The temperatures of the roots, the apical meristem, and the shoots of Zea mays plants were varied independently of each other and the rates of leaf extension were measured. When the temperature of the apical meristem and region of cell expansion at the base of the leaf was kept at 25 °C, changes of leaf extension in response to changes of root and shoot temperatures were less pronounced. When the temperature of the meristematic region was changed by increments of 5 or 10 °C from 0 to 40 °C, and the root and shoot temperatures were kept at 25 °C, rapid changes in leaf extension occurred. It was concluded that the rates of leaf extension were controlled at root-zone temperatures of 5 to 35 °C by heating or cooling of the meristematic region. Changes in rates of leaf extension in response to changes in air temperature were attributed to direct effects on the temperature of the meristematic region and on the physiology of the leaf.

Leaf Extension in Zea mays

Studies on the translocation of foliar‐applied p32 and other radioisotopes in bean plants

Localized application of chemicals which inhibit metabolism, anoxia and low temperature have been used as tools in basic research to assess the role of energy metabolism in the various stages of the translocation process. The results of these studies are reviewed in this chapter. In addition to their theoretical implications, these studies of the relationship between energy metabolism and translocation have a number of direct practical applications. There are numerous studies relating altered energy metabolism to the rate and pattern of assimilate translocation in crop plant productivity (Nelson, 1963; Wardlaw, 1968; Loomis, Williams and Hall, 1971). Unfortunately the role of energy from metabolism in assimilate translocation in relation to crop productivity is not well understood. Another practical area supported by studies of metabolic inhibitors and translocation is that of the effect of atmospheric pollutants on translocation of assimilates. Little work has been done to investigate the effect of these agents on assimilate distribution resulting from metabolic inhibition. These and other potentially practical applications depend on a precise understanding of the effect of metabolic inhibitors on translocation.

Effects of Temperature, Anoxia and Other Metabolic Inhibitors on Translocation

15 Using inverse isotopic dilution techniques with.. I the uptake patterns of ammonium and nitrate of lettuce plants (Lac tuc a s ativa L e r; cult ivar 'Climax') were deter­ mined, under 8 9 13 5 18 ̂ and 23 ° C air temperatures and the combinations of those with 2°C for root environmental temperature. The absorption patterns for both ammonium and nitrate were linear functions of time for nutrient solu­ tions and air temperature. The absorption rates for ammonium and nitrate were promoted by increasing one or both air and root environ­ mental temperatures. Nitrate uptake was influenced more by temperature than the absorption of ammonium. The ammonium to nitrate ratio increased when the temperature decreased. A higher temperature coefficient for nitrate was obtained. The translocation rates to tops for ammonium increased as temperature increased from 8 to 230 C. How­ ever ̂ for nitrate the translocation rates reached a maximum at l8°C.

/pdf/temperature-influence-on-ammonium-and-nitrate-absorption-by-4378o0k7l8.pdf

Temperature influence on ammonium and nitrate absorption by lettuce

A. Einleitung Die noeh immer vSllig rgtselhafte Frage nach der Mechanik des Stofftransports in den Siebr6hren bietet zur Zeit zwei grol]e Aspekte, unter denen eine LSsung des Problems versueht werden kann. Auf der einen Seite stehen die Anhgnger eines durch die SiebrShren flutenden Massenstroms, wie er zum ersten Male in der geistreiehen Theorie yon M/3~c~ (1930) postuliert worden ist. Die Einfaehheit dieser Hypothese, die zugleieh ihre Sts wie ihre Schw~che bedeutet, wird heute ~eilweise durch den Versueh abgesehwgeht, den Geleitzellen einige vitale Funktionen beim Stofftransport zu~uweisen, so etwa eine rege Phosphataset/itigkeit beim Stoffeinund -austritt (WANNE~ 1952, BAUE~ 1953, ZIEGLE~ 1956), w//hrend die kernlosen SiebrShren selbst noeh immer als inaktive R5hren betrachtet werden, in denen eine LSsung yon Nahrungsstoffen strSmt, wobei die Sehwierigkeiten der Siebplattenhindernisse und ihres Callusbelages z.T. durch einen angeblieh ,,prgmortalen\" Zustand des SiebrShrenprotoplasten umgangen werden sollen (I-Iu~EI~ 1941, CRAFTS 1951). Das SiebrShrenprotoplasma soll kaum mehr einen eigenen Stoffwechsel besitzen, Fermente werden ihm, da im SiebrShrenzellsaft (,,SiebrShrensaft\") bisher nieht aufzufinden (WANN~ 1953, ZI~GLE~ 1956), abgesprochen, und gewisse Vorstellungen vom Fehlen des Tonoplasten und eines kontinuierlichen ~berganges zwischen Plasma und Zellsaft in den Siebr6hren vollenden endlieh das Bild. Auf der anderen Seite stehen die Autoren, die einen Massenstrom, d.h. den gleiehzeitigen Transport aller in den Siebr6hren anwesenden Stoffe dureh Bewegung des L6sungsmittels nieht ffir erwiesen, ja ffir unwahrscheinlich halten, sondern einer aktiven Ts des Siebr5hrenplasmas und evtl. der Geleitzellen und einer unabhiingigen Wanderung der einzelnen Stoffe ohne LSsungsmittel zuneigen, wobei einem gelegentliehen Transport auch yon Wasser keine grunds~tzlichen Schwierigkeiten entgegenstehen (Mason und Mitarbeiter 1936, Sc~uMACE]~R u.a.) . Sie betrachten den Stofftransport als ein iiberaus

Über die Hemmung des Stofftransports in den Siebröhren durch lokale Inaktivierung verschiedener Atmungsenzyme

hydrate materials through petioles, will be influenced by temperature effects on numerous other processes occurring in various parts of the plant, such as respiration and assimilation, and the effect these processes have on concentration gradients between regions of export and import. Studies, therefore, in which the entire plant is subjected to different temperatures (4), although contributing much data of value, do not permit a clear analysis of the temperature effect on the process of translocation per se. In the present experiments, therefore, only the petiole temperature was varied, the rest of the plant in all treatments being maintained at a temperature of 20 ? Io C. Materials and methods The report by Weintraub and Brown (?) that stem elongation of ??aseolus vulgaris var. Black Valentine was directly proportional, within the range of 0 to .75 M, to the concentration of sugar supplied to the leaves suggested that this relationship could be used as a basis of approach for studying the effect of temperature on translocation of carbohydrates. If temperature has an effect on the rate of movement of sugar through the petiole then the amount of sugar reaching the growing tip will vary with temperature and the rate of elongation should vary accordingly. Stem elongation may then be used as an index to the effect of temperature on translocation of sugar. The basic features of the method, therefore, consisted of jacketing the petiole of one primary leaf, immersing the blade in sugar solution and measuring the subsequent elongation of the plant occurring in the dark. Seeds of Phaseolus vulgaris, variety Burpee's Stringless Greenpod (in

The effect of petiole temperature on the translocation of carbohydrates from bean leaves

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The effect of petiole temperature on the translocation of carbohydrates from bean leaves