Root Dry Weight Ratio Research Articles

Variation among Red and Freeman Maples in Response to Drought and Flooding

Freeman maples (Ace×freemanii E. Murray) are marketed as stress-resistant alternatives to red maples (Acer rubrum L.). Our objective was to compare two cultivars of Freeman maple [`Jeffersred' (Autumn Blaze®) and `Indian Summer'] and five red maples [`Franksred' (Red Sunset®), `Autumn Flame', `PNI 0268' (October Glory®), `Fairview Flame', and unnamed selection 59904] for effects of flooding and water deficit on plant growth, biomass partitioning, stomatal conductance, and leaf osmotic potential. Plants grown from rooted cuttings in containers were subjected to three consecutive cycles during which root-zone water content decreased to 0.12, 0.08, and 0.02 m3·m–3, respectively. Additional plants were flooded for 75 days, while plants in a control treatment were irrigated frequently. Stomatal conductance immediately before imposing drought and after three drought cycles did not differ among genotypes and averaged 220 and 26 mmol·s–1·m–2, respectively. Differences in stomatal conductance after recovery from the first drought cycle and at the end of the second drought cycle did not vary with species. Drought reduced estimated leaf osmotic potential similarly for all genotypes; means for drought-stressed and control plants were –1.92 and –1.16 MPa, respectively. Freeman maples had a higher mean root: shoot weight ratio and a lower leaf surface area: root dryweight ratio than did red maples. Across genotypes, stomatal conductance of flooded plants initially increased by ≈20% and then fell to and remained below 50 mmol·s–1·m–2. Stomatal conductance of `Indian Summer' decreased to ≈20 mmol·s–1·m–2 after 8 days of flooding, indicating that this cultivar may be particularly sensitive to root-zone saturation.

Effects of NaCl salinity and CO 2 enrichment on pepino ( Solanum muricatum Ait.) : I. Growth and yield

One-month old, rooted, semi-hardwood cutting plants of pepino cv. Xotus in sand-potted culture were treated with 200 ml Hoagland nutrient solution with or without additional 25 mM NaCl twice a week for 2 months, and exposed to 350 ± 10, 700 ± 10 or 1050 ± 10 ppm CO 2 in controlled environment chambers during the last month of the experiment. NaCl salinity in the rhizosphere reduced growth of all the organs, but raised stem dry weight ratio and root dry weight ratio. In contrast, atmospheric CO 2 enrichment increased plant and fruit growth. Leaf dry weight ratio and fruit dry weight ratio rose, but stem dry weight ratio and root dry weight ratio decreased at high CO 2 levels. Daily expansion rate of leaf area, growth rate of side-shoot length, rate of plant dry mass production, and increased rate of fresh fruit weight decreased due to NaCl stress, but increased with CO 2 enrichment. Side-shoot diameter rose, whereas specific leaf area, leaf area ratio, and side-shoot dry weight ratio declined under both NaCl-stressed and CO 2-enriched conditions. In comparison with the 350 ppm CO 2 treatment without NaCl salinity in the rhizosphere, net assimilation rate and relative growth rate of plants were reduced by 8–13% and 16–32% due to NaCl salinity, and enhanced by 22–23% and 42–64% at 700 ppm CO 2, and by 36–44% and 64–101% at 1050 pm CO 2, respectively. The simultaneous treatments of NaCl salinity and high CO 2 resulted in indefinite effects on vegetative and reproductive growth as well as on dry mass production of different plant organs. Nevertheless, the negative impacts of NaCl stress on plant growth and fruit yield diminished at high CO 2 levels. Atmospheric CO 2 enrichment increased the tolerance of pepino to NaCl salinity in the root medium.

