Cell Division Control in Plants

362 C.L.H.Hord·H.Ma

Table 1Stages ofArabidopsisanther development

Anther Major events and morphological markers Tissues
stagea present

1 Stamen is round with three major cell layers L1, L2, L3

2 Stamen becomes oval shaped; archesporial cells are in the

four corners of the L2 layer

Ep, Ar, L3

3 Archesporial cells have divided parallel to the epidermis

to form the primary parietal and primary sporogenous

cells in the lobes

Ep, PP, PSp,

L3

4 Primary parietal cells have divided parallel to the epi-

dermis to form the inner secondary parietal and outer

secondary parietal cell layers; they begin to form concen-

tric rings around the sporgenous cells. The Vascular and

connective become distinguishable

Ep, ISP, OSP,

Sp, V

5 One of the secondary parietal layers has divided peri-

clinally at the outer surface, three L2-derived cell layers

surround the pollen mother cells. At late stage five, cal-

lose begins to form around PMCs

Ep, En, ML, T,

PMC, C, V

6 A thick callose layer is apparent surround the pollen

mother cells, which enter and go through meiosis. The

middle layer becomes compressed and appears as a thin

line. Tapetum becomes vacuolated

Ep, En, ML, T,

Mc, PMC, V

7 Meiosis has completed with cytokinesis. Tetrads of mi-

crospores appear in the locules.

Ep, En, ML, T,

Td, C, V

8 Microspores are free within in the locules after the callose

wall is degenerated. Middle layer is no longer visible.

Ep, En, T,

MSp, C, V

9 Microspores generate an exine wall and become vacuo-

lated. Septum is visible using TEM

Ep, En, T,
Msp,
C, V, Sm
10 Tapetum degeneration is initiated Ep, En, T,
Msp, C, V, Sm
11 Microspores undergo three rounds of mitotic divisions.
Tapetum continues to degenerate. Endothecium and epi-
dermis appear highly vacuolated. Septum cells begin to
degenerate

Ep, En, T,

Msp, C, V,

Sm, St

12 Tricellular pollen grains are visible. Septum degeneration
and breakage cause the anthers to become bilocular. Dif-
ferentiated stonium visible using TEM.

Ep, En, PG, C,

V, S t

13 Breakage along stonium allows for pollen release-de-
hiscence

Ep, En, PG, C,
V, S t
14 The stamen senesces as the cells shrink Ep, En, C, V

aAnther stages were taken from Sanders et al. (1999).

Ar, archesporial cells; Ep, epidermis; PP, primary parietal cells; PSp, primary sporoge-
nous cells; ISP, inner secondary parietal cells; OSP, outer secondary parietal cells; Sp,
sporogenous cells; V, vascular tissue; En, endothecium; ML, middle layer; T, tape-
tum; PMC, pollen mother cells; C, connective tissue; Mc, meiocyte; Td, tetrads; Msp,
microspores; Sm, septum; St, stonium; PG, pollen grain