Vegetative Phenology and Growth of a Facultatively Deciduous Bamboo in a Monsoonal Climate1

Canopy closure, leaf flush, and ramet recruitment in Bambusa arnhemica, a semelparous, clumping bamboo from the Australian monsoonal tropics, were monitored monthly for 2.5 years at three sites along a flood gradient. Bambusa arnhemica was facultatively deciduous, remaining evergreen at a downslope riparian site but suffering total loss of canopy on a hillside for up to 4 mo during the dry season. Leaf flush was flexible, occurring after as little as 25 mm of rain at the onset of wet season, in response to unusual dry season storms, and apparently also in response to fire independent of rainfall. New culms emerged soon after leaf flush early in the wet season. Culm growth took place during the middle and late wet season, with peak elongation rates of 15–30 cm/day. Some growth continued into the dry season, mostly on branches and leaves of new culms at riparian sites. Not all culms completed elongation before the onset of the dry season, and those that did not were permanently stunted. The demands of culm elongation may limit the occurrence of bamboo in wet‐dry climates to areas with predictable and sustained wet season rainfall, but the flexibility of branching and leaf processes facilitates coping with, and permits exploitation of less predictable pre‐ and postmonsoonal rains. The bamboo growth form and phenological patterns differ markedly from those of dicotyledonous trees and shrubs.     

What is happening to the monocotyledons?

An attempt is made to elucidate some of the more pronounced departures from traditional classifications in the book The families of the monocotyledons byDahlgren and collaborators, which embodies the latest opinions of the lateRolf Dahlgren on the subject. Consideration is given to the treatment of theLiliiflorae (especiallyLiliales andAsparagales) andBromeliiflorae, and to the theory offered for the origin of the monocots which identifies theDioscoreales as the most primitive order of the subclass.Dahlgren aimed at an eclectic classification (one based on a combination of similarity criteria and phylogenetic criteria) and the results of his use of cladistic methods (in association withF. N. Rasumssen) to supply the phylogenetic input are assessed. The resulting system itself is considered in the light of the distinction drawn byJ. S. L. Gilmour between natural and artificial classifications and their respective uses.Dedicated to the memory of JohnS. L. Gilmour.     

The conserved nature and taxonomic utility of pollen morphology in Cantua (Polemoniaceae)

Pollen exine morphology of nine of the ten species of Cantua (Polemoniaceae) is examined using light and scanning electron microscopy. A total of 28 specimens of C. bicolor, C. buxifolia, C. candelilla, C. cuzcoensis, C. flexuosa, C. pyrifolia, C. quercifolia, C. volcanica, and an as yet undescribed species (Cantua sp. nov.) are examined using either fresh or herbarium material. Pollen grains are found to be spheroidal, pantoporate, and quite large; mean diameter varies from 62 to 87?μm. Mean number of pores varies from 4.5 to 21.2 and mean pore size varies from 4.86 to 12.40?μm. Pollen grains of all species have insulate semitectate sexines. This feature distinguishes the pollen of Cantua species from the remainder of the Polemoniaceae. Insulae are evenly distributed over the surface of the pollen grain, with the exception of C. flexuosa and occasionally C. buxifolia, where insulae are more sparsely and haphazardly distributed. The majority of the species examined have irregularly shaped tectal insulae, with the exception of the large rounded insulae in C. quercifolia and the elongated narrow insulae in C. volcanica. Cantua quercifolia and C. volcanica have supratectal verrucae, a possible synapomorphy. In comparison to close relatives, the pollen grains of Cantua are evolutionarily conserved, and show little variation among species.     

Recircumscription of the monocotyledonous family Petrosaviaceae to include Japonolirion

Most systematists have favored placing Petrosaviaceae close to the Triuridaceae (formerly positioned within Alismatidae) by focusing on the mycoheterotrophic habit and nearly free carpels of Petrosaviaceae. Others have favored a position near the melanthioid lilies, perhaps serving as a linking-family to the Triuridaceae. We discuss the results of recently published, independent, and combined DNA sequence analyses that indicate a strongly supported sister relationship betweenPetrosavia (Petrosaviaceae) andJaponolirion (Japonoliriaceae). Molecular data show no connection of these genera to the Alismatales (including Tofieldiaceae), the Melanthiaceae s. str., the Liliales, or the Triuridaceae (now in Pandanales), although there are morphological similarities to each of these groups. A relationship to the Pandanales has been indicated in some molecular analyses, but this is not supported by bootstrap/jackknife analyses or by most morphological characters. BothPetrosavia andJaponolirion are native to high-evelation habitats and have bracteate racemes, pedicellate flowers, six persistent tepals, septal nectaries, three nearly distinct carpels, simultaneous microsporogenesis, monosulcate pollen, and follicular fruits. Outside of the Alismatales, no other monocotyledons share this combination of features. We therefore suggest that the Petrosaviaceae be re-circumscribed to includeJaponolirion. If the family's isolated position among the monocot orders continues to be found in phylogenetic studies, then recognition of the already published order Petrosaviales would be appropriate.     