Comparative ecology of Monochoria korsakowii and M. vaginalis

Two native annual species, Monochoria korsakowiiRegel et Maack and M. vaginalis (Burm. fil.) Kunth, occur in Japan. Although they show similar habitat preferences, these plants are now in contrasting situations in Japan; while M. vaginalis is a noxious weed, M. korsakowii, a once common weed of rice fields, has diminished its distributional range and is now listed as a vulnerable species. For the purpose of conservation and management of M. korsakowii, the life history traits of these species were investigated with particular emphasis on the seasonal growth cycles, patterns of dry matter distribution and photosynthetic and transpiration rates. We found significant differences in phenology and seasonal growth between M. korsakowii and M. vaginalis. M. korsakowii germinated about a month earlier and flowered one and a half months later than M. vaginalis. While shoot to root dry weight ratio in M. korsakowii was larger than 1.0, that in M. vaginalis was smaller than 1.0 during growth. Differences were also found in leaf life span, numbers of leaves and flowers per individual plant and transpiration rate. These findings support the belief that the decline of M. korsakowii relates, to some extent, to the recent changes in agricultural practices in Japan.

Phenotypic plasticity of Ammannia spp. in competition with rice

SummaryThe annual broadleaved weeds Ammannia auriculata Wild, and A. coccinea Rottb. are widespread and competitive in California rice (Oryza sativa L.) fields. We studied Ammannia spp. biology in a greenhouse pot experiment. Weeds were grown alone and in competition with rice (cv. M–202), and harvested six times over 122 days. Compared with growth alone, competition reduced Ammannia spp. total plant dry weight (DW), shoot DW and leaf area in all but the first harvest. However, weed height differed at only one harvest (85 days after planting). Ammannia spp. responded to competition with increased shoot:root DW ratios, increased stem:other shoot DW ratios, decreased stem diameters, fewer but elongated internodes and fewer branches. This suggests that light capture was more important than nutrient capture for maintaining Ammannia spp. growth. The weeds appear to lodge easily in rice fields because competitive growth responses make them top heavy and unstable. Weed seed DW declined by 97% in competition, which showed the importance of crop interference to Ammannia spp. control. Plasticity may help Ammannia spp. to escape common control practices (e.g. high crop plant densities or early herbicide application), and probably contributes to its widespread distribution. Thus, Ammannia spp. plasticity should be more fully considered when designing management strategies.

The effects of external magnesium concentration on the growth and magnesium inflow rates of micropropagated cherry rootstocks 'F.12/1' (Prunus avium L.) and 'Colt' (Prunus avium L. × Prunus pseudocerasus L.)

The cherry rootstock 'F.12/1' is more susceptible to Mg deficiency than the cherry rootstock 'Colt'. The effects of different external concentrations (3000, 500, 50 and 10 µM) of Mg on the growth of micropropagated plants of 'F.12/1' and 'Colt' were investigated in a flowing solution culture system. The relative growth rates (RGR) and total dry weight of both cultivars decreased similarly with the reduction in the external concentrations of Mg. The decreases were caused by a lower net assimilation rate (unit leaf rate). 'F.12/1' had a greater RGR than 'Colt' at all external concentrations of Mg and this is ascribed to its greater leaf weight ratio (leafiness). 'Colt' partitions more dry matter to roots than 'F.12/1', resulting in a smaller shoot: root dry weight ratio. 'F.12/1' required a greater inflow rate of Mg than 'Colt' to maintain its maximum growth rate. When the external concentration of Mg fell below 500 µM the concentration of Mg in the leaves of 'F.12/1' fell well below the critical concentration whereas for 'Colt' this did not occur until the concentration fell below 50 µM.

Varietal differences in perennial ryegrass for nitrogen use efficiency in leaf growth following defoliation: performance in flowing solution culture and its relationship to yield under simulated grazing in the field

