Hordeum vulgare cv. California Mariout was grown for 50 d in sand culture at 100 mol m-3 NaCl. Xylem sap was collected through incisions at the base of individual leaves along the stem axis by applying pressure to the root system. K+ concentrations in the xylem sap reaching individual leaves increased towards the apex, while concentrations of Na+, NO3-, and Cl- declined. Phloem exudate was obtained by collecting into Li2EDTA from the base of excised leaves. K/Na ratios of phloem exudates increased from older to younger leaves.K/Na ratios in xylem sap and phloem exudate were combined with changes in ion content between two harvests (38 and 45 d after germination) and the direction of phloem export from individual leaves, to construct an empirical model of K+ and Na+ net flows within the xylem and phloem of the whole plant. This model indicates that in old leaves, phloem export of K+ greatly exceeded xylem import. In contrast, Na+ export was small compared to import and Na+ once imported was retained within the leaf.The direction of export strongly depended on leaf age. Old, basal leaves preferentially supplied the root, and most of the K+ retranslocated to the roots was transferred to the xylem and subsequently became available to the shoot. Upper leaves exported to the apex. Young organs were supplied by xylem and phloem, with the xylem preferentially delivering Na+, and the phloem most of the K+. For the young ear, which was still covered by the sheath of the flag leaf, our calculation predicts phloem import of ions to such an extent that the surplus must have been removed by an outward flow in the xylem. Within the culm, indications for specific transfers of K+ and Na+ between xylem and phloem and release or absorption of these ions by the tissue were obtained.The sum of these processes in stem internodes and leaves led to a non-uniform distribution of Na+ and K+ within the shoot, Na+ being retained in old leaves and basal stem internodes, and K+ being available for growth and expansion of young tissues.

Journal Article Concentrations and Transport of Solutes in Xylem and Phloem along the Leaf Axis of NaCl-treated Hordeum vulgare Get access OLAF WOLF, OLAF WOLF 3 1CSIRO Division of Plant IndustryGPO Box 1600, Canberra ACT 2601, Australia2Lehrstuhl für Botanik IMittlerer Dallenbergweg 64, 8700 Würzburg, West Germany 3 To whom correspondence should be addressed at: Lehrstuhl fur Botanik I, Mittlerer Dallenbergweg 64, 8700 Wurzburg, West Germany. Search for other works by this author on: Oxford Academic PubMed Google Scholar RANA MUNNS, RANA MUNNS 1CSIRO Division of Plant IndustryGPO Box 1600, Canberra ACT 2601, Australia Search for other works by this author on: Oxford Academic PubMed Google Scholar M. LORRAINE TONNET, M. LORRAINE TONNET 1CSIRO Division of Plant IndustryGPO Box 1600, Canberra ACT 2601, Australia Search for other works by this author on: Oxford Academic PubMed Google Scholar W. DIETER JESCHKE W. DIETER JESCHKE 2Lehrstuhl für Botanik IMittlerer Dallenbergweg 64, 8700 Würzburg, West Germany Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Experimental Botany, Volume 41, Issue 9, September 1990, Pages 1133–1141, https://doi.org/10.1093/jxb/41.9.1133 Published: 01 September 1990 Article history Received: 10 January 1990 Published: 01 September 1990

Plants of barley (Hordeum vulgare cv. Clipper) were grown in solutions containing 0, 100 or 175 mol m-3 NaCl from leaf 3 emergence until anthesis. Na+ and Cl- concentrations in various growing tissues of the shoot were measured concurrently with increases in dry weight. The tissues on which the study focused were the basal 30 mm of leaves 4 and 7 (mainly expanding cells), and the primordial stage of leaf 7 and the floral apex (mainly dividing cells). Although leaf growth was reduced by the higher NaCl treatments, apex growth was initially increased. Na+ and Cl- concentrations were high in the expanding tissues (150 mol m-3), but there was no consistent relation between the concentrations and the growth rate. Na+ and particularly Cl- concentrations were much lower in the dividing tissues, and again did not correlate with the rate of development of the tissue, or the final size of the organ. These data strongly indicate that the growth of the shoot is not directly controlled by local concentrations of Na+ or Cl- of the growing tissues, but by some influence originating elsewhere in the plant.

Sieve tube sap was collected from fully expanded leaves of NaCl-treated barley plants through aphid stylets. The sap was analysed for Na+, CI-, K+, phosphate, sucrose and osmolality. Na+ and Cl- appeared in the sap within a day of NaCl being added to the nutrient solution. When plants were exposed to various NaCl concentrations for 1-2 weeks, the sap contained about 15 mol m-3 Na+ and 25 mol m-3 Cl+, irrespective of whether the external NaCl concentration was 25, 100 or 200 mol m-3. When plants were kept for more than 2 weeks at 200 mol m-3 NaCl, the Cl- concentration in the sap increased but the Na+ concentration remained the same. Na+ and Cl- in the sap decreased very slowly when NaCl was removed from the nutrient solution. The calculated efflux of Na+ and Cl- in the phloem from the leaves was only 10% of the influx in the xylem, so the phloem can play little part in controlling the NaCl content of the leaves of these plants.

