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71.
The gas exchange properties of whole plant canopies are an integral part of crop productivity and have attracted much attention
in recent years. However, insufficient information exists on the coordination of transpiration and CO2 uptake for individual leaves during the growing season. Single-leaf determinations of net photosynthesis (Pn), transpiration
(E) and water use efficiency (WUE) for field-grown cotton (Gossypium hirsutum L.) leaves were recorded during a 2-year field study. Measurements were made at 3 to 4 day intervals on the main-stem and
first three sympodial leaves at main-stem node 10 from their unfolding through senescence. Results indicated that all gas
exchange parameters changed with individual main-stem and sympodial leaf age. Values of Pn, E and WUE followed a rise and
fall pattern with maximum rates achieved at a leaf age of 18 to 20 days. While no significant position effects were observed
for Pn, main-stem and sympodial leaves did differ in E and WUE particularly as leaves aged beyond 40 days. For a given leaf
age, the main-stem leaf had a significantly lower WUE than the three sympodial leaves. WUE's for the main-stem and three sympodial
leaves between the ages of 41 to 50 days were 0.85, 1.30, 1.36 and 1.95 μmol CO2 mmol−1 H2O, respectively. The mechanisms which mediated leaf positional differences for WUE were not strictly related to changes in
stomatal conductance (gs·H2O) since decreases in gs·H2O with leaf age were similar for the four leaves. However, significantly different radiant environments with distance along
the fruiting branch did indicate the possible involvement of mutual leaf shading in determining WUE. The significance of these
findings are presented in relation to light competition within the plant canopy during development. 相似文献
72.
The role of allelopathy in citrus replant problems was investigated in Iraq. The failure of citrus seedlings to grow normally in old citrus orchards was not caused by differences between old and non-citrus soils in electrical conductivity, pH, organic matter, soil texture and those minerals tested. Extracts of soil collected from old citrus orchards significantly reduced the growth of sour orange seedlings. Extracts and decaying sour orange roots reduced the growth of sour orange seedlings as did extracts of non-senescent sour orange leaves and decaying senescent leaves. Thus it appears that allelopathy is at least partly involved in the citrus replant problem. 相似文献
73.
H. V. Cornell 《Evolutionary ecology》1989,3(1):64-76
Summary Endophagous folivores, which are concealed inside leaf tissue for much of their life cycle, or which live externally but feed internally, should be more successful on heavily defended plants than ectophagous species. This is because endophages are more facile at feeding selectively and can manipulate tissue development to avoid physical and chemical defenses and to enhance nutrition. As a result, endophage-ectophage ratios should increase on more heavily defended hosts. This pattern will likely be strengthened by negative asymmetrical interactions with ectophages and pathogens, which may displace endophages from lightly defended hosts. The hypothesis predicts that endophages should be particularly abundant in resource-poor habitats which seem to support a preponderance of heavily defended hosts. Although data do not yet exist for a rigorous test, several observed cases where endophage distributions seem biased toward heavily defended hosts are at least consistent with the hypothesis. Plant defense levels may have little influence on the total number of herbivores associated with a host, but I suggest that guild structure can be profoundly altered. 相似文献
74.
Abstract. The authors have previously shown that cell treatments causing intra-cellular alkalinization stimulate the in vivo phosphorylation of a 33-K Dalton polypeptide (33 KP) (Tognoli & Basso, 1987). Here, the authors report that this polypeptide belongs to a protein associated with the microsomal membranes. They show that treatment of cells which induce intracellular alkalinization stimulate 33-KP phosphorylation, whether the phosphorylation is performed in vivo (cells loaded with 32 Pi before treatments) or in vitro (microsomes from control and treated cells, incubated with γ32 P ATP). In both cases, 33 KP is phosphorylated on a serine residue. Microsomes do not show any phosphatase activity towards this phosphorylated protein, indicating involvement of a protein kinase reaction as an effector of changes induced by intracellular alkalinization. The number of phosphorylated sites or molecules of this protein increases as a result of intracellular alkalinization, suggesting that intracellular alkalinization causes topological or conformational modifications to a protein kinase or its substrate protein. The in vitro phosphorylation is not specifically influenced by the pH of the in vitro phosphorylation medium, suggesting that protein phosphorylation is not directly controlled by cytoplasmic pH. 相似文献
75.
76.
