Cut End Of Stem Research Articles

Effect of Water Status on Dendrobium Flower Spray Postharvest Life

The postharvest life of Dendrobium spp. flower sprays was limited by wilting and shedding of individual “flowers. Late-summer-harvested sprays had a reduced postharvest life compared to winter-harvested sprays. Cultivars differed in postharvest life in response to packing and storing for 2 days at 22C. Water 10ss rates of `Princess' sprays continuously held in deionized water declined from ≈ 1.25 g/day per spray 4 days after harvest to 0.35 g/day per spray 20 days later. Flower shedding occurred when the rate of water loss fell below ≈1.0 g/day per spray. Addition of a floral preservative to the vase water slowed the decline in water loss and increased postharvest life. Sprays packed and stored for 6 days at 22C had half the postharvest life of nonpacked controls held in deionized water or of sprays packed for 2 or 4 days at 22C. Submerging sprays in water immediately after harvest did not significantly increase postharvest life; submerging the sprays after harvest, before packing, and again after unpacking reduced postharvest life. Sprays could not be held for more than 4 days at 10C without suffering chilling injury. Silver thiosulphate (2 mm) and other silver preparations had no effect on postharvest life, although silver ions did reach the top flowers of the spray; thus, ethylene may play only a minor role in spray postharvest life. The postharvest life of sprays was increased by using boiled deionized water in vase solutions and by the continuous presence of chloramphenicol. Other antimicrobial agents, such as Physan, sodium hypochlorite, and sodium dichloro-s-triazinetrione dihydrate were without effect. Microbial growth in the vase solution and at the cut stem end mav have reduced water transport and induced subsequent flower wilting and shedding.

Biogenesis of the C-Glycoside leucodrin in Leucadendron Argenteum

Abstract Biogenetic pathways for leucodrin formation in Leucadendron spp. are discussed and were tested by feeding labelled d -galactose, d -glucose and l -ascorbic acid to cut stem ends of L. argenteum . It was shown that the two aldohexoses are better precursors and preferentially incorporated into that portion of leucodrin derivable from p -coumaric acid. When this route is suppressed by feeding the labelled sugars in the presence of a large amount of phenylalanine) label is predominantly incorporated in the carbohydrate part of leucodrin. The biogenesis of leucodrin therefore may proceed via coupling of l -galactono-γ-lactone and p -coumaric acid.

Formation of Adventitious Buds in Decapitated Citrus Seedlings and the Effect of Some Growth Regulators

Young seedlings of various citrus species give rise, after decapitation, to adventitious buds at the cut end of the epicotyl. With such treatment, more buds formed on seedlings of sweet orange, sour orange, and grapefruit than of lemon, mandarin, and calamondin. Anatomical observations at the cut stem end show formation of buds occurring from tissues close to the cambium. Growth regulators applied at the cut epicotyl end modified the patterns of bud formation. 6-Benzylaminopurine (BAP) promoted bud formation; indole-3-butyric acid (IBA), abscisic acid (ABA), and gibberellic acid (GA3) inhibited it. BAP reversed the inhibitory effect of GA3. Gibberellic acid caused a typical elongation of the sprout axis. The use of decapitated seedlings as a tool for studying stem differentiation in citrus is suggested.

Studies on the Ammonium Tolerance of Some Cultivated Solanaceae1,2

Abstract Tomato, tobacco, pepper, petunia, and eggplant were screened for their tolerance to continuous (NH4)2SO4 applications. Stem lesions, analogous to those which appear on tomato during ammonium toxicity, were formed on eggplant but not on the other species. Of the plants tested, tobacco was the most tolerant to applications of (NH4)2SO4. Potassium applications increased the ammonium concentration of tobacco tissues but lowered the ammonium concentration of tomato tissues. Diamine concentrations were increased by the application of (NH4)2SO4. The application of KCl decreased the putrescine concentration of tobacco and increased the concentration of cadaverine in tomato and tobacco. The application of putrescine-2HC1 in aqueous solution to cut stem ends of axillary shoots of tomato and tobacco induced the formation of stem lesions analogous to those formed by the (NH4)2SO4 fertilization of tomato. It is postulated that the tolerance of tobacco to stem lesion formation is related to putrescine utilization in nicotine synthesis.

Studies on Polyoxins, Antifungal Antibiotics

Polyoxin is the antibiotic having extensive activities against various fungi, especially, Alternaria spp.Tests were carried out to evaluate fungicidal activities of Polyoxin against Alternaria mali and Alternaria kikuchiana in vitro and in vivo.Among Polyoxin A, B, D, F, G fractions, B fraction especially inhibited development of mycelium, spore germination and sporulation. G fraction showed the high activity in vitro test, but low activity in vivo test. On the one hand, A and D fractions showed the reverse tendency.All fractions of Polyoxin caused abnormal bulbous phenomenon on germ tube of spore and mycelium at low concentration.Polyoxin complex permeated little into spore. Therefore, Polyoxin did not inhibit spore germination at the usual concentration, but made bulbing germ tube as soon as spore germinated.Antisporulation activity of Polyoxin was very strong and kept for a long time.Results of Field test showed that Polyoxin is more effective than the compared fungicides.Polyoxin penetrated into apple leaf and was absorbed from the cut end of apple stem.

