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41.
At elevated atmospheric CO2 concentrations ([CO2]a), photosynthetic capacity (Amax) and root fraction (ηR, the ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible causes of this, focusing on the relative magnitudes of the effects of elevated [CO2]a on specific leaf (nm) and plant (np) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (α). In our survey of 39 studies with 35 species, we found that elevated [CO2]a led to decreased nm and np in all the studies and to increased h and α in most of the studies. The magnitudes of these changes varied with species and with experimental conditions. Based on a model that integrated [CO2]a-induced changes in leaf nitrogen into a biochemically based model of leaf photosynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (Amax will increase) when growth at increased [CO2]a leads to increases in h that are larger than decreases in nm. Photosynthesis will be downregulated (Amax will decrease) when increases in h are smaller than decreases in nm. The model suggests that photosynthetic capacity increases at elevated [CO2]a only when additional leaf mesophyll more than compensates the effects of nitrogen dilution. We considered two kinds of regulatory paradigms that could lead to varying responses of ηR to elevated [CO2]a, and compared the predictions of each with the data. A simple static model based on the functional balance concept predicts that ηR should increase when neither np nor h is very responsive to elevated [CO2]a. The quantitative and qualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts ηR from the relative sensitivities of photosynthesis and relative growth rate to elevated [CO2]a corresponds much more closely to the observations. In general, root fraction increases if the response of photosynthesis to [CO2]a is greater than that of relative growth rate. 相似文献
42.
Plant regenerated organs such as shoots, bulbs, microtubers, corms, embryos, etc. have been successfully proliferated in the bioreactor. The use of a bioreactor leads to the development of technology suitable for large scale plant propagation. The basic construction and characteristics of various types of bioreactor systems are reviewed in relation to shoot and embryo cultures. A pilot scale 500 liter bioreactor system was applied to the production of large scale Stevia rebaudiana shoots.Abbreviations DW
dry weight
- EC
electrical conductivity
- FW
fresh weight
- ORP
oxidation-reduction potential 相似文献
43.
Nobuyuki Uozumi Yurie Asano Takeshi Kobayashi 《Plant Cell, Tissue and Organ Culture》1994,36(2):183-190
Adventitious shoot primordia were formed on horseradish hairy root cultured in dark. Plantlet formation frequency from the primordia was higher than that from root fragments. Culture for 26 days provided the adventitious shoot primordia, which had the highest potential for plantlet formation (53% explants at 40 days). Benzyladenine supplementation in the dark caused primordium enlargement, but did not increase the number of primordia formed. After adventitious shoot primordia were encapsulated with calcium alginate, kinetin supplementation (2.0–4.0 M) increased the shoot formation frequency (65–80% explants at 20 days) in the light, but also promoted the undesirable formattion of multiple shoots. Supplementation with naphthaleneacetic acid (0.27–5.4 M) in the calcium alginate beads in light enhanced the root emergence from primordia without inhibition of plantlet formation when the encapsulated beads were put on the agar-medium without naphthaleneacetic acid. 相似文献
44.
Hanns Ulrich Seitz Dorothea Elisabeth Gärtner 《Plant Cell, Tissue and Organ Culture》1994,38(2-3):337-344
In contrast to undifferentiated cell suspension cultures of Digitalis lanata, photomixotrophic shoot cultures of Digitalis purpurea accumulate cardiac glycosides in substantial concentrations. They are used to investigate enzymes of the cardenolide pathway. All cardenolides are 5-configurated. The progesterone 5-reductase and the 3-hydroxysteroid-5-oxidoreductase are present in shoot cultures but not in undifferentiated cell cultures. These enzymes provide precursors for cardenolides, whereas the presence of the progesterone 5-reductase, also present in shoot cultures, is discussed with regard to its role in phytosterol biosynthesis and may be attributed to the general steroid pathway. The progesterone 5-reductase had an activity maximum during the early growth period seven days after onset of cultivation, whereas the corresponding progesterone 5-reductase activity was highest on day 11. The maximum cardenolide accumulation was after 24 days. The enzyme activities present in crude extracts from shoot cultures were characterized with regard to their requirements for NADPH and NADH, pH-optimum, temperature optimum, affinity to their substrates and their localization in the cell. The progesterone 5-reductase was purified 769-fold.Abbreviations DW
dry weight
- FW
fresh weight
- PVP
polyvinylpyrrolidone 相似文献
45.