Varietal differences in rates of NO3 uptake and remobilization of nitrogen (N) during a cycle of severe defoliation and regrowth were assessed in perennial ryegrass (Lolium perenne L.) varieties Ba11778, Aberelan, Talbot and Gator. Plants were grown in flowing solution culture for 34 days, prior to a 30 d treatment period, including 21 d of regrowth. Net uptake of NO3 was measured continuously from solutions maintained automatically at 10 mmol m-3NO3.15 N-labelled NO3 3 was supplied to the plants in situ for either 21 h immediately prior to defoliation, or for 7-11 days afterwards, to measure remobilization of N from roots and stubble into the regrowing leaves. The four varieties differed only slightly in total dry matter production over 30 d, but varied substantially in post-defoliation specific growth rate by the leaf fraction. Gator was the lowest ( 0.11 g g-1 d-1), Ba11778 the highest ( 0.15 g g-1 d-1) and Aberelan and Talbot intermediate in leaf regrowth rate. Varieties did not vary significantly in shoot: root dry weight ratio, but the rate of NO3 uptake per unit of leaf fresh weight during regrowth was 27% lower in Ba11778 than in Gator. Leaves of Ba11778 and Aberelan had a lower organic N concentration in the dry matter at the end of the regrowth period than Talbot, which, in turn, had a lower concentration than Gator. Varieties differed in amount of leaf dry matter produced per unit of N absorbed by the plants after defoliation, the values (g g-1 N) being Ba11778 (22.6 ), Aberelan (20.7), Talbot (18.3) and Gator (16.7). More N was remobilized from the roots than from the stubble after defoliation. There were no significant differences among varieties in the amount and rate of N remobilization following defoliation. In earlier field experiments employing frequent cutting to simulate grazing, Ba11778 and Aberelan yielded at least 10% more dry matter annually than Talbot which, in turn, outyielded the amenity variety Gator by a similar amount. Thus the present results are consistent with the hypothesis that the efficiency of N use in leaf growth is an important factor determining genetic variation in productivity under frequent defoliation in the field when the herbage produced consists primarily of leaf.

Growth and partitioning of C and fixed N in the shrub legumeAcacia littoreain the presence or absence of the root hemiparasiteOlax phyllanthi

Nodulated plants of Acacia littorea were pot cultured singly in minus nitrogen sand culture in the presence or absence of a transplanted seedling of the root hemiparasite Olax phyllanthi and harvests of cultures made 4 and 8 months after introducing the parasite. Parasitism decreased host shoot growth while increasing root growth to a similar extent. Final shoot:root dry weight ratio was 2.2 for parasitized versus 4.3 for unparasitized Acacia. Partitioning of fixed N showed 4-fold larger N increments in shoots than roots of unparasitized plants, whereas parasitized plants lost a small amount of shoot N, made a root gain of N double that of unparasitized plants and lost over half of their N to Olax. The increment of fixed N in the host:parasite association was similar to that of unparasitized Acacia. Data on dry matter gain per unit foliage area and mean CO 2 assimilation rates per shoot of Olax and Acacia (parasitized or unparasitized) were discussed in relation to an estimated heterotrophic gain of xylem C from the host equivalent to 40% of the increment of dry matter C made by the parasite. Growth of Olax was accompanied by large increases in numbers of haustoria, 9% of which were attached to root nodules as opposed to roots. Structural and nutritional features of direct parasitism of nodules are described. Models of flow and utilization of C and N in the Acacia : Olax association and unparasitized Acacia are discussed in relation to published data for other host:parasite associations.

Fertilizer, Irrigation and Root Ball Slicing Affects Burford Holly Growth after Planting

Abstract Dwarf burford holly (Ilex cornuta ‘Burfordii Nana’) fertilized with 22.1 g N/container/yr of nitrogen during production in the nursery generated more new shoot weight but less root weight after transplanting to a landscape than those receiving 14.8 g N/container/yr. Slicing the root ball at planting, compared to not slicing, resulted in comparable regenerated root weight but reduced new shoot number, new shoot dry weight and new shoot:regenerated root dry weight ratio when irrigation was not applied daily after transplanting. Although irrigation frequency did not impact total weight of regenerated roots into landscape soil, more roots grew from the bottom half of the root ball when plants were irrigated periodically after planting than when plants received daily irrigation. Plants irrigated other than daily produced fewer shoots and less shoot weight than those receiving irrigation daily after transplanting. When plants were without irrigation for 4 or 6 days in the first week after transplanting, those planted without the nursery container on the root ball were more stressed (more negative xylem potential) than those planted with the container still on the root ball. However, two weeks later, plants without the nursery container were less stressed due to root growth into landscape soil.

