Planta
Planta 143, 309-313 (1978)
9 by Springer-Verlag 1978
Speetrophotometrie Phytochrome Measurements in Light-grown Arena sativa L. Merten Jabben I and Gerald F. Deitzer Smithsonian Institution, Radiation Biology Laboratory, 12441 Parklawn Drive, Rockville, MD 20852, USA
Abstract. Phytochrome was studied spectrophotomet-
rically in Arena sativa L. seedlings that had been grown for 6 d in continuous white fluorescent light from lamps. Greening was prevented through the use of the herbicide San 9789. When placed in the light, phytochrome (Ptot) decreased with first order kinetics (zl/2 ~ 2 h) but reached a stable low level (~2.5% of the dark level) after 36 h. This concentration of phytochrome remained constant in the light and during the initial hours of a subsequent dark period, but increased significantly after a prolonged dark period. Evidence suggests that the constant pool of phytochrome in the light is achieved through an equilibrium between synthesis of the red absorbing (Pr) and destruction of the far-red absorbing form (Pfr) of phytochrome. It is concluded that the phytochrome system in light-grown oat seedlings is qualitatively the same as that known from etiolated monocotyledonous seedlings, but different than that described for cauliflower florets. Key words:
Avena
-
Light-grown tissue -
Phyto-
chrome - San 9789.
Introduction
Since the first spectrophotometric detection of phytochrome in 1959, a great deal of information about this photoreceptor system has become available. However, investigations have been concerned primarily with the phytochrome system from dark-grown Present address: Biologisches Institut II, Universit~it Freiburg, SchfinzlestraBe 1, D-7800 Freiburg, Federal Republic of Germany Abbreviations." Pfr=the far-red light absorbing form of phytochrome; P~ =the red light absorbing form of phytochrome; Ptot: Pr--Pfr; ks : r a t e constant of P~ synthesis; ka =rate constant of Pfr destruction; MOPS=N-morpholino-3-propane-sulfonic acid; TRIS = Tris (hydroxymethyl) amino methane; San 9789 = 4-chloro5-(methyl amino)-2- (c~,e,~-trifluoro- m-tolyl)- 3(2H)-pyridazinone. San 9789 is sold commercially under the trade name Norflurazon and was obtained from Sandoz-Wander, Inc., P.O.B. 1489, Homestead, FI. USA.
seedlings because the fluorescence of chlorophyll makes spectrophotometric measurements of phytochrome in green plants impossible (Butler, 1962; Pratt, 1978). The only kinetic analysis of the phytochrome system in light-grown tissue has been carried out on the outer parts of cauliflower heads (Butler et al., 1963). These studies revealed that the phytochrome system was qualitatively different from that known from etiolated seedlings. The phytochrome pool was stable in the light and in the dark but, while darkreversion of Pfr t o Pr was normal, there was no evidence for Pfr destruction. However, there are indications that a generalisation to the phytochrome system in other light-grown plants cannot be made (Clarkson and Hillman, 1968). Due to the presence of chlorophyll this has not been tested rigorously. In a previous paper, we proposed a method for measuring phytochrome in light-grown plants (Jabben and Deitzer, 1978a). We used the herbicide San 9789 (Norflurazon), which effectively inhibits chlorophyll accumulation in white light, but leaves the phytochrome system unaffected (Jabben and Deitzer, 1978b). This suggests that the phytochrome system in these herbicide treated plants is essentially the same as the phytochrome system in green plants grown without the herbicide. In this publication we have examined the nonphotochemical reactions of the phytochrome system in these herbicide treated plants. We chose Arena, because its phytochrome system in etiolated seedlings is well known, it contains a relatively large amount of phytochrome, and is sensitive to the herbicide San 9789. The results suggest that the phytochrome system in light-grown oat seedlings is different from that found in cauliflower heads.
Materials and Methods Plant Material
Oat seedlings (Arena sativa L., cv. Garry; Asgrow Seed Company, Syracuse, N.Y., USA) were grown on one layer of moist Kimpack, containing 2 x 10- 4 M San 9789.
