Cm Of Stem Research Articles

Starch and hexoses concentrations as physiological markers in dormancy progression of sweet cherry twigs

KEY MESSAGE: High starch concentrations in woody tissue of sweet cherry trees were associated with deep stages of dormancy, while increasing concentrations of hexoses were related to the dormancy release process. Dormancy is an intrinsic characteristic of deciduous forest and fruit trees. Release from dormancy and subsequent bud burst occur after chill requirements (CR) have been met. Currently, chilling metrics are poorly interchangeable among climates, probably due to a lack of physiological parameters involved in earlier model development, and, therefore, the reported CR values differ across locations. Here, we propose a way to improve our understanding on physiological markers involved in dormancy of deciduous fruit trees studying the dynamics of starch and hexoses (glucose + fructose) in sweet cherry twigs. Probabilities of bud break were estimated through logistic regression analysis using as independent variable the concentration of carbohydrates. In this experiment, we used 960 twigs and 160 sub-samples of twig portions (~ 2 cm of stem) from 8 sweet cherry cultivars exposed to different amounts of chill in the field. The timing of bud burst in forcing conditions and the concentration of starch and hexoses in the sub-samples were recorded. We found that concentrations of starch and hexoses are closely related to dormancy progression. Specifically, starch concentrations decreased by 43%, while concentrations of hexoses increased by 58% during the transition from 16 to 70 Chill Portions. Responses differed among varieties at the same chill received in the orchard. The logistic regression analysis revealed that the predicted probability of bud break at the moment of recorded bud burst was highest (i.e., up to 0.5) in the varieties Santina, Skeena, Rainier, Lapins, Regina, Kordia and Bing. In contrast, the variety Sweetheart showed the lowest probability (i.e., 0.49) of having met its CR when bud burst was recorded. This may suggest that in this variety, carbohydrate metabolism is not the most important predictor involved in dormancy release. The method presented here improves our understanding on dormancy and might serve to focus further research on dormancy modeling. This is especially important in warm winter regions where the classical way of determining CRs and quantifying chill accumulation is consistently failing.

SUBSTRATOS E AUXINAS NO ENRAIZAMENTO DE ESTACAS CAULINARES DE ESPINHEIRA-SANTA

A espinheira-santa (Maytenus ilicifolia) é uma planta medicinal cujas folhas são utilizadas no tratamento de úlceras gástricas, mas apesar de sua importância, são poucas as informações publicadas sobre a produção de mudas e técnicas de propagação vegetativa da espécie. Este trabalho teve por objetivo avaliar o enraizamento de estacas caulinares de espinheira-santa submetidas à aplicação de duas auxinas, em dois substratos. Estacas caulinares semilenhosas foram preparadas com uma folha e 1 cm de caule, e caulinares herbáceas com duas folhas e 6 a 8 cm de comprimento. Estacas semilenhosas foram tratadas com ácido naftaleno acético (ANA 0, 1500, 3000 mg L-1) e herbáceas com ácido indolbutírico (AIB 0, 250, 500 e 1000 mg L-1), em solução, e plantadas em tubetes contendo vermiculita ou fibra de casca de coco, sendo mantidas em casa-de-vegetação. Para estacas semilenhosas observou-se maior porcentagem de enraizamento na testemunha (12,50% e 6,25%), número médio de raízes por estaca de 1,48 e 1,04 e comprimento médio de raízes de 1,28 e 2,03 cm para a testemunha, em vermiculita e fibra de casca de coco, respectivamente. Para estacas herbáceas obteve-se 16,00% de enraizamento, 2,46 raízes por estaca e comprimento médio de raízes de 0,89 cm para a testemunha, em vermiculita. Não houve enraizamento em fibra de casca de coco. Verificou-se maiores porcentagens de sobrevivência e menores porcentagens de mortalidade em estacas semilenhosas, enquanto que em estacas herbáceas observou-se o inverso. Estacas caulinares semilenhosas e herbáceas de espinheira-santa não respondem à aplicação ANA e AIB.

Assessment of the frost hardiness of shoots of silver birch (Betula pendula) seedlings with and without controlled exposure to freezing

Frost hardiness (FH) of the shoots of silver birch (Betula pendula Roth) container seedlings was assessed by electrolyte leakage (EL), visual scoring of damage to the stem (SB), and whole-plant viability tests after controlled exposure to freezing during frost hardening. FH was calculated as the temperature causing a 50% or 10% increase in electrolyte leakage (ELT50, ELT10), stem browning (SBT50, SBT10), proportion of damaged seedlings (DT50, DT10) or mortality (LT50, LT10). Heterogeneous variances in error are considered in the estimation of the above indices by nonlinear regression of the logistic function. A method for computing the standard error of the estimated temperature causing 10% damage is described. The FH estimates by the most reliable method of assessment SBT50 were then compared with electrical impedance parameters (EIS) and water contents (WC) measured without controlled exposure to freezing. Comparison of FH assessment methods showed that ELT50 estimated the DT10, SBT50, and DT50 well. The WC of the uppermost 10 cm of stem decreased in early autumn, when FH was above –10 °C. When the rapid increase in FH started, WC stabilized. Intracellular and extracellular resistance measured by EIS of unexposed stems correlated positively with FH.