Relationships Between Fire Response, Morphology, Root Anatomy and Starch Distribution in South-west Australian Epacridaceae

Selected epacrids (92 species in 15 genera) were examined with respect to fire response type, morphology, root anatomy and starch storage. Seeders, 75% of the species investigated, possessed a single main stem and a small root system with lateral roots which in most cases did not spread beyond the shoot canopy. Resprouter species were generally multi-stemmed with large lignotuberous root stocks. Certain seeder and resprouter species were intermediate in form and showed small root systems and basally branched main stems. Amounts of starch in roots of seeders (1.9±0.5mg starch gd.wt per root) were much less than in resprouters (14.1±3.3) whereas amounts in shoots were similar (1.9±0.5 and 1.6±0.6mg starch gd.wt per shoot, respectively). Starch storage in roots was mostly confined to rays of xylem parenchyma and inter-ray xylem parenchyma and the greater storage capacity of resprouters was generally due to broader rays. Growth zones in root xylem ranged from clear, verifiable annual rings, as in many seeder species, to indistinct growth zones, typical of many resprouter species. Shoot:root dry weight ratios were higher in seeders than resprouters. The study suggests that speciation within the Epacridaceae into seeder and resprouter forms involved divergent differentiation in terms of morphology, shoot:root dry weight ratio root storage of starch.

Enhancement of cadmium effects on growth and nutrient composition of birch (Betula pendula) by buthionine sulphoximine (BSO)

Binding of Cd to non-specific metal-binding peptides (phytochelatins) in birch roots has been suggested as an explanation for tolerance to Cd toxicity in birch (Betula pendula). In the present study, the tolerance of birch roots to Cd was further investigated by using buthionine sulphoximine (BSO) as an inhibitor of phytochelatin synthesis. Birch seedlings, grown in nutrient solution at pH 4.2, were exposed to 0 or 2 μM CdCl 2 combined with 0 or 0.1 mM BSO for 6 d. Plant growth (fresh weight increase and shoot to root dry weight ratio) and the nutrient composition in fine roots, whole roots and shoots were determined. The effects of Cd on growth confirms the results of earlier studies on birch, suggesting a reduced shoot growth, but preserved or stimulated root growth. When Cd and BSO were combined, overall plant growth was severely reduced. BSO was also shown to aggravate Cd-induced reductions of root and shoot concentrations of K, Ca and Mg but to impede the accumulation of Cd. The results suggest that phytochelatins participate in protecting the root against Cd interferences with growth, possibly by restricting Cd-induced changes in the nutrient composition of the plant.

Stem elongation and growth of Solanum tuberosum L. in vitro in response to photosynthetic photon flux, photoperiod and difference in photoperiod and dark period temperatures

Stem elongation and growth of potato plantlets under three DIF (difference in photoperiod and dark period temperatures) levels, −9, 0 and +9, combined with two PPF (photosynthetic photon flux) levels, 70 (low) and 140 (high) μmol m −2 s −1 provided by white cool fluorescent lamps, under 16 h day −1 (long) or 8 h day −1 (short) photoperiods, were studied. Four nodal cuttings were cultured for 21 days on 0.6 × 10 −4 m 3 MS (Murashige and Skoog, 1962, Physiol. Plant., 15: 473–497) agar (8 kg m −3) medium with no added sugar in 3.7 × 10 −3 m 3 polycarbonate boxes. Each box had two 10 mm holes covered with microporous filter to facilitate air exchange (3.6 air exchanges per hour). The average daily temperature in the culture room was set the same at 23 °C for all treatments, and CO 2 concentration and relative humidity were maintained at 400–500 μmol mol −1 and 50–70%, respectively. Stem length was significantly suppressed under 0 or −9 DIF, high PPF and long photoperiod. Stem diameter, leaf area and number of leaves were significantly enhanced by long photoperiod and high PPF, but affected little by DIF level. Specific leaf area was little affected by photoperiod, but decreased under high PPF and under low DIF. Long photoperiod and high PPF led to an increase in the fresh and dry weights maintaining similar percentage dry matter and to enhanced root growth. Under the same amount of integrated PPF, fresh and dry weights of leaf, stem, root and whole plantlet were significantly higher under the long photoperiod and low PPF conditions than under the short photoperiod and high PPF conditions. Because of suppressed root growth under short photoperiod, shoot to root dry weight ratio increased under short photoperiod, but was not affected by DIF. It is suggested that under photoautotrophic conditions a combination of high PPF level, long photoperiod, and zero or negative DIF produces potato plantlets in vitro of short and thick stem with similar number and increased area of leaves, which are desirable for transfer to ex vitro conditions.

