The relationship between phytochrome-photoequilibrium and Development in light grown Chenopodium album L.

Morgan, D. C.; Smith, Harry

doi:10.1007/bf00388211

Cited by 159 publications

(105 citation statements)

References 18 publications

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“…2). This is consistent with the common observation that FRL administered at the end of, or as a supplement to the main photoperiod causes enhanced growth of both petioles and stems in a variety of other species (11,12,14,16,20). Spinach is a rosette plant with a LD requirement for the initiation of flowering and stem elongation (14,21).…”

Section: Methodssupporting

confidence: 91%

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Gibberellins and Light Regulated Petiole Growth in Thlaspi arvense L

Metzger¹

1988

Plant Physiol.

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Petiole growth in Thlaspi arvense L. was stimulated when a basic 8 hour photoperiod (4.20 milliwatts per square centimeter) was extended with low intensity light (0.16 milliwatt per square centimeter) from incandescent lamps. The day length extension was effective only when the light contained high proportions of far red light. Exogenous gibberellin A3 (GA3) could partially substitute for the promotive effect of the extended photoperiod. Moreover, the GA biosynthesis inhibitor 2-chlorocholine chloride inhibited the increase in petiole growth induced by the extended photoperiod. However, evidence was obtained indicating that gibberellins do not mediate the effect of the extended photoperiod. First, petiole growth was greater in plants receiving both exogenous GA3 and a day length extension than the sum of the effects of the two treatments alone. Second, petioles were sensitive to exogenous GA3 only during the early stages of leaf development, whereas mature (but not senescent) leaves continued to respond to an extension of the photoperiod. Third, the cellular basis for growth induced by extending the photoperiod was different from that observed with GA3. It was concluded that light and gibberellins are both important in the overall regulation of petiole growth, but act through independent mechanisms.Field pennycress (Thlaspi arvense L.) is a winter annual weed that has a cold requirement for stem elongation and flowering. Work in this laboratory has been focused on the role of GAs' in the environmental control of stem elongation in this species (8,9). During the course of these studies we observed that photoperiod exerts a strong influence on leaf growth, particularly petiole length. Petioles from plants that had been transferred to LD were longer than from plants maintained under SD. Furthermore, application of GA3 to plants in SD caused petioles to elongate, thereby mimicking the effect of LD. These observations suggest that GAs may mediate the observed LD-induced increase in petiole growth. Indeed, evidence for a role of GAs in this phenomenon in spinach has been published (21). Thus, in the present paper we report the results of experiments with two objectives in mind: first, to characterize more completely the role of light in the regulation of petiole growth in field pennycress; and second, to test the hypothesis that GAs mediate LD-induced petiole growth. pots filled with vermiculite. The pots were continuously subirrigated with one-quarter strength Hoagland solution (1). The plants were grown under SD conditions at 21°C until they were ready for use, approximately 6 weeks after germination. MATERIALS AND METHODSLight Treatments. SD treatments consisted of 8 h of light from fluorescent and incandescent lamps (4.20 mW cm-2) followed by 16 h of darkness. LD treatments were composed of the same basic 8 h photoperiod as SD followed by 16 h of low intensity illumination from incandescent lamps (0.16 mW cm-2).The spectral dependency of the LD response was investigated by subjecting plants to 16 h of low ...

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Section: Methodssupporting

confidence: 91%

“…ratio of Pr to Pfr) brought on by increasing duration of light with higher proportions of FRL. In nature this can occur from the selective attenuation of RL by leaf canopies and atmospheric conditions such as passing clouds or twilight (4,5,11,12).…”

Section: Methodsmentioning

confidence: 99%

Gibberellins and Light Regulated Petiole Growth in Thlaspi arvense L

Metzger¹

1988

Plant Physiol.

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“…Could the initiation of timing be a response to some critical ratio of Pfr:Pww? This is apparently true for stem elongation and has been suggested for photoperiodic timing (11,16,27). If so, the critical night should be strongly influenced by the light quality just before darkness (i.e., establishment of various phytochrome ratios by light), and there should be some balance of R and FR that would be detected as darkness at any brightness level, at least during the first part of the dark period before sensitivity to light increases as reported in this paper.…”

Section: Discussionmentioning

confidence: 69%

Twilight Effect: Initiating Dark Measurement in Photoperiodism of Xanthium

Salisbury

1981

Plant Physiol.

