Chromosome Behavior in Pollen Mother Cells and Pollen Grains of Different Populations of Nothoscordum frangrans Kunth

1973 ◽  
Vol 134 (4) ◽  
pp. 266-268
Author(s):  
Sumitra Sen
Keyword(s):  
Pollen Grains ◽  
Chromosome Behavior ◽  
Pollen Mother Cells ◽  
Different Populations ◽  
Mother Cells

scholarly journals Studies on the Morphology, Ontogeny and Embryology of the Flowers of Hedycarya Arborea J.R. et G. Forst. (Subfamily Monimioideae) and Laurelia Novae-Zelandiae A. Cunn. (Subfamily Atherospermoideae) of the Family Monimiaceae

2021 ◽  
Author(s):  
◽  
Frederick Bruce Sampson
Keyword(s):  
Generative Cell ◽  
Embryo Sac ◽  
Pollen Grains ◽  
Tetrad Stage ◽  
Pollen Mother Cells ◽  
The Family ◽  
Long Time ◽  
External Part ◽  
Mother Cells ◽  
And Function

<p>The inflorescences, flowers and the vascularization of floral parts of Hedycarya arborea and Laurelia novae-zelandiae were described and comparisons made with other members of the family in an attempt to determine the basic types of inflorescences, flowers and floral vascularization in the family. The vegetative, inflorescence and floral meristems of the two genera were compared. It was concluded that the vegetative apices of both had the tunica-corpus configuration typical of many other woody Ranales and other orders. The inflorescence apices were quite similar to the vegetative ones. The young floral apices are in a state of transition from a tunica-corpus to a mantle-core configuration and older floral apices had the mantle-core configuration, which is typical of the floral apices of many woody Ranales. Unusual features of the floral apices of Hedycarya and Laurelia were the lack of a pronounced rib meristem and the occurrence of relatively frequent divisions within vacuolate cells of the core. The ontogeny of the stamens of Hedycarya and Laurelia was described and comparisons were made. In both genera the micro-sporangium developed in a similar fashions: in Hedycarya 5-6 wall layers are formed inside the epidermis; in Laurelia there are 3-5 layers. Both genera had a typically thickened endothecium and a tapetum of the secretory type in which the tapetal cells become binucleate during the first meiotic division of the pollen mother cells. In Hedycarya the meiotic divisions of the pollen mother cells are of the successive type in which walls form by means of centrifugal cell plates Pollen grains remain in permanent tetrads in this genus. In Laurelia wall formation at the end of meiosis is of a modified simultaneous type, which may not have been hitherto described in the literature. Pollen grains are not in permanent tetrads. When the first division occurs in each microspore in Hedycarya, all four cells of a tetrad are at the same stage of division and the generative cell is cut off towards the distal face of the grain. Each microspore is in the two celled condition when shed. It was deduced that the generative cell is cut off against what represents a radial wall of the grain (with reference to the tetrad stage) in Laurelia. Pollen is shed in either the two or three celled condition. Comparisons were made with the development of microsporangia and male gametophytes in other woody Ranales. A study was made of the ontogeny, structure and function of the staminal appendages of Laurelia. It was found that the appendages function as nectaries, the nectar being predominantly sucrose. After a discussion of the various theories as to the morphological nature of the staminal appendages of the Laurales, it was concluded that they are morphologically staminodes. The carpels of Hedycarya and Laurelia have a basically similar ontogeny in which, as in the Lauraceae, the terminal stigmatic region develops from a solid terminal meristem in contrast to many woody Ranales in which the stigma-consists of crests which surround the external part of the cleft of the carpel. The ovules of Hedycarya and Laurelia resemble those of most other woody Ranales in being bitegmic, crassinucellate and anatropous with a monosporic 8-nucleate embryo sac of the Polygonum type. Both linear and T-shaped megaspore tetrads were found in the two genera. Laurelia has pseudocarps which develop after anthesis and enclose plumose achenes, but in Hedycarya the fruits are drupes. It was concluded that Laurelia and Hedycarya belong to two subfamilies which have been separated from each other for a long time and have undergone considerable evolution in different directions. It was also concluded that the Monimiaceae are closely related to the Lauraceae.</p>

Induction of parthenogenesis, and chromosome behavior in plants of parthenogenetic origin in cotton (Gossypium hirsutum)

Genome ◽  
1991 ◽  
Vol 34 (2) ◽  
pp. 255-260 ◽  
Author(s):  
Zhou Shi-Qi ◽  
Qian De-Qi ◽  
Cao Xiu-Yun
Keyword(s):  
Gossypium Hirsutum ◽  
Biological Treatment ◽  
Seed Set ◽  
Hibiscus Cannabinus ◽  
Root Tips ◽  
Chromosome Behavior ◽  
Flower Buds ◽  
Physical Treatment ◽  
Pollen Mother Cells ◽  
Mother Cells

