Page 6 - Morphoanatomical investigations of cones and pollen in Cathaya argyrophylla Chung & Kuang (Pinaceae, Coniferales) under systematical and evolutional aspects

V. M. Dörken and H. Nimsch Feddes Repertorium 2014, 125, 25–38

which do not undergo further growth after anthesis. In rangium opens along a longitudinal preformed line
ripe cones only the seed-scales are visible from outside (Fig. 5). The microsporangia start releasing the pollen
(Fig. 1E). when the cone is not already opened and the cone axis
Each seed-scale develops two ovules on its upper has not reached its final length. The pollen is released
surface, with the micropyle towards the cone axis over a period of 7–10 days. Only a small part of the
(Fig. 2A, D). The seed-scale and the ovules develop pollen is taken out directly out from the microsporangia
nearly simultaneous (Fig. 3A). The integument encloses by airflow. The majority of released pollen accumulates
the nucellus secondarily (Fig. 3B). By elongation of the first on the upper surface of the proximal microsporan-
two opposite sides of the originally tubular micropyle two giophores especially on the surface of their phylloid
equally developed micropylar arms are developed. rests. From here the pollen gets secondary transported
These micropylar arms are inside sticky and capture the by the airflow.
windborne pollen. Pollination drops could not yet be The pollen grains are bisaccate (Fig. 6A, B). Its
observed. The micropyles are between 100–120 μm in overall length incl. the sacci varies between 40–50 μm.
diameter (Fig. 2F). In the middle of the seed-scale a The hemispheric sacci are between 17–20 μm in diam-
further bulge is developed between the two ovules, eter and between 16–18 μm in height. They are broadly
which is no more recognizable at maturity (Fig. 2D, E). attached to the corpus (Fig. 6B). The inner surface of the
Seed-cones ripe in the second year, 16–18 months sacci is alveolate (Fig. 6D). The exine of the sacci is
after pollination. Ripe seed-cones are 3–5 cm long and between 1.5–2 μm thick. The shape of the corpus is
1.5–2.5 cm in diameter (Fig. 1E). They are in a pendu- elliptic (majority) or rarely rhombic and between 30–
lous orientation. After releasing the seed, they remain for 33 μm × 23–26 μm long (Fig. 6C). The angle between
some years at the tree, before getting abscised as a the corpus and the attached two sacci varies between
whole. Mature seeds have a distinct wing. The seed 120°–140°. The outer surface of the sacci and the cor-
corpus is 6–7 mm long, 4–5 mm in wide and about 3 mm pus is perforated and microechinate with several spine-
thick. The seed wing is between 6–10 mm long and 4– like irregularly arranged mircostructures (Fig. 6F). Such
6 mm wide (Fig. 3F). spines are absent in the area of the leptoma. The sur-
face of the leptoma is verrucose (Fig. 6E).
3.2 Morphology and anatomy of pollen-cones
and pollen
4 Discussion
The pollen-cones develop solitary basal to the female
ones in the crown. They are inserted axillary at lateral 4.1 Comparisons to other Pinaceae
ascending branches of the previous year (Fig. 4A). Pol-
4.1.1 Seed-cones
len-cones develop from buds which are inserted in the
axil of a typical green needle-like trophophyll (Fig. 4B). Despite to the results of morpho-anatomical studies of
At the base of the pollen-cone several persisting vegetative and reproductive structures and embryologi-
bud-scales are inserted (Fig. 4A, B). At maturity pollen- cal and molecular studies the systematic position of
cones are 4.6–7.3 cm long and 1.3–1.7 cm thick Cathaya is still controversially. Some authors see a
(Fig. 4A). They are in an upright position (Fig. 4A). After close relationship between Cathaya, Larix and Pseu-
releasing the pollen they dry out soon and are later dotsuga (e.g. Frankis 1988, Farjon 1990; Wu & Hu
abscised as a whole. The pollen-cones consist of 97– 1997). Frankis (1988) described Cathaya as intermedi-
152 spirally set hyposporangiate sporangiophores ate between Larix and Pseudotsuga. Wu & Hu (1997)
(Fig. 4A). Bracts within the pollen-cone are always ab- suggest a close affinity to Pseudotsuga. Other authors,
sent. Each of the sporangiophores consists of a stalk however, see a close relationship between Cathaya,
(Fig. 4C, D), mostly two (Fig. 4E), rarely three (Fig. 4F) Picea and Pinus (e.g. Wang et al. 1998; Wang et al.
abaxial microsporangia and an adaxial green phylloid 2000; Hart 1987; Gernandt et al. 2008; Lin et al. 2010).
rest with a violet tip with a serrate margin. The tip of the Wang et al. (2000) and Gernandt et al. (2008) see Pinus
phylloid rest is orientated in an angle of nearly 70–80° to as sister to Picea and Cathaya. However Lin et al.
the stalk. The sporangia and the phylloid rest are (2010) & Hart (1987) have Picea sistered to Pinus and
strongly fused to each other (Fig. 4D). Before anthesis Cathaya. Hu et al. (1976) and Hu & Wang (1984) de-
the phylloid rests of the sporangiophores are covering scribed the systematic position of Cathaya as placed
the microsporangia of the more distal microsporangio- between Pinus, Picea and Pseudotsuga.
phores, so that in young pollen-cones nearly only the The results about the cone morphology of Cathaya
phylloid part is visible from outside. At anthesis the cone gained in this present study allow the allocation to both
axis elongates strongly so that the microsporangia are the Picea-Pinus complex and also to the Larix-
freely exposed to the airflow. At maturity each microspo- Pseudotsuga complex. However, apart from several

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