Physiological Signals That Induce Flowering.

Abstract

INTRODUCTIONThe timing of the transition from vegetative growth to flowering is of paramount importance in agriculture, horticulture, and plant breeding because flowering is the first step of sexual reproduction. Studies to understand how this transition is controlled have occupied countless physiologists during the past half century and have produced an almost unmanageably large amount of information (Bernier et al., 1981a; Halevy, 1985 Halevy, -1989Bernier, 1988;Kinet, 1993).A majority of plants use environmental cues to regulate the transition to flowering because all individuals of a species must flower synchronously for successful outcrossing and because all species must complete their sexual reproduction under favorable externa1 conditions. Any environmental variables exhibiting regular seasonal changes are potential factors that control the transition to flowering. The major factors are photoperiod, temperature, and water availability. Plants that do not require a particular photoperiod or temperature to flower, i.e., the so-called "autonomous-flowering" plants, are usually sensitive to irradiance. The environmental factors are perceived by different parts of the plant. Photoperiod and irradiance are perceived mainly by mature leaves in intact plants. Temperature is perceived by all plant parts, although low temperature (vernalization) is often perceived mainly by the shoot apex. Water availability is perceived by the root system.There are strong interactions between these different factors, so that each factor can change the threshold value for the effectiveness of the others. Plants, as opportunists, will thus make use of a different critical factor in different environments. Melilotus officinalis, for example, is a biennial with a vernalization requirement in temperate zones and an annual long-day (LD) plant with no cold requirement in arctic regions. In photoperiodic species, such as the short-day (SD) plant Pharbitis nil and the LD plant Silene armeria, flowering in unfavorable photoperiods can be caused by changing temperature, irradiance, or nutrition or by removing the roots. Similarly, in some late-flowering mutants of Arabidopsis, vernalization and an increase in the proportion of far-red light in the light source can substitute for one another in promoting the transition to flowering (Martínez-Zapater and Somerville, 1990; Bagnall, 1992). Clearly, there are alternate pathways to flowering in most, ifTo whom correspondence should be addressed. not all, plants. Because the different flowering-promoting factors are perceived by different parts of the plant, this implies that these parts interact and that the fate of the apical meristem-remaining vegetative or becoming reproductive-is controlled by an array of long-distance signals from the entire plant.The ability of subsets of plant parts to control flowering is also underscored by the fact that some plants may flower almost normally after complete defoliation (Hyoscyamus niger, red Perilla, Chenopodium amaranticolor) or derooting (Perilla, Loli...

Reproductive physiology of mango

“…vegetative shoot (vegetative induction), generative shoot (floral induction) or mixed shoot (combined vegetative-floral induction) in initiating shoots. This definition differs from that developed from herbaceous plant flowering models (Bernier et al, 1981(Bernier et al, , 1993Halevy, 1985Halevy, -1986Bernier, 1988;Huala and Sussex, 1993;Kinet, 1993). In those flowering models, a critical photoperiod or vernalization treatment or both, induces production of a floral stimulus.…”

Oxidative stress tolerance and longevity in Arabidopsis: the late‐flowering mutant gigantea is tolerant to paraquat

“…The transition to flowering is a complex process that is regulated by many factors (Bernier et al, 1993;Coupland, 1995;Martínez-Zapater et al, 1994). Because mutations that reduce growth rate can also cause a delay in flowering time, only mutants showing a correlative increase in leaf number are considered as late flowering sensu stricto (Koornneef et al, 1991).…”

Hexokinase as a sugar sensor in higher plants.

“…In higher plants, sugars affect growth and development throughout the life cycle, from germination to flowering to senescence (Steeves and Sussex, 1989;Brusslan and Tobin, 1992;Graham et al, 1992;Bernier et al, 1993;Sheen, 1994;Thomas and Rodriguez, 1994;Dangl et al, 1995). Recently, it has become apparent that sugars are physiological signals repressing or activating plant genes involved in many essential processes, including photosynthesis, glyoxylate metabolism, respiration, starch and sucrose synthesis and degradation, nitrogen metabolism, pathogen defense, wounding response, cell cycle regulation, pigmentation, and senescence (Chen et al, 1994;Knight and Gray, 1994;Lam et al, 1994;Sheen, 1994;Herbers et al, 1995;Mita et al, 1995;Reynolds and Smith, 1995).…”