Light on phloem transport (an MRI approach)
Prusova, Alena - \ 2016
Wageningen University. Promotor(en): Herbert van Amerongen, co-promotor(en): Henk van As. - Wageningen : Wageningen University - ISBN 9789462579156 - 130
solanum lycopersicum - phloem - light - flow - photoperiod - nuclear magnetic resonance - biophysics - magnetic resonance imaging - solanum lycopersicum - floëem - licht - stroming - fotoperiode - kernmagnetische resonantie - biofysica - kernspintomografie
This thesis (Light on phloem transport – an MRI approach) aims to answer the question whether phloem transport can be a limiting factor for photosynthesis efficiency (and ultimately causing a bottleneck towards achieving higher yields). To answer this key question, we manipulated the source: sink ratio within tomato (Solanum lycopersicum L.) while measuring phloem transport with magnetic resonance imaging (MRI) flowmetry. Additionally we compared phloem flow characteristics of two potato plants (Solanum tuberosum L.) which differed in source : sink ratio. In Chapter 2, the source strength was manipulated by varying the light intensity. An increase in phloem sap volume flow under higher light intensities was observed. However, under all light intensities applied, the phloem flow velocity was found to be constant (as has previously been suggested in other studies) although a clear diurnal pattern was observed. This finding does not fit in current models to describe the mechanism of phloem transport and a different mechanism must be at play. The results of this chapter demonstrate that increased levels of photo-assimilates are transported in sieve tubes, which are activated when needed by the plant. This is the first study which shows that plants activate individual sieve tubes when more photo-assimilates are available, yet maintain constant velocity. Those observations were in a tomato plant with pruned fruit trusses (i.e., in a simplified system). In Chapter 3, we investigated whether tomato plants still exhibit constant phloem flow velocity (with a diurnal pattern) under normal conditions, i.e., with strong sinks (tomato fruits) still attached. This was tested for both a long and short photoperiod by measuring flow characteristics with MRI flowmetry. We simultaneously monitored other plant processes like xylem flow rates with a heat balance sensor, net photosynthesis with gas exchange and stem diameter changes with a linear motion potentiometer. With this integrated approach, we revealed a correlation between night phloem volume flow, dark respiration and stem growth. We also conclusively showed that phloem volume flow performs a diurnal pattern under a variety of source-sink ratios which appears to be a normal behaviour for tomato plants growing under moderately-high light conditions. In chapters 2 and 3 we learned that under higher source strength a greater amount of phloem sap is transported, but the changes in flow were not accompanied by changes in velocity. To further our understanding of the mechanisms driving phloem transport, it is of interest to know how the sucrose concentration in phloem sap relates to phloem flow. In Chapter 4 we used an average T2 relaxation time in the phloem vascular tissue region to reveal the plant’s phloem carbon status under source manipulation. In this chapter we demonstrated that T2 relaxation time, when measured in parallel with phloem flow, can provide additional information about phloem region carbon status, i.e., changes in the T2 relaxation time are correlated with changes in sucrose concentration in the whole phloem region.
When studying phloem transport in plants with magnetic resonance imaging (MRI) flowmetry, plants which are relatively easy to manipulate (e.g. fruit pruning) like tomato have so far been used. However, tomato plants (used in all three previous chapters) have relatively low sink strength beneath the MRI measurement site. A potentially preferable approach is to work with plants with strong sinks beneath the measurement site. In Chapter 5 we studied potato as a potentially better test subject for MRI flowmetry as it possesses strong sink below the MRI measurement site (i.e., developing tubers). For that purpose we used two potato plants (cv. Desiree) both with several developing tubers. One of the plants overexpressed the StSWEET gene (35S:StSWEET) which appears to have altered its source : sink ratio. As a result, the 35S:StSWEET plant transported 60% more phloem sap than Desiree WT. Strikingly, the average phloem flow velocity in both plants was the same and the greater amount of transported phloem sap in the 35S:StSWEET plant was accommodated by more sieve tubes than in Desiree WT. This finding agrees with the hypothesis about the conserved nature of phloem flow velocity, where volume flow is regulated by the number of active sieve tubes (Chapter 2 and 3). In this chapter we also demonstrate that a potato plant with developing tubers represents a good subject to study phloem transport with MRI flowmetry. We concluded that under optimal conditions (which are commonly met in greenhouses) phloem transport is likely to reach its maximum capacity and therefore photosynthesis could be limited by the export and transport of photo-assimilates because of the finite number of sieve tubes and constant flow velocity.