The anatomy and chemistry of the colour bands of grasstree stems (Xanthorrhoea preissii) used for plant age and fire history determination

A new method of ageing and determining the fire history of grasstrees, based on colour bands running along the stem, has been developed. As part of our evaluation of the technique, we examined the structural and chemical basis of the colour differences. Exposed ends of the leaf bases are cream, brown and black, with the inner cortex, especially in the black leaf bases, being darker than the outer cortex. There was no structural difference between the three leaf base types. Tannin concentration increased from cream to brown to black leaf bases, and from the inner to outer cortex, and remained quite stable over many years. Both water-soluble and insoluble pigments contribute to the darkness of the black leaf bases. A hydrophobic naphthoquinone was present in the conducting tissues of the vascular bundles, and related naphthalene-derivatives were present in the surrounding tissues. We conclude that the colour differences between the leaf bases have a chemical basis that can be linked to environmental changes: tannin cells to phenological effects, and naphthalene-derivatives in the vascular core to the passage of fire.     

IGT基因家族调控作物株型研究进展

紧凑株型与深根系结构是现代作物实现机械化种植和密植高产的理想株型形态,也是改良农作物遗传性状的目标之一。IGT基因家族参与作物株型的调节,主要由DRO1（DEEPER ROOTING 1）、TAC1（TILLER ANGLE CONTROL 1）和LA1（LAZY 1）三个亚族组成,通过植物激素和相关蛋白的调控参与作物形态构建。以单子叶作物水稻、玉米以及双子叶模式植物拟南芥和作物油菜为代表,综述了IGT基因家族成员在调控单双子叶作物形态中的进展,特别是在分枝（蘖）角度和侧根向重力性中的相关机制及异同,以期为深入研究作物形态构建的调控机制和培育高产、耐密植以及适应机械化收获理想株型作物提供理论参考。     

Single-step transformation for generating marker-free transgenic rice using the ipt-type MAT vector system

The ipt-type MAT vector uses the ipt gene for regeneration of marker-free transgenic plants. However, it was pointed out that this system was not suitable for most economically important crops that regenerated through auxin-dependent embryogenesis. We report a single-step transformation system of rice using MAT vector. When we transformed scutellum tissues of 5 days pre-cultured rice seeds, marker-free transgenic rice plants directly regenerated from 25.5% infected scutellum tissues without forming ipt-intermediates within 4 weeks after an infection. Excision of the ipt gene caused the regeneration of marker-free transgenic rice plants through embryogenic tissues. Therefore, this system needs no selective agent and no sexual crossing for identification of transgenic plants not containing a selectable marker gene. This system is highly effective for generation of marker-free transgenic plants in economically important crops.     

Saponin Glycosylation in Cereals

Triterpene saponins are glycosylated plant secondary metabolites that are common in dicotyledonous species but rare in monocots. These compounds are antimicrobial and are important for plant defence. They also have a variety of pharmaceutical and industrial applications. Oat (Avena spp.) produces triterpene saponins called avenacins, specialised metabolites that are not represented in other cereals. The avenacins are synthesised and stored in roots and provide protection against soil-borne fungal pathogens. Glycosylation is often critical for bioactivity of saponins. We are using a combination of mutant analysis, database mining, expression profiling and functional characterisation to identify glycosyltransferases required for addition of sugar units to avenacins. By identifying the molecular machinery required for avenacin biosynthesis we hope to understand the broader elements of the evolution of specialised metabolic pathways.     

单子叶植物叶片气孔观察方法改良的研究

通过对传统的植物叶片气孔观察方法的改良,建立了一种观察单子叶植物气孔的有效方法。该方法不仅能够分清上下表皮、准确定位,而且简单易行,具有很高的可靠性和稳定性。实验中采用该法可以准确地获得植物叶片的气孔参数,为植物学及生态学的相关研究提供方法上的参考依据。     

Fructose oligosaccharides in monocotyledons: A possible delimitation of the order liliales

Stems from 198 species representing 165 genera of 46 monocotyledonous families were examined for the presence of fructose oligosaccharides. Aside from occurring in the subfamily Festucoideae of the Poaceae, in Cyperaceae and in Zostera marina of the Zosteraceae, the sugars were found exclusively in some closely related liliaceous families. These are the Agavaceae, Alstromeriaceae, Amaryllidaceae, Cyanastraceae, Haemodoraceae, Iridaceae, Liliaceae, Ruscaceae and Xanthorrhoeaceae. On the other hand, the fructosides were not detected in representatives of certain families whose placement in the order Liliales is controversial or dubious. These are the Dioscoreaceae, Philesiaceae, Philydraceae, Pontederiaceae, Smilacaceae, Stemonaceae, Taccaceae and Velloziaceae. These findings support the assertion of some systematists that these latter families should perhaps not be placed in the order.