Inflorescence Initiation in Lolium Temulentum L.  XIII. the Role of Gibberellins

Evans, Lisa

doi:10.1071/bi9690773

Cited by 25 publications

(35 citation statements)

References 18 publications

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“…Gibbereilin A1 was relatively inactive in floral induction asjudged by both the length and the development stage of the shoot apex. It had been so in earlier experiments with Lolium, as were GA4, GA8, and GA9 also (4). A mixture of GA4 + GA7 was as effective as GA3 (5), implying that GA7 was effective for flowering, as is now found to be the case (Table IV).…”

Section: Resultssupporting

confidence: 56%

“…However, GA glucosyl conjugate-like substances are also present (Table I) and do change between SD (where less polar ones predominate; data not shown) and day II. There is an especially large peak (near the Rt ofGA,/GA3) which is bioactive in the immersion bioassay, but not in the microdrop bioassay, indicating that it may be a GA glucoside but is not a GA glucosyl ester or free GA (4,5), so leaf applications of GA3 in 10,l of 95% ethanol were compared with injections of aqueous solutions near the shoot apex. The results in Table III indicate that such leaf applications, although better suited for comparative studies because of their greater reproducibility, were rather less effective than injections near the shoot apex.…”

Section: Resultsmentioning

confidence: 99%

“…However, the growth retardant CCC did not prevent LD induction as it did in Samolus; in fact it substantially enhanced rather than reduced the effect of applied GA3 (4,5) and a comparable response has been found in another LDP, Blitum spp. (10).…”

mentioning

confidence: 95%

“…These were chosen to extend the results of earlier work with several GAs (4,5) in the light of changes in the endogenous GA-like substances found in the Lolium apex. Their structures are indicated in Figure 2.…”

mentioning

confidence: 99%

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Gibberellins, Endogenous and Applied, in Relation to Flower Induction in the Long-Day Plant Lolium temulentum

Pharis¹,

Evans²,

King³

et al. 1987

Plant Physiol.

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Changes in endogenous gibberellin-like substances (GAs) and related compounds in the shoot apices of Lolium temukntum during and after flower induction by one long day was examined for plants grown in three consecutive years. The total GA level in the shoot apical tissue was high (up to 42 mirograms per gram dry weight, or 3 x 10' molar GA3 equivalents) increasing several-fold on the day after the long day and then declning. Of the many GA-like substances present, the putative polyhydroxylated components-with HPLC retention times between those ofGAs (three hydroxyls) and GA32 (four hydroxyls), and accounting for about a quarter of the total GA activity-were most consistent and striking in their changes. Their level in the apices increased 3-to 5-fold on the day after the long day and then subsided. When varous GAs were applied to plants in noninductive short days, flower initiation was induced by several, most notably by GA32, GAs, 2,2-dimethyl GA4, GA3, and GA7. GA32 was most like one long day in eliciting a strong flowering response while having little effect on stem growth, whereas GA, had the opposite effect. It is suggested that highiy hydroxylated C-19 GAs may play a central role in the induction of flowering in this long-day plant. action (30).Many different endogenous GAs are found in plants, and changes in their concentration in shoot tissue occur following vernalization or photoperiodic induction, e.g. in spinach (28) and Agrostemma (11). Metzger and Zeevaart (18) have proposed that the conversion of GA,9 to GA20 in spinach is under photoperiodic control and conclude that the increase in GA20 is the cause of bolting in spinach, whereas in Agrostemma all the endogenous GAs underwent a transient increase following transfer to LD, associated with stem elongation (11).In the LDP Lolium temulentum, applications of GA3 and several other gibberellins induced flowering under noninductive SD. However, the growth retardant CCC did not prevent LD induction as it did in Samolus; in fact it substantially enhanced rather than reduced the effect of applied GA3 (4, 5) and a comparable response has been found in another LDP, Blitum spp. (10).In this paper, we present evidence for some of the changes in the endogenous GAs of L. temulentum during photoperiodic induction by a single LD, emphasizing the highly polar GAs in the true shoot apex, for which few data are available. These findings have led us to examine the effects of applications of several GAs, notably GA32, the results of which indicate very different specificities for stem growth on the one hand and for flower initiation on the other.Several kinds of evidence implicate the GAs2 in the initiation of flowering in photoperiodically sensitive plants. Applications of GA3 and other GAs replace the requirement for LD or low temperature vernalization in many species (22,29). With the LDP Samolusparviflorus, inhibitors ofGA synthesis can prevent flower initiation, this inhibition being reversed by application of GA3 (l). Applied GAs also replace the need for ...

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Section: Resultssupporting

confidence: 56%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 95%

mentioning

confidence: 99%

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Gibberellins, Endogenous and Applied, in Relation to Flower Induction in the Long-Day Plant Lolium temulentum

Pharis¹,

Evans²,

King³

et al. 1987

Plant Physiol.

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“…The second explanation (b above) involving substitution between phytochromes A and B (Table 11) requires two reasonable assumptions: that total Pfr is critical irrespective of its genetic origin and that, unlike hypocotyl growth, flowering of an LDP is optimal with low Pfr settings (see earlier discussion and Evans et al, 1965;Lane et al, 1965). Thus, despite its instability in light, there might have been sufficient phytochrome A in 8-h short days to allow it to contribute an EOD R/FR response in mutants lacking phytochrome B (Table 111, whereas phytochrome B would operate normally in the phytochrome A mutant.…”

Section: Phytochrome Overexpression and Flowering Response To Differementioning

confidence: 99%

Flowering Responses to Altered Expression of Phytochrome in Mutants and Transgenic Lines of Arabidopsis thaliana (L.) Heynh

et al. 1995

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l h e long-day plant Arabidopsis tbaliana (L.) Heynh. flowers early in response to brief end-of-day (EOD) exposures to far-red light (FR) following a fluorescent short day of 8 h. FR promotion of flowering was nullified by subsequent brief red light (R) EOD exposure, indicating phytochrome involvement. The EOD response to R or FR is a robust measure of phytochrome action. Along with their wild-type (WT) parents, mutants deficient in either phytochrome A or B responded similarly to the EOD treatments. Thus, neither phytochrome A nor B exclusively regulated flowering, although phytochrome B controlled hypocotyl elongation. Perhaps a third phytochrome species is important for the EOD responses of the mutants and/or their flowering is regulated by the amount of the FR-absorbing form of phytochrome, irrespective of the phytochrome species. Overexpression of phytochrome A or phytochrome B resulted in differing photoperiod and EOD responses among the genotypes. The day-neutra1 overexpressor of phytochrome A had an EOD response similar to all of the mutants and WTs, whereas R EOD exposure promoted flowering i n the overexpressor of phytochrome B and FR EOD exposure inhibited this promotion. The comparisons between relative flowering times and leaf numbers at flowering of the overexpressors and their WTs were not consistent across photoperiods and light treatments, although both phytochromes A and B contributed to regulating flowering of the transgenic plants.

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Hormonal Regulation of Flowering

Tanimoto¹,

Harada²

1985

Hormonal Regulation of Plant Growth and Development

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Inflorescence Initiation in Lolium Temulentum L. XIII. the Role of Gibberellins

Cited by 25 publications

References 18 publications

Gibberellins, Endogenous and Applied, in Relation to Flower Induction in the Long-Day Plant Lolium temulentum

Gibberellins, Endogenous and Applied, in Relation to Flower Induction in the Long-Day Plant Lolium temulentum

Flowering Responses to Altered Expression of Phytochrome in Mutants and Transgenic Lines of Arabidopsis thaliana (L.) Heynh

Hormonal Regulation of Flowering

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