THE VEGETATIVE DEVELOPMENT OF THE POTATO PLANT

A study of the vegetative growth of potato plants indicated that all varieties grown under identical conditions are likely to show similar growth rates during the early stages of development.
Differences in total leaf area per plant between varieties became apparent at the stage when rapid development of axillary shoots from the main axis occurred. The maincrop varieties, Stormont Dawn and King Edward, attained a greater total leaf area than the early varieties, Ulster Chieftain and Arran Pilot, because of the greater development of axillary shoots.
It is suggested that the number of nodes produced beneath the terminal inflorescence on the main axis approximates to a constant value, independent of variety. Varietal differences were manifested in the distribution between leaves above ground and stolons below, the early varieties producing fewer leaves above ground than the maincrop, in inverse proportion to the number of underground stolons.
The yields of tubers per plant are given for four varieties. Differences between varieties in the rate of tuber formation are related to differences in the development of haulms.
It is considered probable that the potato plant exhibits a basic growth form which is modified in each variety in a characteristic manner according to the stage in the growth cycle and the rate at which the growth substances are distributed to the various organs of the plant.     

THE ACTION OF THE PLANT GROWTH HORMONE

1. Sections of Avena coleoptiles are found to show a considerable elongation when suspended in solutions of growth substance. 2. This elongation does not take place in the absence of O₂ and is inhibited by KCN and phenylurethane. 3. The rate of respiration of sections of coleoptiles is increased by the addition of growth substance in concentrations which cause growth. High concentrations of growth substance inhibit growth and also respiration. 4. The increase in respiration is inhibited by KCN and phenylurethane in the concentrations which inhibit normal respiration. These concentrations are the same as those which inhibit growth. 5. From 2, 3, and 4, it seems possible that the increase in respiration caused by growth substance may be an essential part of its action in growth.     

植物源调节剂对玉米生长的影响

植物源调节剂是利用豆科和菊科植物为原料 ,首次研制的一种植物生长调节剂 ,对玉米萌发有促进作用 ,尤其表现在促进根生长。在苗期、拔节期叶面喷施 ,提高生物产量 2 1 4 3% ,增加千粒重 4 2 0g ,增产率2 1 95 %。使用浓度为 80× 10 -3 g/L或 10 0× 10 -3 g/L使用方法是拌种和苗期、拔节喷施     

THE EFFECTS OF GIBBERELLIC ACID AND KINETIN ON THE GROWTH OF MAJESTIC POTATO

The effects of spraying potato plants (var. Majestic) with gibberellic acid and kinetin were investigated. Gibberellic acid increased both leaf area and dry-matter production over the short period of the experiment, but there were indications that this would not persist at maturity. Kinetin alone depressed leaf area and dry-matter production, but this did not occur in the presence of gibberellic acid. The mean net assimilation rate measured over a 2-week period was not significantly reduced by gibberellic acid.     

LENGTH OF THE LIGHT-DARK CYCLE AND PLANT GROWTH

Tukey , H. B., Jr ., and H. J. Ketellapper . (California Inst. Tech., Pasadena.) Length of the light-dark cycle and plant growth. Amer. Jour. Bot. 50(2): 110–115. Illus. 1963.—It has been shown that the length of the light-dark cycle which causes maximal growth of tomato, pea, peanut, and soybean plants is close to 24 hr for cycles consisting of equal periods of light and darkness. The exact optimum for tomato plants was determined by temperature; the optimal cycle length was 20 hr at 30 C and 27–30 hr at 14 C. Such an interaction between temperature and cycle length was not found in pea plants, because peas were less sensitive to cycle length than peanuts, tomatoes, and soybeans and did not respond to changes in cycle length of 2–3 hr. The response to cycle length was not influenced by the conditions in which the seedlings had been raised prior to the treatment. Seedlings raised in a 16-hr light, 8-hr dark regime responded in the same manner as those raised in continuous light. The response to cycle lengths of 18, 24, 36, and 48 hr was not changed qualitatively by the temperature during the growth determination. Small changes in cycle length had no characteristic effects on the rates of photosynthesis, respiration or stem elongation. Stem elongation showed a rapid and initial increase in rate when the light was turned off. It was concluded that plants possess an endogenous time-measuring device with a period of 24 hr. For maximal growth to occur the external periodicity must be synchronized with the endogenous period of the plant. Efforts to obtain direct evidence for this hypothesis were not successful since no overt rhythms could be found in tomato plants.     

THE ROLE OF ZINC IN THE GROWTH OF PLANT TISSUE CULTURES

Klein , Richard M., Emerita M. Caputo , and Barbara A. Witterholt . (New York Bot. Gard., N. Y., N. Y.) The role of zinc in the growth of plant tissue cultures. Amer, Jour. Bot. 49(4): 323–327. Illus. 1962.—Zinc-sufficient and zinc-deficient auxin-auxotrophic callus and auxin-prototrophic crown-gall cultures of Parthenocissus tricuspidatus were examined for their growth capacity and ability to synthesize tryptophan. Growth capacity decreased rapidly when zinc ion was withheld and tryptophan synthetase activity in vitro was reduced. Growth of –Zn crown-gall tissues was stimulated by either auxin or tryptophan and growth of –Zn callus cultures was stimulated by tryptophan.     

THE RELATIONSHIP OF GIBBERELLIN AND AUXIN IN PLANT GROWTH

No synergism was found between IAA and gibberellin in the Avenucurvature test and this bioassay thus measures changes in diffusibleauxin resulting from gibberellin treatment and not a synergisticaction of the gibberellin on the curvature response to auxin.Gibberellin treatment causes an increase in diffusible auxinfrom the stem apex of dwarf pea (Pisum sativum L. var. LittleMarvel) 24 to 48 hours before the elongation response in thestem. The increase in diffusible auxin in the stem apex of Centaureacyanus L. var. Blue Boy occurs four to six days before the boltingresponse to gibberellin treatment under short days. The stemtissues of both the dwarf pea and Centaurea show an elongationresponse to IAA when the IAA is applied in a manner simulatingthe stem apex. Thus the growth of the dwarf pea and the boltingof Centaurea brought about by treatment with gibberellin aredependent on an increase in diffusible auxin. ¹Present address: Biological Institute, College of General Education,University of Tokyo, Komaba, Meguro, Tokyo.