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Six experiments studied the effects of low levels of red and far-red light upon the initiation of measurement of the dark period in the photoperiodic induction of flowering in Xanthium stunarium L. (cocklebur), a short-day plant, and compared effects with those of comparable light treatments applied for 2 hours during the middle of a 16-hour inductive dark period. Red Ught, or red plus far-red, at levels that inhibit flowering when applied during the middle of the inductive dark period, either had no effect on the initiation of dark measurement (ie., were perceived as darkness), or they delayed the initiation of dark measurement by various times up to the full interval of exposure (2 hours). Far-red Ught alone had virtually no effect either at the bnning or in the middle of the dark period. These results confirm that time measurement in the photoperiodic response of short-day Xanthium plants is not simply the time required for metabolic dark conversion of phytochrome. Results also suggest that the pigment system

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“…[4][5][6]. Accordingly, low R:FR can induce shade-avoidance responses in plants grown without neighbors (7,8), and plants blinded to FR-enrichment in a dense canopy fail to respond to neighbors at an early stage of competition (9). Although some additional above-ground neighbor detection signals are known, e.g., blue light depletion (10,11) and volatile ethylene accumulation (11), none of these acts as early as a decrease in the reflected R:FR.…”

mentioning

confidence: 99%

Plant neighbor detection through touching leaf tips precedes phytochrome signals

Wit

Kegge

Evers

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

101

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Plants in dense vegetation compete for resources, including light, and optimize their growth based on neighbor detection cues. The best studied of such behaviors is the shade-avoidance syndrome that positions leaves in optimally lit zones of a vegetation. Although proximate vegetation is known to be sensed through a reduced ratio between red and far-red light, we show here through computational modeling and manipulative experiments that leaves of the rosette species Arabidopsis thaliana first need to move upward to generate sufficient light reflection potential for subsequent occurrence and perception of a reduced red to far-red ratio. This early hyponastic leaf growth response is not induced by known neighbor detection cues under both climate chamber and natural sunlight conditions, and we identify a unique way for plants to detect future competitors through touching of leaf tips. This signal occurs before light signals and appears to be the earliest means of above-ground plant-plant signaling in horizontally growing rosette plants.competition | phenotypic plasticity | thigmomorphogenesis | canopy development P lant growth in dense vegetations is dominated by a fierce battle over resources. In competition for light, small size inequalities can have major effects on light capture and thus competitive power (1-3). Therefore, it is essential for plants in dense stands to timely respond to neighbor detection cues and adjust growth to that of their competitors. Reduction of the red (R):far-red (FR) ratio, signaled through phytochromes and caused by horizontal FR reflection from neighboring plants, is seen as the earliest above-ground detection signal of neighbors. The R:FR is decreased even before true shading occurs through overlap of leaves, and induces shade-avoidance responses such as upward leaf movement (hyponasty) and stem elongation that secure light capture during subsequent plant competition (reviewed in refs. 4-6). Accordingly, low R:FR can induce shade-avoidance responses in plants grown without neighbors (7,8), and plants blinded to FR-enrichment in a dense canopy fail to respond to neighbors at an early stage of competition (9). Although some additional above-ground neighbor detection signals are known, e.g., blue light depletion (10, 11) and volatile ethylene accumulation (11), none of these acts as early as a decrease in the reflected R:FR.The paradigm of decreased R:FR as the earliest neighbor-detection signal in competition for light has been a breakthrough in mechanistic plant competition research. Interestingly, this paradigm is based on research on stem-forming forbs and trees (12-14), but has not been studied in plants that lack an appreciable height growth before competition in the vegetative life stage, e.g., rosette species such as Arabidopsis thaliana and many other species. Here we study early neighbor detection in dense stands of Arabidopsis. Hyponasty appears to be the earliest shade-avoidance response and occurs exclusively in leaves that touch neighboring leaf tips, before a physiologi...

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The relationship between phytochrome-photoequilibrium and Development in light grown Chenopodium album L.

Cited by 159 publications

References 18 publications

Gibberellins and Light Regulated Petiole Growth in Thlaspi arvense L

Gibberellins and Light Regulated Petiole Growth in Thlaspi arvense L

Twilight Effect: Initiating Dark Measurement in Photoperiodism of Xanthium

Plant neighbor detection through touching leaf tips precedes phytochrome signals

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