Different chemical, physical, and biological treatments were applied to emasculated flower buds of cotton hybrids (Gossypium hirsutum, 2n = 4x = 52) of various genotypes with the purpose of inducing haploid parthenogenesis. Of the treatments applied, the most effective chemical treatment was 0.2% colchicine in 0.2% dimethyl sulfoxide (1.22% parthenogenetic seed set), the most effective physical treatment was high temperature (2.66% parthenogenetic seed set), and the most effective biological treatment was pollination with Hibiscus cannabinus pollen (2.33% parthenogenetic seed set). In the progeny of five plants of parthenogenetic origin, chromosome number and meiotic behavior were studied. All were mixoploids at the dihaploid level and yet set bolls almost like normal allotetraploids. Chromosome numbers ranged from 12 to 56 in the root tips within plants, with a somewhat less pronounced variation between pollen mother cells. At meiotic metaphase I in pollen mother cells 89.8% of the chromosomes were associated. Of the bivalents 23.3% showed AA pairing, 18.7% showed DD pairing, and 18.4% showed AD pairing. Trivalents and higher multivalents involved 29.4% of the chromosomes, and 10.2% were univalents. Anaphase I segregation was often unequal. Yet fertility was as high as in the allotetraploid. It is possible that the second generation was formed by parthenogenesis after restitution in the embryonic mother cells.Key words: Gossypium hirsutum, cotton, parthenogenesis, mixoploidy, meiosis fertility.

Microsporogenesis and pollen formation in lodgepole pine

1974 ◽  
Vol 52 (7) ◽  
pp. 1669-1674 ◽  
Author(s):  
Rong H. Ho ◽  
John N. Owens
Keyword(s):  
Cell Wall ◽  
Low Temperatures ◽  
Pinus Contorta ◽  
Lodgepole Pine ◽  
Pollen Grains ◽  
Chromosome Movement ◽  
Cell Wall Formation ◽  
Chromosome Behavior ◽  
Pollen Formation ◽  
Mother Cells

Microsporogenesis and pollen formation of three coastal and two interior lodgepole pine (Pinus contorta Dougl.) trees, and microstrobili of the interior trees were studied. Microspore mother cells were at pachytene when first observed and they remained at pachytene until the end of March in the interior trees and until mid-April in the coastal trees. The stages from pachytene to pollen shedding took 1 month in the coastal and interior trees. Several abnormalities were found in chromosome behavior, cell wall formation, and pollen grains. The percentage of abnormalities was higher in the interior trees than in the coastal trees. Abnormalities in chromosome movement seem to be genetically influenced and may be attributed to the large chromosomes, and to the prolonged low temperatures during meiosis and pollen formation. For interior lodgepole pine, the average number of microstrobili per shoot is 19.6 with 8.3 bud scales per microstrobilus, 93.3 microsporophylls per microstrobilus, and 2491 pollen grains per microsporangium. It is estimated that each microstrobilus produces about 465 000 pollen grains and each shoot produces about 9 million. There are about 33.5 million pollen grains per gram of dry pollen in lodgepole pine.

scholarly journals Timing of Reproductive Organs Maturity in Proterandrous Malva sylvestris L.

2017 ◽  
Vol 9 (2) ◽  
pp. 287-295
Author(s):  
Aslihan ÇETİNBAŞ-GENÇ ◽  
Meral ÜNAL
Keyword(s):  
Flower Development ◽  
Pollen Grains ◽  
Reproductive Organs ◽  
Floral Meristem ◽  
Pollen Mother Cells ◽  
Malva Sylvestris ◽  
Nucellar Tissue ◽  
Female Phase ◽  
Mother Cells ◽  
Pollen Sacs

Flower development of protandrous species Malva sylvestris L. was divided into 12 stages, as revealed by applying histological and scanning electron microscope techniques. Flower development started with the conversion of apical meristem into floral meristem. Initiation of male organ primordia started before that of female organ. Five rounded structures called corolla/androecium units differentiated from floral meristem, on which stamen primordia emerged. When pollen mother cells exist in the pollen sacs, initiation of carpels starts from floral meristem. Concurrent with the termination of meiosis in pollen mother cells, ten loculed ovary comed in view. Simultaneously with the occurrence of vacuoleted pollen grains, megaspore mother cell becomes visible in the nucellar tissue. Concominant with the existence of two celled-pollen grains, the style was formed and ovule becomes anatropous. When pollen grains are shed in male phase, ten branched stigma appeared on the upper part of the style, but receptive surface was not fully formed to accept pollen grains. Female phase is characterized by the opening of stigmatic branches with papillate receptive surface. Timing of reproductive organs maturity overlapped for a while, thus, the reproductive stragey of M. sylvestris was incomplete proterandry. 

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