Physiologia Plantarum

HEIDE, OLA M.

doi: 10.1111/j.1399-3054.1974.tb04983.xpmid: N/A

Growth and dormancy as affected by photoperiod and temperature have been studied in Norway spruce ecotypes of different latitudinal and altitudinal origin. First‐year seedlings were used. In all ecotypes apical growth cessation and terminal bud formation occurred within 2 weeks after exposure to SD at temperatures of 18 to 24°C. At lower temperatures or at near‐critical photoperiods the response was delayed. The critical photoperiod for apical growth cessation varied from 21 hours in ecotype Steinkjer, Norway (64°N) to about 15 hours in ecotype Lankowitz, Austria (47°04′N). High‐elevation ecotypes also had longer critical pholoperiods than low‐elevation ecotypes from the same latitude. A detectable growth depression resulted from as little as 1 or 2 SDs of 10 hours, and with 4 or more SDs apical growth cessation took place. In contrast to the situation in the shoot, root growth was not affected by photoperiod. Accordingly, the top:root ratio is drastically affected by photoperiod. The critical photoperiod for cambial growth was shorter than that for apical growth in all ecotypes and cambial growth cessation was delayed for several weeks compared with cessation of apical growth. A transition to formation of late‐wood tracheids with thick walls and narrow lumens took place upon exposure to SD. The photoperiodic effects were significantly modified by temperature, but the critical photoperiods were only slightly changed by temperature in the range of 12 to 24°C. However, a 10‐hour “night” at 4°C caused growth cessation in continuous light in four ecotypes tested. Temperature optimum for apical growth under non‐limiting photoperiods (24 hours) was 21°C in all ecotypes, but with little difference among 18,21 and 24°C. The Q10 for apical growth was 3.5 in the temperature range 12 to 18°C. The growth potential as determined in 24‐hour photoperiods was not significantly different among the various ecotypes except for one northern eco‐type which was clearly inferior to the others. However, the growth of ecotype Steinkjer (64°N) was greatly suppressed even by the long midsummer days at 59°40′N, thus demonstrating the misleading impression one gets of the growth potential of northern ecotypes when they are moved southwards.

WIDHOLM, J. M.

doi: 10.1111/j.1399-3054.1974.tb04984.xpmid: N/A

Shikimate, anthranilate, indole, l‐tryptophan, phenylpyruvate, l‐p henylalanine, p‐hydroxyphenylpyruvate or l‐tyrosine were added to suspension‐cultured Nicotiana tabacum (tabacco) and Daucus carota (carrot) tissues and incubated for 24 hours. Uptake of each compound was substantial as measured by its decrease in the medium. The levels of free tryptophan, phenylalanine and tyrosine were determined in the tissues after the 24 hours incubation. Shikimate did not change the aromatic animo acid levels in carrot tissue, but did increase all three in tobacco (3‐fold or more), indicating a less stringent feedback control in tobacco. Anthranilate and indole increased the tissue tryptophan levels in both species by at least 17‐fold, showing that the flow from anthranilate and indole to tryptophan was apparently unhindered by enzymatic control mechanisms. When tryptophan levels were elevated in both carrot and tobaccotissues by anthranilate, indole or tryptophan addition, there was also an increase in free phyenylalanine and tyrosine. This might be due to the reversal of phenylalanine and tyrosine feedback inhibition of chorismate mutase by the high tryptophan in the tissue. Chorismate mutase activity in tobacco crude extracts could be inhibited by 66–90% by 1 mM phenylalanine and /or tyrosine. Tryptophan at 1 mM stimulated the enzyme activity by 1/3 and completely reversed the phenylalanine and/or tyrosine inhibition of enzyme activity. Chorsimate mutase activity amino acids under a variety of conditions. Phenylpyruvate increased the phenylalanine levels and p‐hydroxyphenylpyruvate increased the tyrosine levels in carrot and tobacco tissues indicating that there was no feedback control of the last step in phenylalanine and tyrosine biosynthesis.

