted the species of each BGT, demonstrating species specificity for simple and accurate species identification by the cytomorphological characters.

Syzygium laetum (Myrtaceae) is an endemic species of Western Ghats. The karyomorphology is reported for the first time with mitotic chromosome number 2n=22. The karyotype formula is 2n=22=18m+4sm. The karyotype is a 2A type of the Stebbins category.

Two accessions were recognized in the species of Cousinia lactifelora Rech. f. Accession A had n=12 and accession B showed the presence of 0 to 10 B-chromosomes at various stages of meiosis in addition to n=12 chromosomes. These B-chromosomes were smaller than the A-chromosomes and there existed as univalent and bivalents. Association of B-chromosomes with A-chromosomes occurred in less than 0.5% at metaphase I. This phenomenon is reported here for the first time. Analysis of chromosome behavior at meiosis showed that the presence of B-chromosomes decreases chiasma frequency in A-chromosomes. The effects of B-chromosomes in odd and even numbers are different. Comparison between plants with B-chromosomes and plants without B-chromosomes suggested that the effect of B-chromosomes was on pollen stainability. It seems that the presence of B-chromosomes may be responsible for the reduction of pollen stainability in C. lactiflora.

The genus Medicago encompasses several significant and economically important annual and perennial taxa, each possessing distinct cytogenetical characteristics. Existing reports on chromosome numbers and karyology of the genus are quite intriguing and indicate the possible existence of underlying genetic variations. The present investigation on 18 taxa included three Lucerne varieties for the study of their chromosomal complements and karyological evolution. Twelve out of the 18 taxa analyzed were observed to be diploids with ten species having chromosome number of 2n=16 and two, Medicago constricta and M. rigidula contained 2n=14 chromosomes each. The remaining four species showed chromosome numbers of 2n=30 and 2n=32. Nucleolar organizing regions (NORs) have been a characteristic feature of the first pair of chromosomes in all the species analyzed. While the majority of the species analyzed show a basic number of x=8, the polybasic nature of the genus becomes apparent with x=7 and 8 and occurrence of polyploid series with 2n=14, 16, and 32. No heteromorphic pairs were observed in the chromosome complements of any of the analyzed species. This, along with the predominance of submetacentric chromosomes in the karyotypes validates the opinion that no significant structural changes have occurred to alter the karyotypes in the evolution of the genus. In the present study, numerical changes were encountered in M. arborea, M. scutellata, M. rugosa, and all three varieties of M. sativa.

Karyotype data, male meiosis and pollen fertility of endangered Phlomoides superba (Royle ex Benth.) Kamelin & Makhm., a plant of much medicinal, veterinary and ornamental value was studied. This study is the first report of karyotype and detailed male meiosis in the species. The species exist at the diploid level with 2n=22 chromosomes. The cells were stained with acetocarmine and a standard squash technique was followed to study karyotype and male meiosis in the species. The chromosomes size shows a gradual decrease from 5.25 to 3.42 µm with karyotype formula 2n=16m+6sm. P. superba shows an abnormal meiotic course with anomalies such as early and late disjunction, chromatin stickiness, formation of laggards, chromatin bridges, etc. affecting approximately 17.78% of the total PMCs undergoing the process of reduction division. However, high pollen fertility was seen despite such abnormalities.

A high-LET heavy-ion beam has a severe effect on survival and effectively induces chromosomal rearrangements. In this study, the effect of high-LET heavy-ion irradiation on mutation induction in the M1 generation was investigated in an inbred line of Torenia fournieri, which is a widely used horticultural plant. Dry seeds of the inbred line ‘Zairai murasaki’ were irradiated with a C-ion beam (LET: 50 keV µm−1) or Ar-ion beams (LETs: 184 keV µm−1 or 290 keV µm−1) at different doses, and then sown on 1/2 MS plates. After determining the survival rates from each irradiation condition, appropriate doses of each beam were roughly determined to produce a survival rate of 90%: 300, 75, and 50 Gy for the C-ion beam with a LET of 50 keV µm−1, Ar-ion beam with a LET of 184 keV µm−1, and Ar-ion beam with a LET of 290 keV µm−1, respectively. In the screening of branches with aberrant flowers, one and two aberrant plants were isolated from 16 and 30 M1 plants after irradiation with LETs of 184 keV µm−1 and 290 keV µm−1, respectively. However, no aberrant plants were identified in M1 plants after irradiation with a LET of 50 keV µm−1. We concluded that high-LET heavy-ion beam irradiation is effective in inducing mutations even in the M1 generation of inbred ornamental plants. This technique could be widely used for breeding ornamental plants that can be propagated vegetatively.