The effect of a cold treatment on the carbohydrate status of the scales and flower stalk of Tulipa gesneriana 1. cv Apeldoorn bulbs during growth after planting was studied and compared with bulbs not given cold treatment. Bulbs were stored dry for 12 weeks at 5'C (precooled) or 17°C (noncooled). Only the 5°C treatment led to rapid flower stalk elongation and flowering following planting at higher temperatures. Precooling enhanced mobilization of starch, fructans, and sucrose in the scales. The cold-stimulated starch breakdown was initially accompanied by increased a-amylase activity per scale. In noncooled bulbs, a-amylase activity slightly decreased or remained more or less constant. Cold-induced flower stalk elongation was partially accompanied by a decrease in the sucrose content and an increase in the glucose content and invertase activity per g dry weight. The starch content in internodes initially decreased and subsequently increased; a-amylase activity per g dry weight of the lowermost internode showed a peak pattern during starch breakdown and increased thereafter. The internodes of noncooled bulbs, on the contrary, accumulated sucrose. Their glucose content and invertase activity per g dry weight remained low. Starch breakdown was not found and a-amylase activity per g dry weight of the lowermost internode remained at a low level. Precooling of tulip bulbs thus favors reserve mobilization in the scales and flower stalk and glucose accumulation in the elongating internodes.It is well known that temperature controls the flowering process in many bulbous crops (Rees, 1972;De Hertogh and Le Nard, 1993). In the flowering process of tulips three phases have been distinguished: (a) the initiation phase, during which cell division and differentiation of the apical bud occur, resulting in the formation of a11 flower parts; (b) the preparation phase, during which the flower parts grow slowly and during which the conditions required for optimal flowering are prepared; and (c) the elongation phase, during which rapid extension growth of the shoot and flowering take place.In a temperate climate, flower initiation, flowering preparation, and shoot elongation occur in summer, winter, and spring, respectively. When bulbs are forced to flower at an earlier time, the cold winter period can be replaced by a welldefined, low-temperature treatment given to bulbs that are stored in climate rooms (dry-stored) (Rees, 1972;De Hertogh and Le Nard, 1993). Tulipa gesneriana L. cv Apeldoom bulbs require a dry-storage period of 12 weeks after planting at 5OC for optimal shoot elongation and flowering. The shoots of noncooled bulbs (dry-stored at 17OC) elongate slowly and, if anthesis is achieved, severe flowering disorders occur (Lambrechts et al., 1992).Experiments with exogenously applied GAs, GA biosynthesis inhibitors, and auxins showed that both GAs -and auxins are involved in the elongation process of the tulip flower stalk (Saniewski, 1989;Saniewski and Kawa-Miszczak, 1992). However, the sites of hormone action and the resu...
The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the leaf wax of three Plantago species were determined weekly for 3 weeks. The almost glabrous, free-standing leaves of Plantago major and the sparsely hairy Plantago lanceolata leaves were more heavily contaminated with low molecular weight (MW) PAHs (MW < 228) than the densely hairy, partly overlapping Plantago media leaves. This may be caused by the lower canopy roughness (higher aerodynamic resistance), the higher amount of leaf hairs (higher boundary resistance), and/or the higher leaf overlap (smaller accessible leaf area) of P. media. On the other hand, PAHs with MW ≥ 252 tended to show higher concentrations in P. media than in the other two species. This is likely caused by the dense layer of hairs on P. media leaves, which can efficiently intercept the largely particle-bound high MW PAHs. When the PAH concentrations were normalized to projected leaf surface area, the differences between P. media and the other two species became significant (p < 0.05) for the high MW PAHs, while the differences for the low MW PAHs decreased. Although the differences in PAH concentrations between species are relatively small (factor 2-5), this study clearly shows that plant architecture and leaf hairs influence the dry deposition of PAHs.
Arginine is the predominant free amino acid in the cotyledons of developing seeds of Pisum sativum L. cv Marzia. Breakdown of arginine was measured by injecting L-Iguanido-4Cjarginine into detached cotyledons. Cotyledons ofdeveloping seeds showed a low rate of 'C02 evolution whereas a much higher rate of '4("2 evolution was measured from cotyledons of seeds 4 days after the onset of germination. Arginine is an important N-storage compound in many higher plants. In developing pea seeds (4) and cotton seeds (5), arginine formation is considered to be located in the cotyledons themselves.The first steps of arginine degradation are catalyzed by arginase, OAT2, and urease yielding C02, NH3, and GSA. This pathway appears to be related to the transfer ofarginine-nitrogen to other amino acids and amides (18,27 A powder sample equivalent to 10 cotyledons was extracted with 80% (v/v) ethanol. After removal of ethanol by rotationevaporation, water was added to the residue to a final volume of 50 ml. Four ml of this extract was then shaken'with 4 ml CHC13 and centrifuged 10 min at 1000g. The water phase was carefully removed. Proteins in the water phase were precipitated by adding 1 ml of 10% (w/v) sulfosalicylic acid. The supematant obtained after precipitation was called the amino acid fraction. Arginine was determined by using an amino acid autoanalyzer (Biotronic LC 6000 E).Urea. Urea in the amino acid fraction was measured colorimetrically with diacetyl monoxime and thiosemicarbazide (21). Measurements were corrected for non-urea response caused by citrulline and arginine. Presence of urea from 0.05 ,mol/cotyledon can be demonstrated by using this assay.Protein Arginine. Proteins were extracted (1) from powder samples equivalent to five or more cotyledons, dependent on the stage of development. After grinding the sample with 50 mm Na2B407 and removal of cell debris by centrifugation 10 min-at 1000g, the proteins were collected by TCA precipitation (final concentration, 10% (w/v) TCA). The precipitate was washed twice with 5% (w/v) TCA and then twice with redistilled acetone. Protein hydrolysis occurred in 6 N HCI under N2 for 16 h. After removal of HCI under a stream of dry air at 100°C, arginine was determined colorimetrically (28) in the diluted (200 x) hydrolysate. The results concurred with determinations using an amino acid autoanalyzer.Nitrogen. The nitrogen content ofthe cotyledons, the extracted proteins, and the amino acid fractions were determined by using an elemental analyzer (Carlo Erba, model 1106
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.