PARSONS, LAWRENCE R.; KRAMER, PAUL J.

doi: 10.1111/j.1399-3054.1974.tb04985.xpmid: N/A

The occurrence of diurnal changes in root resistance of cotton was studied by measuring the flow of water through 35‐to70‐day‐old root systems under a pressure of 3.10 bars or a vacuum of 0.88 bar. The volume of exudate obtained under constant pressure or constant vacuum was 2 to 3 times greater near midday than near midnight indicating that the root resistance apparently was 2 to 3 times greater at night than during the day. The salt concentration of the exudate also cycled; the concentration was lowest at midday and highest at night, hence there was little diurnal variation in the total amount of salt moved per hour. The cycle for volume of exduate, salt concentration, and apparent root resistance had a period of 22 to 26 hours at 24°C. The cycle gradually died away 2 to 3 days after removal of the shoots. The diurnal variations appeared to be controlled by signals from the shoots because the phase of the cycles could be reset by changing the light‐dark cycle under which the plants were grown. Cycling was eliminated by exposure to 8 or more days of continuous light before removing the shoots, and cycling could not be entrained by a 6 hour light‐6hour dark cycle. Bubbling nitrogen gas through the nutrient medium stopped cycling. A possible role of ion or growth regulator action is discussed.

IGHE, ULF; PETTERSSON, SUNE

doi: 10.1111/j.1399-3054.1974.tb04986.xpmid: N/A

Components of the initial uptake and active transport of rubidium were studied in potassium‐starved and potassium‐rich wheat plants. A metabolism‐linked component of the initial uptake in the root was identified by means of DNP‐treatment. It was shown that there is a direct proportionality between the magnitude of the metabolism‐linked component of the initial uptake and the rate of active uptake. It is suggested that, in the free space, this metabolism‐linked ion binding represents an initial step of the active ion transport preceding the subsequent carrier‐mediated transport across the plasmalemma.

ÖQUIST, GUNNAR

doi: 10.1111/j.1399-3054.1974.tb04987.xpmid: N/A

Phycocyanin‐free photosynthetic lamellae (PSI‐particles) were prepared from Anacystis nidulans, grown in complete and iron‐deficient media. French press treatment and fractionated centrifugation were used. Absorption studies of the particles revealed an iron deficiency‐induced shift of the main red chlorophyll a absorption peak from 679 to 673 nm as reported before for whole cells. The shift may reflect a changed distribution between different chlorophyll a forms. Action spectra for photo‐oxidation of mammalian cytochrome c with photosynthetic lamellae revealed an iron deficiency‐induced shift, corresponding to that found in the absorption spectra. As photo‐oxidation of cytochrome c is mediated by PSI, it is believed that chlorophyll a also after the shift towards shorter wavelengths, is active in PSI. A decreased photosynthetic capacity of PSI, due to iron deficiency, was shown by time course studies of photosynthetic oxygen evolution, by photo‐oxidation studies of P700 and mammalian cytochrome c, by photo‐reduction studies of NADP and by combined studies of light‐induced and chemical oxidation of P700. The ration chlorophyll a/700 was also determined for whole cells, lyophilized cells and PSI‐particles. Iron deficiency caused an increased ratio in all studied fractions. The results of this work imply that energy is transferred with less efficiency within the photosynthetic units of PSI in iron‐deficient A. nidulans than in iron‐supplied algae.

ÖQUIST, GUNNAR

doi: 10.1111/j.1399-3054.1974.tb04988.xpmid: N/A

Anacystis nidulans was grown in white light of two different intensities, 7 and 50 W ·m−2. The in vivo pigmentations of the two cultures were compared. The ratio phycocyanin/chlorophyll a was 0.96 for cells grown at 7 W · m−2 and 0.37 for cells grown at 50 W · m−2. Phycocyanin‐free photosynthetic lamellae (PSI‐particles) were prepared, using French press treatment and fractionated centrifugation. Algae grown in the irradiance of 50 W · m−2 showed a chlorophyll a/P700 ratio of 260, while algae grown at 7 W · m−2 had a value of 140. Corresponding PSI‐particles showed values of 122 and 109 respectively. Light‐induced absorption difference spectra measured between 400–450nm indicated different ratios between cytochrome f and P700 in the two algal cultures. Enhancement studies of photosynthetic oxygen evolution were carried out. When a background beam of 691 nm was superimposed upon a signal beam of 625 nm, good enhancement was observed for both cultures. With the wavelengths 675 and 691 nm together a pronounced enhancement could be detected only in algae grown at the higher light level. Absorption spectra recorded on whole cells at 77°K revealed a small shift of the main red chlorophyll a absorption peak caused by light intensity. It is proposed that the reduction of the phycocyanin/chlorophyll a ratio in high light‐grown cells is accompanied by an increased energy distribution by chlorophyll a into PSII.

