The study of staminate and hermaphrodite flowers on floral development and microspogenesis in Koelreuteria henryi Dummer (Sapindaceae)
Date Issued
2007
Date
2007
Author(s)
Lin, Chiou-Huey
DOI
zh-TW
Abstract
Koelreuteria henryi Dummer (Sapindaceae) is a deciduous tree and endemic to Taiwan. This species has been widely cultivated as side tree. The inflorescence is thyrse mixed rhipidium. The flower is polygamous-andromonoecious with staminate and hermaphrodite flowers on the same plant, fertile and steril pollen grains are produced respectively. In this study, with the aids of LM, TEM, SEM and histochemical observations, it is attempted to reveal (1) the floral initiation, flowers' sex differentiation and sex expression in the inflorescence; (2) the similarity and dissimilarity between pollen morphology, pollen viability and cytoplasmic content in staminate and hermaphrodite flowers; (3) the cellular and organellar transformations during the microsporogenesis; and (4) the anther wall configuration at anthesis.
The results show that thyrse primordium of K. henryi was emerged from the shoot apical meristem in middle August and subtended conspicuously by bracts, which possesses numerous pedicellate flowers. Five sepal primodia intiated from the floral primodium in a spiral order. Then five petal primordia arised simultaneously in a whorl arrangement, followed by eight stamen primodia arised and last by pistil primodium.
The anther wall development of K. henryi conforms to the basic type, consisting of four different tissues: epidermis, endothecium, 2~3 middle layer and tapetum The anthers in staminate flower of K. henryi are opened by longitudinal splits to release 2-celled pollen with the help of insects-pollinators. Although the pollen grains from hermaphrodite flowers have ca. 15.3 % viability when tested with FCR reaction, no pollen grain germinated in vitro. In constrast, those pollen grains from the staminate flowers have higher germination rate (76.8 %) tested in vitro. The results of histochemical staining show that there is a remarkable difference in storage compounds between sterile and fertile pollen grains. In the former, lipids globules with fewer starch grains are detected in the cytoplasm, while in the latter, only lipid globules are detectable.
Cytokinesis in microspore mother cells is simultaneous, forming tetrahedral tetrads. The secretory tapetum has two organelles involved in production of lipid bodies were endoplasmic reticulum (ER) and elaioplast. During early-vacuolated stage, the tapetum has lipids in the endoplasmic reticulum. The elaioplasts of the tapetum produce numerous saturated and unsaturated lipids. At maturation stage, the plastoglobules released from elaioplasts coalesced with unsaturated lipids from endoplasmic reticulum to form the pollenkitt mass deposited on the exine.
At the time of pre-dehiscence, the epidermal and endothecium are still intact. Fibrous thickenings are formed in the cells of the endothecium. In staminate flowers, the septum separating anther locules was cleaved and the stomium was degenerated to release the pollen grains. In hermaphrodite flowers, all of these structures remained intact without any release of pollen grains. All two pollen grains possess a well-developed pollen wall (exine and intine). The exine is composed of tectum, columellae, foot layer and endexine. The intine (I) of aperture in fertile pollen grains was opened with conspicuous three strata. Sterile pollen grains display a thickness intine and exine in the aperture which was not opened.
According to this study, the flowers' sex differentiation in K. henryi are potentially developed as bisexual and only at the final stage (ovules formed) of development sex organs could be defined. Not only the staminate and hermaphrodite flowers have functionally and structurally difference, but also the fertile and steril pollen grains produced respectively.
Subjects
單性花
兩性花
小孢子發育
花部發育
Koelreuteria henryi
staminate
hermaphrodite
floral development
microsporogenesis
SDGs
Type
other
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-R91226001-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):494c411d6f94ad13677a52d31f901fb4