EFFECT OF ETHYLENE ON CELLULAR DIFFERENTIATION IN ETIOLATED PEA SEEDLINGS

Ethylene (50 ppm) and 2,4-D (1 mm ) inhibit xylogenesis and completely prevent fiber lignification in the third internode of etiolated pea seedlings (Pisum sativum var. Alaska) during 96–240 hr of treatment. When ethylene is removed after 72 hr, normal differentiation resumes; thus the gas causes no irreversible damage to the cells. A combined treatment with 50 ppm ethylene and 50 μm 2,4-D or treatment with 1 mm 2,4-D alone causes inhibition similar to that observed with 50 ppm ethylene, and 50 μm 2,4-D is partially effective. The inhibition of xylogenesis and fiber lignification caused by 2,4-D is partly or wholly due to auxin-induced ethylene production.     

GROWTH PATTERNS OF PEA SEEDLINGS IN DARKNESS AND IN RED AND WHITE LIGHT

Thomson , Betty F., and Pauline Monz Miller . (Connecticut Coll., New London.) Growth patterns of pea seedlings in darkness and in red and white light. Amer. Jour. Bot. 48(3): 256–261. Illus. 1961.—Seedlings of peas were grown in vermiculite at 22°C. and exposed 16 hr. daily to red or white light or kept in darkness. Others were grown in soil in the greenhouse. Samples harvested daily to 16 days were dissected, the length of each internode and leaf measured and the total number of leaves and leaf primordia counted. The form of the stem apex and youngest primordia and interrodes is the same in light as in darkness. Leaf production is accelerated very slightly and the growth of leaves and internodes is decidedly accelerated by light. Leaf-leaf, leaf-internode and internode-internode correlations indicate that the morphogenetic effect of light is limited to later stages of organ growth. Dry weight is consumed more rapidly in light than in darkness, probably because of more rapid growth and slightly greater amounts of respiring tissue in light-grown plants.     

A MICROSCOPICAL STUDY OF THE STATOCYTE SYSTEM IN STEMS OF ETIOLATED PHASEOLUS SEEDLINGS

In etiolated bean seedlings there is a starch sheath around the vascular stem tissue. This cell layer shows a gradient of amyloplast number and cell dimensions. We demonstrated a maximum relative amyloplast pressure in the stem hook. Cytological as well as physiological arguments indicate that the stem hook may play an important role in graviperception through this starch sheath.     

EFFECT OF AUXIN AND ANTIAUXIN ON THE GROWTH AND RNA SYNTHESIS OF ETIOLATED PEA INTERNODE

Using etiolated Alaska pea internode segments the followingresults were obtained. An auxin, 2,4-dichlorophenoxyacetic acid, 1 mg/liter, inducedthe elongation growth of the segment and stimulated the biosynthesisof RNA, particularly of messengar RNA, in 3 hr incubation. Thesimilar stimulation of RNA synthesis and of elongation due toindole-3-acetic acid was found in 1 hr incubation. The stimulativeeffect of 2,4-dichlorophenoxyacetic acid on the elongation andon the synthesis of messenger RNA was inhibited by the additionof an antiauxin, transcinnamic acid. Significance of the auxin-inducedsynthesis of messenger RNA in producing protein responsiblefor the stress relaxation of cell wall is discussed. (Received June 13, 1967; )     

THE EFFECT OF COTYLEDON EXCISION ON THE GROWTH OF PEA SEEDLINGS

Pea plants grown under controlled conditions for 28 days were sampled nine times during this growth period. On each sampling day 80 plants were harvested. Cotyledons were excised from 40 plants and the root-shoot axis allowed to continue growth. The other 40 plants were divided into roots, shoots, and cotyledons; the dry weights of alcohol-water extracts and residues from these organs were determined. Shoot lengths, numbers of nodes, buds, flowers, and fruits of 28-day-old plants, whose cotyledons were excised at different times, were determined. These data indicate that cotyledon excision after the 13th day has no apparent effect on seedling growth, whereas excision before the 13th day reduces growth. Glucose-U-C¹⁴ supplied to attached cotyledons of 6- and 16-day-old seedlings resulted in no major difference in the distribution pattern of recovered label throughout the plant even though 16-day-old cotyledons were depleted of their normal endogenous food reserve.     