A comparison of the dynamics of root growth and biomass partitioning in wild oat (Avena fatua L.) and spring wheat

SummaryThe dynamics of early root growth and dry matter partitioning were compared in spring wheat (Triticum aestivum L.) and wild oat (Avena fatua L.) grown in solution culture. Total root length was greater in wheat than wild oat throughout the experiment; a result of a greater number of seminal axes and greater production of lateral root length per axis. The final number of adventitious roots was greater in wheat than in wild oat, but their length was similar. Relative growth rates were also similar as was shoot:root dry weight ratio and rate of root respiration. However, wheat used the dry matter partitioned to its roots more efficiently, producing a greater specific root length (SRL, length per unit weight). Caution must be exercised when relating these results to plants growing and compet‐ing in the field, but three general points are raised. First, the initial number of seminal axes can have a profound effect on the rate of early root development; second, the adventitious root system of wild oat is not inherently more vigorous than that of wheat; and third, future studies should compare SRL of wheat and wild oat in the field. If differences similar to those in the present study are found they may contribute to the greater competitive ability of wheat.

Growth response of cotton to CO2 enrichment in differing light environments

Experiments were conducted to examine the growth responses of cotton (Gossypium hirsutum L. cv. Coker 315) to CO2 enrichment under different light regimes. Plants were exposed to 350 or 700 μl l−1 CO2 and six light treatments differing in photosynthetic period length (8 or 16 h) and in photosynthetic photon flux density (PPFD) for 32 days of vegetative growth. Higher PPFD (1 100 μmol m−2 s−1) was provided by a combination of high intensity discharge and incandescent lamps (HID), and lower PPFD (550 μmol m−2 s−1) was provided by fluorescent and incandescent lamps (F) or HID and incandescent lamps with shade cloth (HIDs). Growth was generally much slower with the 8‐h photosynthetic periods, but the growth stimulation by CO2 enrichment was larger than with 16‐h photosynthetic periods. After 28 to 32 days of treatment, the growth enhancement with CO2 enrichment was 152 and 78% for 8‐ and 16‐h photosynthetic periods, respectively, under HID; 100 and 77% in F, and 77 and 56% in HIDs. The higher PPFD of HID positively influenced the CO2 effect only at the slower growth rate in the 8‐h light period. The stimulation of leaf area expansion by CO2 enrichment was also greater with the 8‐h photosynthetic period for all light sources. These results, and others on net assimilation rate, shoot to root dry weight ratios and specific leaf weights, suggest that the growth response to CO2 enrichment with the longer photosynthetic period was depressed by limiting factors, perhaps nutritional, in the growth environment. The results also show that extensive variability in CO2 response can occur under light intensities which are often used in growth chamber experiments.

Analysis of Dry Matter Partitioning in Dactylis glomerata during Vegetative Growth Using a Carbon Budget Model

The dry matter partitioning in vegetative plants of Dactylis glomerata was studied from experiments performed in controlled environments. Plants were grown hydroponically in growth chambers, at two constant temperatures (17 and 25 °C). In both experiments the root fraction decreased regularly with time, an effect that was more accentuated in the higher temperature regime. In order to explain the change in dry matter partitioning, the experimental shoot and root growth were analysed using a carbon budget model which includes shoot and root maintenance requirements. The model predicts a relationship between the root specific growth rate and the product of shoot specific growth rate and shoot to root dry weight ratio. In the range of experimental accuracy, this relationship was found to be linear at both temperatures, which should indicate that the partitioning coefficients and the root maintenance coefficient remained constant during vegetative growth. The effect of temperature on the value of these coefficients can be specified from a linear regression analysis. Between 17 and 25 °C, the root maintenance coefficient increased by about a factor of two, whereas the partitioning coefficients did not vary significantly. On the basis of these results, it was shown that the decrease in root fraction during vegetative growth should be mainly attributed to the decrease in net specific activity of shoots.