M. A. Perez-Parron M. E. Gonzalez-Benito C. Perez 《Plant Cell, Tissue and Organ Culture》1994,37(3):297-302
Micropropagation of Fraxinus angustifolia Vahl has been successfully achieved both from mature and juvenile plant material using shoot tip and nodal explants. Several basal media supplemented with benzyladenine (BA) and indolebutyric acid (IBA) were tested for shoot proliferation. The most new explants per mature explant (5.3) was obtained on DKW medium plus 4.4 M BA+0.98 M IBA. The most new explants per juvenile explant (5.6) was produced on QL medium plus 8.9 M BA+0.49 M IBA. Rooting was achieved on WPM supplemented with 0.98–4.9 M IBA. Rooted plantlets were transferred to soil and acclimatized with 85% survival.Abbreviations BA
benzyladenine
- IBA
indolebutyric acid
- NAA
1-naphthaleneacetic acid 相似文献
46.
Carolina Martinez Pulido Indra S. Harry Trevor A. Thorpe 《Plant Cell, Tissue and Organ Culture》1994,39(3):225-230
Three-day-old cotyledonary explants of Pinus canariensis were subjected to 30 induction treatments using half-strength Bornman's medium containing various combinations of N6- benzyladenine, zeatin, kinetin and 2-isopentenyl-adenine. The highest numbers of buds were obtained with 10 M 6-benzyladenine, but both kinetin and zeatin influenced shoot elongation. Shoots were maintained on half-strength Schenk and Hildebrandt medium with 2% sucrose and 0.05% activated charcoal. For rooting, shoots were pulsed for 4 h in a 100 M indole-3-butyric acid aqueous solution (pH 4.2–4.5), and planted in peat:vermiculite:perlite (1:1:1). After 8 weeks, the numbers of rooted shoots were similar for most treatments. Therefore, the bud induction treatments did not significantly influence rooting of adventitious shoots of Canary Island pine. 相似文献
47.
The effects of the acylcyclohexanedione-type growth retardant prohexadione calcium on seedling growth and endogenous levels of immunoreactive phytohormone-like substances in shoots of wheat ( Triticum aestivum L. cv. Kanzler) and oilseed rape ( Brassica napus L. ssp. napus cv. Lirajet) were studied. After treatment of seedlings with increasing retardant concentrations in hydroponics, plant height and fresh weight of shoots were reduced by up to 40%. Concomitantly, the amount of immunoreactive gibberellins decreased, on a fresh weight basis, when compared with levels in the shoots of control plants. In contrast, the levels of abscisic acid and dihydrozeatin riboside and isopentenyladenosine-type cytokinins were considerably elevated by the growth retardant. The content of 3-indoleacetic acid decreased slightly. These results suggest that, in addition to its effect on gibberellin content, prohexadione calcium also influences the levels of endogenous abscisic acid and cytokinins. 相似文献
48.
49.
纵坑切梢小蠹蛀梢期空间分布 总被引:10,自引:1,他引:9
在昆明地区,纵坑切梢小蠹(Tomicus piniperda)成虫蛀梢多集中在蛀干木附近。 种群密度以蛀干木为中心向周围呈指数递减,散布半径约30m。在蛀梢过程中,该种群逐渐向新区扩张。在树冠内,纵坑切梢小蠹主要分布在4-10轮枝上。第7轮枝虫口百分率最高。6-7轮枝受害率最大。 树冠上层受害较其下层严重。从树冠水平层次考察,树冠外层虫量相对集中,约为树冠中、内层虫量之和。 树冠内层虫量最少。纵坑切梢小蠹在树冠内的种群分布系由梢径、种群密度、蛀梢行为、降落方式、光照等因素综合影响的结果。 相似文献
50.