Winter-annual ecotypes of Arabidopsis are relatively late flowering, unless the flowering of these ecotypes is promoted by exposure to cold (vernalization). This vernalization-suppressible, late-flowering phenotype results from the presence of dominant, late-flowering alleles at two loci, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). In this study, we report that flc null mutations result in early flowering, demonstrating that the role of active FLC alleles is to repress flowering. FLC was isolated by positional cloning and found to encode a novel MADS domain protein. The levels of FLC mRNA are regulated positively by FRI and negatively by LUMINIDEPENDENS. FLC is also negatively regulated by vernalization. Overexpression of FLC from a heterologous promoter is sufficient to delay flowering in the absence of an active FRI allele. We propose that the level of FLC activity acts through a rheostat-like mechanism to control flowering time in Arabidopsis and that modulation of FLC expression is a component of the vernalization response.

/pdf/flowering-locus-c-encodes-a-novel-mads-domain-protein-that-2sh6rjg4ct.pdf

FLOWERING LOCUS C Encodes a Novel MADS Domain Protein That Acts as a Repressor of Flowering

Taxomyces andreanae, a fungal endophyte, was isolated from the phloem (inner bark) of the Pacific yew, Taxus brevifolia. The fungus is hyphomyceteous and, when grown in a semi-synthetic liquid medium, produced taxol and related compounds. Taxol was identified by mass spectrometry, chromatography, and reactivity with monoclonal antibodies specific for taxol. Both [1-14C]acetic acid and L-[U-14C]phenylalanine served as precursors of [14C]taxol in fungal cultures. No taxol was detected in zero-time cultures or in the small agar plugs used to inoculate the culture flasks.

https://science.sciencemag.org/content/sci/260/5105/214.full.pdf

Taxol and Taxane Production by Taxomyces andreanae, an Endophytic Fungus of Pacific Yew

The term phenology is derived from the Greek word phaino meaning to show or to appear. Hence, phenology is defined as the study of the seasonal timing of life cycle events. For plants the seasonal timing of such events can be critical to survival and reproduction. In agriculture the most common failure of introduced crops is the inability to adjust to the seasons imposed by the new, environment (68). In the past few years, interest in the ecology and evolution of timing of life cycle events has grown. Here we review the literature on phenological patterns of germination, flowering, and fruiting (including dispersal).

/pdf/phenological-patterns-of-terrestrial-plants-2339nfk6dp.pdf

Phenological Patterns of Terrestrial Plants

A substantial literature is reviewed which indicates that compensatory growth upon tissue damage by herbivory is a major component of plant adaptation to herbivores. Experiments in Tanzania's Serengeti National Park showed that net above-ground primary productivity of grasslands was strongly regulated by grazing intensity in wet-season concentration areas of the large ungulate fauna. Moderate grazing stimulated productivity up to twice the levels in ungrazed control plots, depending upon soil moisture availability. Productivity was maintained at control values even under very intense grazing, suggesting that conventional definitions of overgrazing may be inapplicable to these native plant-herbivore systems. A laboratory clipping experiment with a sedge abundant in one of the most intensely utilized regions resulted in a maximum net above-ground productivity of 11.6 g/m2 · day when clipped daily at a height of 4 cm. Few plant species have been reported with the ability to maintain a significant level of pr...

Grazing as an Optimization Process: Grass-Ungulate Relationships in the Serengeti

Plants respond to the changing seasons to initiate developmental programmes precisely at particular times of year. Flowering is the best characterized of these seasonal responses, and in temperate climates it often occurs in spring. Genetic approaches in Arabidopsis thaliana have shown how the underlying responses to changes in day length (photoperiod) or winter temperature (vernalization) are conferred and how these converge to create a robust seasonal response. Recent advances in plant genome analysis have demonstrated the diversity in these regulatory systems in many plant species, including several crops and perennials, such as poplar trees. Here, we report progress in defining the diverse genetic mechanisms that enable plants to recognize winter, spring and autumn to initiate flower development.

The genetic basis of flowering responses to seasonal cues

https://science.sciencemag.org/content/sci/125/3249/650.2.full.pdf

Effect of Kinetin on Protein Content and Survival of Detached Xanthium Leaves

Flower initiation marks the transition from vegetative to reproductive growth in seed plants. It is thus a crucial event in the life of these plants, particularly so because of the peculiar relation of vegetative and reproductive development in seed plants which is in turn an outcome of the morphological nature of the flower. Flowers are modified shoots which are produced by modified shoot meristems, the flower primordia. However, once a meristem has been determined as a flower primordium, it is usually unable — except perhaps at the very earliest stages — of reverting to vegetative growth. Vegetative growth and reproductive development in seed plants are thus in a certain sense mutually exclusive; as far as a particular meristem is concerned, flower initiation means the end of its life. The central problem of the physiology of flower initiation is to understand which factors cause a shoot meristem to become a flower primordium, and how they consummate their action.

Physiology of flower initiation

Physiology of Flowering

The physiology of flowering.

The last comprehensive review on gibberellins in this series was by Paleg (1) and covered the literature through most of 1964. Since that time, research in the field has been very vigorous and cannot be covered in a single review, at least not if it is to be done critically, providing some analysis of the sub­ ject. This review, therefore, looks at the GAs themselves: their chemical structure, their biogenesis, transport, conversions, and a few related prob­ lems such as the so-called bound GAs. Gibberellins as regulators of plant growth and development will have to be the subject of some later review. A comprehensive survey of the chemistry and physiology of the GAs has been recently published by Tamura et al. (2), although its value for some readers may be impaired by the fact that it is written in Japanese. A transla­ tion should be seriously considered. Schneider et al. (3) have compiled a tabular survey of all GAs, their derivatives, and degradation products known by 1965. A brief, good review, which in times of coverage does not go much beyond Paleg's ( 1 ) , however, has been written by Brian (4); a review of GA biosynthesis has been published by Cross (5) . The relations between the action of GA (as well as other phytohormones) and nucleic acid and protein metabolism have recently been discussed by Key (6).

Anton Lang

Papers

Effect of Kinetin on Protein Content and Survival of Detached Xanthium Leaves

Physiology of flower initiation

Physiology of Flowering

The physiology of flowering.

Gibberellins: Structure and Metabolism