0032-0935/78/0143/0309/$01.00
310
M, Jabben and G.F. Deitzer: Spectrophotometric Phytochrome Measurements
cP r Garry
oat
1.0
T = 22~
Ptot /log FW
@ L) c o J~
600
L
650
.L
o .Q
II
,
Planta 143, 309-313 (1978)
9 by Springer-Verlag 1978
Speetrophotometrie Phytochrome Measurements in Light-grown Arena sativa L. Merten Jabben I and Gerald F. Deitzer Smithsonian Institution, Radiation Biology Laboratory, 12441 Parklawn Drive, Rockville, MD 20852, USA
Abstract. Phytochrome was studied spectrophotomet-
rically in Arena sativa L. seedlings that had been grown for 6 d in continuous white fluorescent light from lamps. Greening was prevented through the use of the herbicide San 9789. When placed in the light, phytochrome (Ptot) decreased with first order kinetics (zl/2 ~ 2 h) but reached a stable low level (~2.5% of the dark level) after 36 h. This concentration of phytochrome remained constant in the light and during the initial hours of a subsequent dark period, but increased significantly after a prolonged dark period. Evidence suggests that the constant pool of phytochrome in the light is achieved through an equilibrium between synthesis of the red absorbing (Pr) and destruction of the far-red absorbing form (Pfr) of phytochrome. It is concluded that the phytochrome system in light-grown oat seedlings is qualitatively the same as that known from etiolated monocotyledonous seedlings, but different than that described for cauliflower florets. Key words:
Avena
-
Light-grown tissue -
Phyto-
chrome - San 9789.
Introduction
Since the first spectrophotometric detection of phytochrome in 1959, a great deal of information about this photoreceptor system has become available. However, investigations have been concerned primarily with the phytochrome system from dark-grown Present address: Biologisches Institut II, Universit~it Freiburg, SchfinzlestraBe 1, D-7800 Freiburg, Federal Republic of Germany Abbreviations." Pfr=the far-red light absorbing form of phytochrome; P~ =the red light absorbing form of phytochrome; Ptot: Pr--Pfr; ks : r a t e constant of P~ synthesis; ka =rate constant of Pfr destruction; MOPS=N-morpholino-3-propane-sulfonic acid; TRIS = Tris (hydroxymethyl) amino methane; San 9789 = 4-chloro5-(methyl amino)-2- (c~,e,~-trifluoro- m-tolyl)- 3(2H)-pyridazinone. San 9789 is sold commercially under the trade name Norflurazon and was obtained from Sandoz-Wander, Inc., P.O.B. 1489, Homestead, FI. USA.
seedlings because the fluorescence of chlorophyll makes spectrophotometric measurements of phytochrome in green plants impossible (Butler, 1962; Pratt, 1978). The only kinetic analysis of the phytochrome system in light-grown tissue has been carried out on the outer parts of cauliflower heads (Butler et al., 1963). These studies revealed that the phytochrome system was qualitatively different from that known from etiolated seedlings. The phytochrome pool was stable in the light and in the dark but, while darkreversion of Pfr t o Pr was normal, there was no evidence for Pfr destruction. However, there are indications that a generalisation to the phytochrome system in other light-grown plants cannot be made (Clarkson and Hillman, 1968). Due to the presence of chlorophyll this has not been tested rigorously. In a previous paper, we proposed a method for measuring phytochrome in light-grown plants (Jabben and Deitzer, 1978a). We used the herbicide San 9789 (Norflurazon), which effectively inhibits chlorophyll accumulation in white light, but leaves the phytochrome system unaffected (Jabben and Deitzer, 1978b). This suggests that the phytochrome system in these herbicide treated plants is essentially the same as the phytochrome system in green plants grown without the herbicide. In this publication we have examined the nonphotochemical reactions of the phytochrome system in these herbicide treated plants. We chose Arena, because its phytochrome system in etiolated seedlings is well known, it contains a relatively large amount of phytochrome, and is sensitive to the herbicide San 9789. The results suggest that the phytochrome system in light-grown oat seedlings is different from that found in cauliflower heads.
Materials and Methods Plant Material
Oat seedlings (Arena sativa L., cv. Garry; Asgrow Seed Company, Syracuse, N.Y., USA) were grown on one layer of moist Kimpack, containing 2 x 10- 4 M San 9789.
0032-0935/78/0143/0309/$01.00
310
M, Jabben and G.F. Deitzer: Spectrophotometric Phytochrome Measurements
cP r Garry
oat
1.0
T = 22~
Ptot /log FW
@ L) c o J~
600
L
650
.L
o .Q
II
,