Seed was collected from jojoba [Simmondsia chinensis (Link) Schneider] plants growing at three field sites in two years. The wax percentage was determined by nuclear magnetic resonance and the compositions of the wax and the ethanolysis products (one site only) were determined by gas chromatography. The mean wax concentration varied from 49.2 to 55.1% over all sites and years. The percentage of long-chain wax esters (>C40) decreased linearly with increase in mean maximum temperature during the period of linear seed growth (r = 0.93). The decrease in long-chain esters was associated with a decrease in the C22 and C24 fatty acids and alcohols. Data from controlled environment studies and from field studies were used to assess the effect of temperature on the percentage elongation, reduction and esterification of acyl-CoAs of carbon lengths 18-22. High temperature lowered the specificity for elongation of C20-C22 and of C22-C,24 and increased the specificity for reduction of the C20 acid to its corresponding alcohol. The amount of C42 wax ester was greater than would be expected by random association of the alkoxy-acyl groups but this preference was not as great at high temperatures.

Jojoba plants were grown in large pots in temperature-controlled phytotron glasshouses. The flowers were hand-pollinated and the seeds were grown under a range of eight temperature regimens from 15/10 to 36/31C (8/16 h; photoperiod 16 h). The concentration of wax in the seed was determined by nuclear magnetic resonance and the wax composition and the composition of the ethanolysis products of the wax were determined by gas chromatography. At 21/16C the wax concentration increased with seed growth until the seed reached 75% of its mature weight and then stabilized at about 45%. The wax concentration in mature seeds was only slightly affected by temperature, except for the extreme treatments of 15/10 and 36/31C where the concentration was reduced. The main effect of temperature on wax composition was the depression of the percentage of waxes with carbon chain lengths greater than 40 at temperatures over 30/25C. This depression was associated with a reduction in the percentage of C22 and C24 fatty acids and alcohols. The effects of temperature will have to be taken into account by plant breeders selecting for high wax content or for a particular wax composition.

A method for the routine determination of jojoba wax ester composition and the ethanolysis products of these esters is described. In the recommended procedure, single or half seeds are crushed onto filter paper disks to provide duplicate 10–20 mg samples of the wax. One paper is extracted with petroleum ether for wax ester analysis and the second sample is transesterified in a sealed bottle using 5% HCl in ethanol at 80 C for 1–2 hr. This preparation is extracted with NaCl and petroleum ether, neutralized with potassium bicarbonate and dried with anhydrous sodium sulfate. The fatty acid ethyl esters and free alcohols are determined by gas chromatography (GC). The method requires only small amounts of seed material, provides duplicate samples of the wax, simplifies the ethanolysis procedures and reduces the time needed for the removal of the acid catalyst.

The soil and plant water status of irrigated and unirrigated sorghum [Sorghum bicolor (L.) Moench cv. TX610] and sunflower (Helianthus annuus L. cv. Hysun 30) crops were compared on several days from the late vegetative to the early grain-filling stages of development. Additionally, the stems of plants from the irrigated and unirrigated plots of both species were cut near their base; this caused the plants to quickly dry until the stomata closed. The leaf water potential and leaf osmotic potential were measured when the stomatal resistance reached 6 s cm- to give the water potential for stomatal closure and to provide osmotic potentials at equal turgor. Carbohydrate and potassium levels of leaves were also monitored. The mean daily minimum leaf water potentials in the irrigated sorghum and sunflower did not decrease below - 1 7 MPa and - 2.0 MPa, respectively, but decreased to - 2.1 MPa in the unirrigated sorghum and -2.6 MPa in the unirrigated sunflower. The osmotic potential at stomatal closure in the rapidly dried plants decreased with increasing leaf water deficit in both sunflower and sorghum: in both species the osmotic potential decreased approximately 0.6 MPa for each megapascal decrease in leaf water potential. The results indicate that both sorghum and sunflower adjusted osmotically in response to water deficits and that adjustment occurred at a rate of at least 0.1 MPa per day. The lowering of osmotic potential persisted less than 9 days after the relief of stress in both sunflower and sorghum. The soluble sugar concentration increased linearly in both sunflower and sorghum with osmotic adjustment: the rate of increase of soluble sugars was significantly greater in sunflower than sorghum. No changes in potassium concentration were observed during osmotic adjustment. The water potential at which the stomata closed varied from - 1.5 to -2.6 MPa in sorghum and - 1.7 to -2.7 MPa in sunflower: the water potential that induced stomatal closure decreased as the osmotic potential decreased. Stomatal closure occurred at a mean turgor of -0-5 MPa in both species: systematic error in the measurement of osmotic potential on frozen and thawed leaf tissue is considered the reason for the low turgor potentials at stomatal closure. The adaxial stomatal closed before the abaxial stomata in the sorghum and unirrigated sunflower but, since the leaf water potential initially fell rapidly and then became stable before the adaxial stomata closed, both the adaxial and abaxial stomata closed at the same leaf water potential.