ÖQUIST, GUNNAR

doi: 10.1111/j.1399-3054.1974.tb04989.xpmid: N/A

Anacystis nidulans was grown at two different levels of white light, 7 and50 W.m−2. The cells were disrupted through French press treatment, and phycocyanin‐free photosynthetic lamellae were obtained from the homogenate by fractionated centrifugation. Comparative absorption studies of the lamellae revealed that high intensity gave an increased carotenoid content relative to chlorophyll a. The spectral characteristics of the cell‐free supernatants were also analysed. The high light intensity gave increased contents of both pteridines (410 nm) and allophycocyanin (655 nm) compared with the contents in algae grown at the low light level.

WILLIAMS, M. W.; RAESE, J. T.

doi: 10.1111/j.1399-3054.1974.tb04990.xpmid: N/A

The influence of dormant‐season temperatures on levels of sorbitol was determined in an effort to provide further information on the possible role of sorbitol in dormancy of apple tress (Malus sylvestris Mill.). Two‐year‐old shoots were collected throughout the dormant season; sorbitol and sugars were determined in tracheal sap extracted under vacuum and in ground dried wood extracted in a soxhlet apparatus. Sorbitol and sugar trimethylsilyl derivatives were detected by gas chromatography. Levels of sorbitol in the sap generally increased during subfreezing temperatures and decreased during warm periods throughout the dormant season. Early peak increases in sap sorbitol appeared to coincide with the beginning of leaf senescence. Postharvest levels of reducing sugars, sorbitol, and particularly sucrose in the wood, increased as the temperature decreased during the dormant season, and the sugar levels decreased with warming temperatures in the spring. Our data indicate that sorbitol and sucrose are important reserves of storage carbohydrates in resting apple trees.

REID, D. M.; PHARIS, R. P.; ROBERTS, D. W. A.

doi: 10.1111/j.1399-3054.1974.tb04991.xpmid: N/A

Kharkov 22 M.C. winter wheat was grown continuously from seed under four temperature regimens; 2°C; 2°C then transferred to 20°C; 6°C, and 20°C. Plants were harvested at the 4‐leaf stage (except the 2°C plants which were harvested at the 3‐leaf stage) and the levels of endogenous gibberellins (GAs) were measured and their cold hardiness determined. The GA content of 20°C and the 6°C seedlings were about equal and greater (by 4‐ to 30‐fold) than the GA content of 2°C seedlings that had been transferred to 20°C (i.e. vernalized). The GA content of the 2°C seedlings was least of all, being 28‐ to 320‐fold less than the 20°C seedlings. At harvest the leaves of the 20°C seedlings were somewhat larger than those of the seedlings grown at 2°C and transferred to 20°C. The leaves of the 6°C seedlings were very much smaller and the leaves of the 2°C seedlings were smallest of all. It is concluded that while GAs may play a role in controlling leaf size and level of cold hardiness of wheat, they are not the most important factor.

KYLIN, ANDERS; OKKEH, ASSAD

doi: 10.1111/j.1399-3054.1974.tb04992.xpmid: N/A

Narrow concentration intervals were used, covering 10−6– 10−4M desaspidin. The interaction with glycolysis involves three steps, the inhibitor constants (Ki:s) being in turn 2.7 × 10−5M, 1.3 × 10−4M, and high. About 18% of total glycolysis is inhibited in each of the two first steps, and 65% left for the third reaction. After compensation for glycolysis, oxidative phosphorylation may show a sudden jump to about 10% inhibition at 1.5 × 10−5M desaspidin, the possible Ki of the reaction starting here being very high. Correcting for glycolysis, desaspidin affects total Photophosphorylation in two steps, with the Ki values of 7.8 × 10−5M and 4.6 × 10−4M respectively. Inhibition in the first step is about 27% of the total photophosphorylation. By applying 10−6M DCMU(/3‐(3, 4‐dichlorophenyl)‐l, l‐dimethy lurea), one can abolish non‐cyclic photophosphorylation. Desaspidin then reacts in a single step with a Ki of 1.4 × 10−4M. At 5 × 10−5M DCMU, also the pseudocyclic photophosphorylation is abolished. The remaining, true cyclic photophosphorylation has a single Ki of 2.3 × 10−5M for desaspidin. Under non‐cyclic conditions, the true cyclic process contributes about 25% to total Photophosphorylation. Under pseudocyclic conditions, no cyclic photophosphorylation occurs. Under true cyclic conditions, the non‐cyclic and pseudocyclic processes are inoperative. This indicates a regulative system, so that either (1) the (non‐cyclic + true cyclic), (2) only the pseudocyclic, or (3) only the true cyclic systems can be traced, dependent on the level of DCMU applied. There are two sites for non‐cyclic Photophosphorylation, one of them common to the pseudocyclic pathway. Cyclic photophosphorylation has a third site, different from the other two.