Studies on Polyoxins, Antifungal Antibiotics

Polyoxins, antifungal antibiotics produced by Streptomyces cacaoi var. asoensis, are consisted of many active fractions such as A, B, D, E, F, G and etc., and have antifungal activities selectively against several plant pathogenic fungi. In this paper, fungicidal activities of Polyoxins against sheath blight of rice Pellicularia sasakii (Shirai) S. Ito, and behaviours in plant tissue were investigated.Among many active fractions, D fraction was the most effective for control of this disease. In vitro, Polyoxin complex was more active than organic arsenic compounds and other fungicides against the fungus. In the pot test in greenhouse, Polyoxin complex showed the same protective effect and the same inhibitory effect on development of lesion as methanearsonic acid-ferric, ammonium salt complex. Treating on rice plants, Polyoxin complex showed about the same stability for ultra violet as those of organic arsenic compounds.By bioassay method, it was recognized that Polyoxin complex penetrated into leaves of kidney bean from back side to surface and sheaths of rice plants from surface to tissue inside. Dipping the cut end of stem of kidney bean and no wounded root of rice plant into the solution of Polyoxin complex, a remarkable amount of Polyoxin complex was found to be absorbed and translocated. Being treated by Polyoxin complex on sheaths of rice plant, no rising of active fraction of Polyoxin was observed in the upper part of no wounded sheaths or diseased sheaths of rice plants, but a remarkable amount of active fraction of Polyoxin was observed in the upper of sheaths which were injured by needle prick method. We could not obtain any definite results of penetration of Polyoxin complex into mycelium of sheath blight of rice plant.

Absorption and Translocation of Boron by Sunflower Plants

The absorption and translocation of boron by sunflower plants (Helianthus annuus L.) grown under controlled-environment conditions were investigated. Exudates in a 43-hr period from the cut stem ends of the root systems of detopped plants contained the same amount of boron whether the roots were immersed in nutrient solutions containing 500 μg or 1,000 μg of boron per liter. Plants given a total of 60 μg of boron in the substrate, but in varied amounts and times of application, showed no differences among the treatments in the accumulation of boron by their mature leaves. Two of the four series with multiple application, however, showed delays in the onset of severe symptoms of boron deficiency as compared with the series with an initial single 60-μg application. Significant lateral transport of boron occurred at the stem tip and in leaf blades when boron was supplied to only half of a split root system at 500 or 1,000 μg per root-half. Slight, though not significant, lateral transport occurred across the lower levels of the stems in these series. Lateral transport of boron at the lower internodes was demonstrated when boron was supplied to only one-half of the root system in higher quantities (5,000 or 10,000 μg per root half). Little or no lateral transport in leaves or stems was observed with boron application of 50 or 100 μg per root-half. Although mature leaves sprayed with 10-ppm boron solution (as boric acid) showed an increase in dialyzable boron content, this soluble boron was not translocated from the leaves. No differences in growth were evident between plants receiving dialyzable boron extracted from leaf tissues and those receiving boric acid in the nutrient solutions. Non-dialyzable boron in the non-particulate fraction of leaf homogenate, however, was not utilized by plants when it was added to the nutrient solution. Reversing the transpiration stream of a leaf by placing it in a dilute minus-boron nutrient solution and withholding a water supply from other organs of the plant did not result in a movement of boron from the leaf to the apical meristem. Some of the boron in the leaf, however, was readily leached into the nutrient solution. Covering the top surface of a leaf with aluminum foil to limit photosynthesis did not result in a change in its boron content. A nitrogen-deficient nutrient solution adversely affected the capacity of plants to accumulate boron. From the results of the experiments described, it is concluded that one of the prime factors controlling the distribution of boron in sunflower plants is the extent and location of the metabolic requirement for this element. It is further proposed that immobility of boron in the leaves of this species results from some type of translocation block in the vascular tissue and not from a fixation of boron in a soluble but non-utilizable form.

Physiological studies on adventitious root formation in cuttings of Portulaca grandiflora HOOK. II

1. A root promoting substance (or substances) was demonstrated in the leaves of Portulaca. This substance moved from leaf to the cut end of stem cutting after the stem was cut.2. The substance moved more slowly from leaf to stem in darkness than in light, but the movement of substance itself doesn't require light.3. The rooting substance was detected in higher concentration in the leaves just after cutting, and decreased there after, transferring to the base of stem.4. Root promoting powers of sucrose, IAA, IBA, 2, 4, 5-TP and kinetin were compared with that of the substance in Portulaca leaves, and their similarity to the substance was discussed.