The Significance of Root Starch in Post-fire Shoot Recovery of the Resprouter Stirlingia latifolia R. Br. (Proteaceae)

Stirlingia latifolia, a common shrub of Banksia woodlands of SW Australia, is a highly successful resprouter species recovering from fire by multiple sprouting of new shoots from its upper root stock. in comparison with the congeneric fire-sensitive (obligate seeder) species Stirlingia tenuifolia it exhibits a low shoot:root dry weight ratio and high concentrations of stored starch in the cortical tissue of its roots. The relationship between root reserves of starch and development of newly sprouting shoot material following fire is examined in S. latifolia after spring and summer burns. During the initial 2-5 month period after fire, levels of stored starch in the roots fall by 50-75%, followed by a slow increase as plants reproduce and the attainment of pre-fire starch levels by 1·5-2 years after the fire. Starch reserves of roots can be further reduced by shading the regenerating shoots to limit their input of photosynthates and almost totally eliminated by monthly removal of successive flushes of new shoots over a 10-12 month period. New shoots continue to sprout until all the starch is eliminated. The data are discussed in relation to the fire-induced reproduction of S. latifolia and its ability to thrive in very frequently burnt habitats.

Effects of Elevated Sucrose-Phosphate Synthase Activity on Photosynthesis, Assimilate Partitioning, and Growth in Tomato (Lycopersicon esculentum var UC82B).

The expression of a sucrose-phosphate synthase (SPS) gene from maize (Zea mays, a monocotyledon) in tomato (Lycopersicon esculentum, a dicotyledon) resulted in marked increases in extractable SPS activity in the light and the dark. Diurnal modulation of the native tomato SPS activity was found. However, when the maize enzyme was present the tomato leaf cells were unable to regulate its activation state. No detrimental effects were observed and total dry matter production was unchanged. However, carbon allocation within the plants was modified such that in shoots it increased, whereas in roots it decreased. There was, therefore, a change in the shoot:root dry weight ratio favoring the shoot. This was positively correlated with increased SPS activity in leaves. SPS was a major determinant of the amount of starch in leaves as well as sucrose. There was a strong positive correlation between the ratio of sucrose to starch and SPS activity in leaves. Therefore, SPS activity is a major determinant of the partitioning of photosynthetically fixed carbon in the leaf and in the whole plant. The photosynthetic rate in air was not significantly increased as a result of elevated leaf SPS activity. However, the light- and CO2-saturated rate of photosynthesis was increased by about 20% in leaves expressing high SPS. In addition, the temporary enhancement of the photosynthetic rate following brief exposures to low light was increased in the high SPS plants relative to controls. We conclude that the level of SPS in the leaves plays a pivotal role in carbon partitioning. Furthermore, high SPS levels have the potential to boost photosynthetic rates under favorable conditions.

Influence of Vesicular-Arbuscular Mycorrhizal Fungi on the Response of Potato to Phosphorus Deficiency.

Morphological and biochemical interactions between a vesicular-arbuscular mycorrhizal (VAM) fungus (Glomus fasciculatum [Thaxt. sensu Gerdemann] Gerdemann and Trappe) and potato (Solanum tuberosum L.) plants during the development of P deficiency were characterized. Nonmycorrhizal (NM) plants grown for 63 d with low abiotic P supply (0.5 mM) produced 34, 52, and 73% less root, shoot, and tuber dry matter, respectively, than plants grown with high P (2.5 mM). The total leaf area and the leaf area:plant dry weight ratio of low-P plants were substantially lower than those of high-P plants. Moreover, a lower shoot:root dry weight ratio and tuber:plant dry weight ratio in low-P plants than in high-P plants characterized a major effect of P deficiency stress on dry matter partitioning. In addition to a slower rate of growth, low-P plants accumulated nonreducing sugars and nitrate. Furthermore, root respiration and leaf nitrate reductase activity were lower in low-P plants than in high-P plants. Low abiotic P supply also induced physiological changes that contributed to the greater efficiency of P acquisition by low-P plants than by high-P plants. For example, allocation of dry matter and P to root growth was less restricted by P deficiency stress than to shoot and tuber growth. Also, the specific activities of root acid phosphatases and vanadate-sensitive microsomal ATPases were enhanced in P-deficient plants. The establishment of a VAM symbiosis by low-P plants was essential for efficient P acquisition, and a greater root infection level for P-stressed plants indicated increased compatibility to the VAM fungus. By 63 d after planting, low-P VAM plants had recovered 42% more of the available soil P than low-P NM plants. However, the VAM fungus only partially alleviated P deficiency stress and did not completely compensate for inadequate abiotic P supply. Although the specific activities of acid phosphatases and microsomal ATPases were only marginally influenced by VAM infection, VAM roots characteristically had a higher protein concentration and, consequently, enhanced microsomal ATPase and acid phosphatase activities on a fresh weight basis compared with NM roots. Morphological and ultrastructural details of VAM plants are discussed in relation to the influence of the VAM symbiosis on P nutrition of potato.

