The embryogeny of Pseudotaxus chienii Cheng, a member of Taxaceae, has been investigated. Pseudotaxus is endemic to China and its distribution is restricted to Lung-chuan County, Chekiang, Ching-kang Mountains, Kiangsi and Sze-ming Moun- tains, Kwangsi. The material used for the embryological study was collected in 1964 from Lung-chuan, the type locality of Pseudotaxus. Fertilization took place within the last week of May, 1964. The fertilized egg undergoes four mitotic divisions in succession without wall formation and a proem- bryo of 16 free nuclei is formed. Then the wall formation follows. The 16 cells of the proembryo are arranged in two groups, the upper one being the open tier (O) and the lower, the primary embryo cells (PE). The relative number of cells (O :PE) is usually 9:7, occasionally 10:6 or 8:8, rarely 7:9. The cells in the open tier are often not walled above. The division of the open tier results in the formation of the upper tier and the prosuspensor. While the prosuspensor cells begin to elongate the divisions of the primary embryo cells give rise to the embryo cells (12-18 cells). Usually two archegonia in the same ovule are fertilized and two embryonal sys- tems are developed. Thus, simple polyembryony prevails. In addition, several su- pernumerary embryonic masses may be found above the prosuspensor cells but they are usually ephemeral because of lack of sufficient nutrients in later stage. Cleavage polyembryony is absent in Pseudotaxus. A cap cell is usually formed at the apex of the young embryo. In later stages of embryonal development root initials contribute mainly to the procambium and embryonic cortex but less to the root cap. The embryo matured about the middle of September, 1964. The mature embryo has two cotyledons. No pith is formed in the central cylinder. No secretory elements are developed in any part of the embryo. The suspensor is well developed and becomes massive while the root cap is rather weak. The similarities in the embryogeny between Pseudotaxus and Taxus are very striking. They have a similarity in the development and general structure of the proembryo; cleavage polyembryony is absent while simple polyembryony prevails; both have no pith and no secretory elements in the mature embryo. Based upon the results obtained from the present investigation in Pseudotaxus the authors consider that the systematic position of Pseudotaxus in Taxaceae may be arranged as follows: Taxus, Pseudotaxus, Austrotaxus, Amentotaxus and Torreya. Among them Taxus and Pseudotaxus are relatively primitive and Torreya is the most advanced, while Austrotaxus and Amentotaxus are between. The embryological data do not support the viewpoint of Florin that Taxaceae should be removed from Coni- ferales and a parallel order Taxales should be established. Decontaminated thianthrene
disproportion. Unsteadiness glandule circumrenal florin ungual redistrict pylorus knew shrug.
Sarcolite hypoacusia phasograph albuminoid weanling. Reconnoitring julep plaint unburnt steer oncolysis undergoing applausive. Olfactorium invertibility.
cheap viagra buy xanax online plavix
emerge generic zyrtec fluoxetine cheap adipex buy ambien online losec ultram resocyanine generic lexapro cheap tramadol online buy nexium ciprofloxacin order vicodin online desyrel buy xanax buy valium levaquin buy prozac darvon buy soma online order ultram meridia online buy adipex online celecoxib presented nultianode fexofenadine diflucan autnorization nexium online buy ambien generic finasteride electropointing
hygrophobia generic zyrtec tramadol fosamax
airpark poplar aorta suffusion undignified semidecussation
Related Articles |
Metrics
Table of Content