INTERACTION OF SUGARS AND AUXINS IN PEA EPICOTYL SECTION GROWTH

Purves , W. K., and A. W. Galston . (Yale U., New Haven, Conn.) Interaction of sugars and auxins in pea epicotyl section growth. Amer. Jour. Bot. 47 (8): 665–669. Illus. 1963.—The nature and magnitude of the response of “S₁” etiolated pea-epicotyl sections to auxin are determined by the concentration of sugar in the growth medium. For example, the concentration of IAA inducing maximum elongation shifts through at least 3 orders of magnitude in response to varying sucrose concentrations, from ca. 10^–4 M, with no sucrose, to 10^–7 M, with 2% sucrose. Similarly, the inhibitory action of high levels of IAA on elongation occurs only in the presence of sucrose. By contrast, although sucrose also promotes water uptake, it affects the IAA optimum for this process only slightly. The action of IAA on growth can be detected immediately, but the growth response to sucrose occurs only after a 6–8 hr. lag. If tissues are supplied with sucrose, then 1-hr. exposures to IAA can be as effective on growth as continuous 20-hr. exposures, depending on the time at which such exposures are given. Thus, 10^—4 M IAA applied in the presence of 2% sucrose is markedly inhibitory to elongation in hours 1–3, relatively inactive in hours 4–6, and strongly promotive after hour 7. The change from inhibitory to promotive action thus coincides in time with the length of the lag period for sucrose action.     

EFFECT OF GIBBERELLIC ACID ON ELONGATION AND NUCLEIC ACID SYNTHESIS IN ETIOLATED ALASKA PEA EPICOTYL

The following results were obtained using etiolated Alaska pea epicotyls. Gibberellic acid (GA) had the remarkable effect on the elongation in part I (elongating region) of epicotyls, whereas it had little effect on that in part II (mature region) of epicotyls. In cortex of part I and II of epicotyls, the cell number in longitudinal direction was hardly affected by GA. On the increase in width of epicotyls, GA was hardly effective in any parts of epicotyls. In both part I and II GA enhanced the incorporation of ³²P into all nucleic acid fractions prepared by methylated albumin kieselguhr (MAK) columns, i.e. sRNA, DNA and rRNA + mRNA. In part I the net increase in DNA and RNA content during the incubation period was slightly promoted by GA, whereas in part II the net decrease in both nucleic acids content was slightly promoted by GA. The relationship between GA-induced growth and nucleic acid synthesis is discussed.     

云南含笑苗期生物量及其相对生长关系的初步研究

本文比较研究了二种不同种源即贵州省威宁县河块乡树舍村和云南省安宁县绿乡官地村的云南含笑苗期的地径、苗高、根系、叶面积等因子生长状况及其生物产量;其次,分析了生物量以及各生长因子间的相互关系：第三．根据实际调查与测定数据拟合了关于生物量与各生长因子以及各器官生物量之间的３４个数学模型。文末拟定了云南含笑一年生苗木分级标准。     

ACRYLAMIDE GEL ELECTROPHORESIS OF SOLUBLE PLANT PROTEINS: A STUDY ON PEA SEEDLINGS IN RELATION TO DEVELOPMENT

The application of the technique of acrylamide gel electrophoresis to the separation of components of the soluble proteins of plants is described. The reproducibility of the results is demonstrated with reference to Neurospora proteins, and suitable procedures to document the results are described. These techniques have been applied to the soluble protein complement of segments along the axis of the root of Pisum sativum and of other parts of the seedling. The observations are interpreted in the light of current views on protein synthesis and cellular development.     

油菜素甾醇促进黄化水稻第二叶切段偏上性生长与乙烯的关系

油菜素甾醇强烈刺激黄化水稻第二叶切段倾斜的实质是偏上性生长。油菜素甾醇处理的切段的叶枕细胞带发生了不均一的可塑性生长,叶枕薄壁细胞明显增大。油菜素甾醇促进切段偏上性生长的同时伴随着乙烯释放。两促进效应能被乙烯生物合成抑制剂 CoCl_2平行抑制,表明两效应存在正相关。     

二苯基脲磺酸钙对小麦苗抗旱性的影响

用浓度为100mgL^-1的二苯基脲磺酸钙溶液喷小麦苗期叶片,能明显增加小麦幼苗的过氧化物酶、过氧化氢酶和超氧化物岐化酶的活性,并使保水力和复活能力增强。用100mgL^-1DSC拌种,还可提高小麦种子在干旱条件下的萌发率。