Nuclear magnetic response imaging of sap flow in plants
Windt, C.W. - \ 2007
Wageningen University. Promotor(en): Herbert van Amerongen; T.J. Schaafsma, co-promotor(en): Henk van As. - [S.l.] : S.n. - ISBN 9789085047292 - 172
sapstroom - kernmagnetische resonantie - transport over water - floëem - ricinus communis - sap flow - nuclear magnetic resonance - water transport - phloem - ricinus communis
This thesis deals with Nuclear Magnetic Resonance (NMR) imaging of long distance transport in plants. Long distance transport in plants is an enigmatic process. The theoretical framework that describes its basic properties has been in place for almost a century, yet at the same time only little is known about the dynamics of long distance transport inside the living plant. The latter is caused by the fact that the two pathways in which transport takes place, the xylem and the phloem, are virtually inaccessible to invasive experimentation. As a result a wide range of questions about the dynamics of long distance transport have yet to be answered. Examples of such questions, as addressed in this study, are: how fast does phloem sap move; how variable is the phloem sap flow velocity between species and over the diurnal cycle; what percentage of the potential flow conducting area in xylem tissue is functional. Or with regard to fruits: what percentage of the influx to fruits occurs through the xylem, what percentage through the phloem; does the xylem remain functional throughout fruit development; and does backflow from the fruit to the plant occur. Here, we show that NMR flow imaging provides a non-invasive and quantitative means to answer these intriguing questions.
Stiletpenetratie door bladluizen
Tjallingii, W.F. - \ 2003
Entomologische Berichten 63 (2003)5. - ISSN 0013-8827 - p. 110 - 116.
aphidoidea - voedingsgewoonten - floëem - sapstroom - plantenweefsels - aphidoidea - feeding habits - phloem - sap flow - plant tissues
Stylet penetration by aphids can be studied well by the electrical penetration graph (EPG) technique, a recording system which incorporates both plant and insect in an electrical circuit. A large number of details of plant-aphid interactions during stylet penetration has been elucidated by EPG-studies
Tentative determination key to 600 trees, shrubs and climbers from the Ivory Coast, Africa, mainly based on characters of the living bark, besides the rhytidome and the leaf
Outer, R.W. den - \ 1972
Wageningen : Veenman (Mededelingen Landbouwhogeschool 72-18,19,20,21) - 4
planten - identificatie - bedektzadigen - bosbouw - bomen - floëem - schors, bomen - plantenmorfologie - ivoorkust - bladeren - plantenfysiologie - plants - identification - angiosperms - forestry - trees - phloem - bark - plant morphology - cote d'ivoire - leaves - plant physiology
Movement of 45Ca in the phloem of Yucca
Wiersum, L.K. ; Vonk, C.A. ; Tammes, P.M.L. - \ 1971
Wageningen : [s.n.] (Publication / Plant physiological research centre no. 104) - 2
floëem - liliaceae - yucca - calcium - voedingsstoffen - metabolisme - plantenvoeding - assimilatie - phloem - liliaceae - yucca - calcium - nutrients - metabolism - plant nutrition - assimilation
Histological investigations of the secondary phloem of gymnosperms
Outer, R.W. den - \ 1967
Wageningen University. Promotor(en): A.L. Stoffers. - Wageningen : Veenman - 118
bosbouw - bomen - naaktzadigen - floëem - cytologie - plantenweefsels - forestry - trees - gymnosperms - phloem - cytology - plant tissues
An anatomical study of secondary phloem of the different species of Gymnosperms showed that three categories could be distinguished, which may represent three evolutionary stages. These three categories were:Pseudotsuga taxifolia type, to which belong many Pinaceae (while the other Pinaceae species belong to a subtype, e.g. the Tsuga canadensis subtype);Gingko biloba type, to which belong the Cycadaceae, Araucariaceae and many Podocarpaceae and Taxaceae;Chamaecyparis pisifera type, to which belong the Cupressaceae, Taxodiaceae and the rest of the Taxaceae and Podocarpaceae.The phylogenetic sequence of the axial system and the reduction of the phloem rays starts in the Ps. taxifolia type with an almost uniform axial system and ray- albuminous cells, and a complex heterogeneous phloem ray, differentiating through the G. biloba type to the C. pisifera type, which has a highly specialized axial system with phloem-albuminous cells and a simpler, reduced homogeneous phloem ray. The reduction of the phloem rays parallels the differentiation of the axial system.
Onderzoek naar bruikbare kenmerken ter identificatie van boomen naar hun bast
Thorenaar, A. - \ 1926
Wageningen University. Promotor(en): E. Reinders. - Wageningen : Veenman - 207
bosbouw - floëem - schors, bomen - nederlands indië - cum laude - forestry - phloem - bark - netherlands east indies
To facilitate further discussions and to inform tropical forestry experts, the formation and anatomy of bark were reviewed in association with its terminology. Sections deal with: secondary phloem; dilation and sclerosis; their influence on primary bark parts and on secondary phloem; interxylary phloem; pith ducts; periderm; lenticels and dead outer bark. Next follows an analysis of what could usually be seen of the anatomy of the bark and the crust with a x 10 lens and with the naked eye. The features noticed were then evaluated as distinctions for bark species. Information was given on odour and taste.
Then follow descriptions of 60 investigated barks of the Indonesian Archipelago, analysed by these means. A x 10 lens proved sufficient for identification.
The sequence of bark features from common to special features was shown to be usually: cork layer, stone cells, fibres, soft bark parts, secretory organs, bark rays, while the primary bark parts, often having disappeared, could only serve as distinguishing features for a limited number of barks.
If the number of bark parts considered were to be further enlarged the use of a x 20 lens might become necessary.