Genetic Variation in Chamaecyparis nootkatensis from Coastal British Columbia1

Abstract Genetic variation in several traits of Alaska-cedar (Chamaecyparis nootkatensis) was measured in progeny from seven coastal B.C. provenances, each represented by three open-pollinated families. The common-garden nursery trial also included one provenance of Port-Orford cedar (Chamaecyparis lawsoniana). Growth traits and frost hardiness were measured at the end of the first growing season, and morphological traits after the second year. Provenances varied in percentage germination, shoot dry weight, shoot to root dry weight ratio, number of lateral branches per stem, and cold injury to a minimum temperature of -20°C in December. Families differed in height, root collar diameter, and in the number of nodes of primary foliage. Port-Orford cedar exhibited much greater height, stem caliper, and dry weight than any Alaska-cedar provenance, but was more susceptible to frost damage. West. J. Appl. For. 7(1):25-29.

The Effect of Brushing on the Growth and Quality of Field-grown Root Crops

Shoots of field-grown plants of European radish (Raphanus sativus L. `Comet'), Japanese radish (daikon) (R. sativus L. `Mino-wase'), and Asian turnip (Brassica rapa L. `Hinona') were brushed twice daily, 40 cycles (back-and-forth strokes equal one cycle), for 8 (short-term) or 13, 21, or 14 days (long-term), respectively. European turnip (B. rapa L. `Hikari-kabu') plants were grown in a raised bed in an uncovered plastic house and were brushed for 9 or 21 days. Short-term brushing reduced root dry weight and the root: shoot dry weight ratio (R: S) of European radish, whereas the treatment increased these measurements for Asian turnip and European turnip. Short-term brushing had no effect on growth of Japanese radish plants, but increased root dry weight gain by both turnip cultivars, thereby increasing their R: S ratios. Lung-term brushing reduced root dry weight gain and the R: S ratio of European radish and root dry weight of Asian turnip but had no effect on these measurements for the other crops. Long-term brushing reduced cracking of European radish roots, thereby resulting in a higher proportion of oblong (medium quality) roots. Consequently, the percentage of marketable-quality roots of European radish was increased by brushing. Lung-term brushing increased the percentage of medium-sized roots of Asian turnip at the expense of large-sized roots. Brushing had no effect on root quality of European turnip.

Influence of root temperature on the potassium requirements of young tomato plants

The effect of low root temperature on the growth and K requirements of young tomato (Lycopersicon esculentum Mill. cv Sonatine) plants was investigated. When K was supplied in solution at high concentration (5 mM), lowering the temperature of the root system from 25° to 15°C reduced the relative growth rate so that after ten days plant dry weight was 60% and leaf area 44% of that of controls maintained at 25°C. Shoot: root dry weight ratio was initially increased by cooling, but declined to 84% of controls after ten days. In spite of these changes in shoot: root ratio the concentration of K in whole plants, expressed on the basis of tissue water, was stable throughout the experiment and was significantly higher than that of controls. Further, the critical concentration of K for shoots (the concentration in the shoot associated with 90% maximum growth) was also increased at root temperatures of 15° and 30°C compared with 24°C. It is suggested that the higher concentration of K at low root temperature may reflect a real increase in requirement for the element at the physiological level. Preliminary measurements of the solute potential demonstrated a less osmotically active sap in leaves of root-cooled plants, thus there may be a greater reliance on K as an osmoticum in these individuals. When supplies of K limited growth, root-cooling had no effect on any of the parameters determining the efficiency of its use; the minimum concentration to which roots could deplete the solution of K was identical for cooled and control plants and at the same stage of visible deficiency there was no significant difference in the efficiency ratio (mg DW, mg-1 K) or utilization efficiency (mg DW mM-1 K), in spite of large differences in the partitioning of dry matter.