Kees W. Rodenburg Marcel J. A. de Groot Rob A. Schilperoort Paul J. J. Hooykaas 《Plant molecular biology》1989,13(6):711-719
In relation to the question which DNA form (single- or double-stranded) is transferred by Agrobacterium tumefaciens to plant cells, we studied the behaviour of single-stranded DNA, as compared to double-stranded DNA, when it is introduced into plant protoplasts by electroporation. To this end, we cloned a construct with a plant NPTII gene as well as a CAT gene in the M13 vectors tg130 and tg131. We found that both complementary single-stranded molecules gave rise to substantial CAT activity in plant protoplasts, suggesting that single-stranded DNA is converted into double-stranded DNA by the plant cell replication machinery. Unexpectedly, we found that single-stranded DNA leads to a 3–10 fold higher frequency of stable transformation (selection for kanamycin resistance) than double-stranded DNA. These results indicate that the use of single-stranded DNA might be considered in experiments in which optimal transformation frequencies are needed, e.g. with protoplasts form recalcitrant plant species.Abbreviations ss
single-stranded
- ds
double-stranded
- CAT
chloramphenicol acetyl transferase
- NPTII
neomycin phosphotransferase II
- RT
room temperature 相似文献
77.
D. Q. Binh L. E. Heszky G. Gyulai E. Kiss A. Csillag 《Plant Cell, Tissue and Organ Culture》1989,18(2):195-200
Callus was induced from seeds of Puccinellia distans (L.) Parl. on MS medium supplemented with 2 mgl-1 2,4-dichlorophenoxyacetic acid and 0.5 mgl-1 kinetin. Morphogenesis initiation was achieved during subculture on medium containing 0.1 mgl-1 2,4-D. From the point of morphogenetic capacity, 3 types of callus were selected. High frequency of plant regeneration was obtained by selection of embryogenic type of callus, and culture on N6 medium and N6 medium supplemented with kinetin (5–10 mgl-1), or kinetin (2 mgl-1) and IAA (0.5 mgl-1). A high ratio of albinos among regenerants was observed. 相似文献
78.
In the last twenty-five years, young inflorescences, floral buds and individual floral organs of a number of species have been cultured in vitro. There is considerable variability in the requirement of plant growth regulators and nutritional factors for flower development of different species. This variability is compounded by the fact that the hormonal and nutritional requirements are different at various stages of organ and floral development. Experimental studies on normal and mutant flowers in vitro have provided insights into some of the regulatory processes in floral organogenesis. The potential use of the in vitro technique in elucidating the various mechanisms in flower development is stressed. 相似文献
79.
Calli from hypocotyl and root explants of Digitalis obscura L. showed regeneration of adventitious shoots, roots and embryos when transferred to Murashige & Skoog medium supplemented with cytokinins alone or in combination with auxins. Optimum shoot-bud formation was achieved in the presence of IAA and BA, while roots mainly appeared either in absence of growth regulators or with IAA and Kn. Embryo formation took place only in those combinations that included Kn. Embryo development was influenced by the type of auxin, and precocious germination occurred in media with NAA. Mechanically isolated cells from hypocotyl- and root-derived calli were plated in MS medium supplemented with several IAA and BA combinations. Single cells were able to proliferate forming callus within 20–30 days in culture. In order to induce organogenesis, calli were transferred to various regeneration media. Shoot-bud differentiation efficiency depended on both callus origin and medium initially used for cell culture, best results being obtained in calli grown from hypocotyl-derived cells cultured in the presence of casein hydrolysate. A further subculture to medium containing coconut milk and lower concentrations of NH4NO3 and sucrose promoted shoot development. Rooting was readily achieved upon transferring shoots onto half-strength MS medium. Plantlets were ultimately established in soil.Abbreviations BA
benzyladenine
- BM
basal medium
- CH
casein hydrolysate
- CM
coconut milk
- 2,4-D
2,4-dichlorophenoxyacetic acid
- IAA
indoleacetic acid
- Kn
kinetin
- MS
Murashige & Skoog
- NAA
naphthaleneacetic acid 相似文献
80.
Protoplast cultures were prepared from hypocotyls of ten spring rapeseed cultivars. Protoplasts from all genotypes tested formed calli, and shoots were regenerated from calli of nine of the genotypes at frequencies varying from 15 to 76%. The regenerating cultivars fell into a high regenerating group (>60% and a low regenerating group <25%). 相似文献