Xylem and Phloem Import of Na+, K+, Rb+, Cs+ and Sb(SO4)2- in Tomato Fruits: Differential Contributions from Stem and Leaf

Wolterbeek, H. Th. and De Bruin, M. 1986. Xylem and phloem importof Na⁺, K⁺ , Rb⁺, Cs⁺ and in tomato fruits: differential contributions from stem and leaf.—J.exp. Bot. 37: 928–939. The transport of Na⁺, K⁺, Rb⁺, Cs⁺ and into developing fruits of tomato (an inbred lineof Lycopersicon esculentum Mill. cv. Tiny Tim) was measured.Element solutions were introduced into the transpiration streamthrough the cut stem bases of plant parts consisting of a stempart with single green fruit, both with and without attachedfully expanded leaf. Measurements were carried out of the accumulationin the fruit of the gamma-ray emitting radiotracers ²⁴Na⁺, ⁴²K⁺,⁸⁶Rb⁺, ¹³⁴Cs⁺ and The transport into the fruit was expressed by a single parameter taking intoaccount volume flows varying with time and experiments. Xylemto phloem transfer in the stem as a source of fruit elementsupply was shown to be inversely related with the velocity offlow of the stem xylem. The results also indicated that thetransfer system in the stem was more rapidly equilibrated thanit was in the leaf. Stem loading of the phloem is suggested as a possible mechanismregulating the solute influx in fruits under varying flow velocitiesof the stem xylem, while fruit influx of phloem solutes, whichwere loaded in the leaf, may play a major role in influx regulationunder conditions of varying solute concentrations. Key words: Alkali ions, tomato fruits, stem and leaf phloem loading     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability     

Some characteristics of monolayers of 1-palmitoyl-2-oleoyl-phosphatidylglycerol with and without dipalmitoylphosphatidylcholine during dynamic compression and expansion

Some properties of monolayers of $\text{1-}\text{palmitoyl}\text{-2-}\text{oleoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phospho}\text{-rac-}\text{glycerol}$ (POPG) alone or of POPG in mixtures with $\text{1,2-}\text{dipalmitoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phosphocholine}$ (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm²·s^?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m^?1 in the presence of Na⁺, Ca²⁺ or low pH (2.0) in the subphase. (3) The presence of Ca²⁺ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na⁺ or Ca²⁺ in the subphase.     

Peristaltic flow in tubes

The study is concerned with the analysis of two flow domains of peristaltic motion in tubes. In the first analysis the wall disturbance wavelength is much larger than the average tube radius. There is a simple algebraic relation between the average flow rate and pressure differential across a wavelength. In the second analysis the disturbance wavelength may be as small as the average radius. A numerical technique may be used to determine the relation between average flow rate and pressure differential across a wavelength.     

On the relationship between food, reproduction and survival of two carabid beetles: Calathus melanocephalus and Pterostichus versicolor

Abstract.

• 1 The relative influences of temperature and availability of food on reproduction, survival and growth of all developmental stages of two carabid beetle species are discussed with special reference to the suggested relationship between availability of food, size of egg production and survival of adults from one breeding season to the next.
• 2 Temperature as well as food supply influence the length of larval growth and adult body size. Beetles grown at low temperatures and low amounts of food are smaller than those grown at higher temperature and with more food.
• 3 The number of eggs laid per female was correlated with the amount of food gathered. There was no inverse relationship (trade-off) between reproductive output and survival in the field until the next breeding season.
• 4 In 1980 no significant relationship was found between winter mortality and the amounts of food gathered by beetles in the period after reproduction and before winter diapause. However, in 1981 in C. melanocephalus a lower number of starved beetles survived the winter than the fed ones and‘field’beetles.
• 5 Only in the first part of the feeding activity period in autumn can enough food be gathered by C.melunocephalus for successful hibernation. In the second part of this period there is not enough food to build up the fat reserves needed to survive the winter.
• 6 Difference in population fluctuations of both species are discussed in relation to their life histories.

     

8-Hydroxydeoxyguanosine in DNA from TPA-Stimulated Human Granulocytes

8-Hydroxydeoxyguanosine (8-OHdG) is now widely used as a sensitive marker of oxidative damage to DNA. When human granulocytes are stimulated with TPA, they release a large quantity of reactive oxygen species (superoxide, hydrogen peroxide) which might be expected to generate hydroxyl radicals (OH-) which in turn could produce 8-OHdG in the DNA. There had been considerable debate as to whether OH -is detectable in stimulated granulocytes; most workers now agree that none can be detected, unless exogenous iron is added. An earlier report had described that 8-OHdG (a marker of OH -) was increased in the DNA of TPA-stimulated, compared to control, granulocytes. We have repeated this experiment and have been unable to reproduce this Finding. We conclude that the amount of 8-OHdG produced in the DNA of TPA-stimulated human ganulocytes is indistinguishable from that seen in control (unstimulated) cells (less than one 8- OHdG/10⁵ dG).