Mutagenic Effects of Acute Gamma Irradiation on Miniature Roses: Target Theory Approach

Absorbed gamma-ray doses of 50, 100, and 200 Gy were used to produce mutations in miniature rose (Rosa hybrida) bushes of `Blue Blood' (BB), `Mountie' (MT), `Dark Red Mountie' (DM), and `Potluck' (PL) cultivars. The fairly good agreement achieved between measured and calculated doses from the extended gamma-ray source provided a high degree of confidence in reporting these doses. The relationship between plant height reduction (H) and absorbed dose (D) could be described as H = A - BD + CD2, in accordance with the prediction of the multi-hit target theory, where A, B, and C are constants. The mean spine number per 10 cm of stem, the mean petiole length, and the mean petal number were significantly (P≤0.05 to 0.001) reduced in all cultivars depending on D. The total number of mutations was highest in PL. The irradiated plants remained fertile. The range in color increased substantially for all the cultivars. The number of flowers in an inflorescence decreased for PL, BB, and DM but not for MT.

Systemic acquired silencing: transgene-specific post-transcriptional silencing is transmitted by grafting from silenced stocks to non-silenced scions.

Using grafting procedures, we investigated the transmission of co-suppression of nitrate reductase and nitrite reductase host genes and transgenes and of post-transcriptional silencing of a uidA transgene encoding glucuronidase in tobacco. We demonstrate that silencing is transmitted with 100% efficiency from silenced stocks to non-silenced scions expressing the corresponding transgene. Transmission is unidirectional from stock to scion, transgene specific, locus independent and requires the presence of a transcriptionally active transgene in the target scion. The transmission of co-suppression occurs when silenced stocks and non-silenced target scions are physically separated by up to 30 cm of stem of a non-target wild-type plant. Taken together, these results suggest that a non-metabolic, transgene-specific, diffusable messenger mediates the propagation of de novo post-transcriptional silencing through the plant.

Blueberry Flower-bud Hardiness Is Not Estimated by Differential Thermal Analysis

Differential thermal analysis (DTA) was used to study the freezing behavior of `Berkeley' blueberry (Vaccinium corymbosum L.) flower buds at cooling rates of 10, 5, and 2C/hour. Experiments were conducted at various stages of hardiness on excised and attached (5 cm of stem) buds. The presence and number of low-temperature exotherms (LTEs) in hardy buds generally increased when analyses were conducted using faster cooling rates with excised buds. The number of LTEs detected in individual buds did not correlate (r2 = 0.27) with the number of injured florets. The inability to detect LTEs in buds attached to stem segments and cooled at 2C/hour indicates that DTA cannot reliably estimate blueberry flower-bud hardiness in field plantings.

BORON AFFECTS LOWBUSH BLUEBERRY FRUIT SET AND YIELD

Five lowbush blueberry (Vaccinium Angustifolium Ait.) clones with leaf tissue boron levels below 20 ppm were selected in a commercial lowbush blueberry field in Washington County, Maine. Four 2.4 M2 treatment plots established on each clone received a foliar spray of Solubor at 0, 200, 400 or 600 ppm boron in September. The terminal 3.8 cm of stem, sampled in November, had increased concentrations of boron with increasing rates of boron application. Boron sprays also increased boron leaf tissue concentrations in July of the crop year. Ten stems with four flower buds were tagged in each treatment plot to determine the effect of boron treatments on fruit set and berry size. Fruit set was the same for each bud, but the number of blossoms and fruit per bud was greater on buds below the terminal. Yield increased in response to boron application up to 400 ppm, due to increases in fruit set, berry number and berry size of three of the five clones.

Cryosophila macrocarpa (Palmae), a New Species from Chocó Department, Colombia

Cryosophila macrocarpa (Palmae), a New Species from Chocó Department, Colombia

Transport of Rb and Sr to the ear in mature, excised shoots of wheat: Effects of temperature and stem length on Rb removal from the xylem

Wheat (Triticum aestivum L. cv. ‘Arina’) shoots grown in the field were excised post-anthesis and incubated in the laboratory for 72 h standing in 2 mM RbCl+2 mM SrCl2. Strontium is a phloemimmobile, xylem-mobile element and indicates the distribution of the xylem sap in the plant. Rubidium is easily transported in the phloem and behaves similarly to the highly mobile K as far as the redistribution within the plant is concerned, although Rb cannot substitute physiologically or biochemically for K. The Sr contents in the ear were hardly affected by stem length or by steam-girdling (phloem-interruption). Rubidium on the other hand accumulated in the stem. A peduncle length of 5 cm was sufficient to decrease the Rb concentration in the xylem by more than 50% at 25°C. Only a minor quantity of Rb reached the ear after passing through 20 cm of stem without nodes and this transport was prevented by steam-girdling. A remarkable flux of Rb into the ear was observed in shoots with a vascular connection between the flag leaf lamina and the ear. Our results suggest that Sr was transported with the transpiration stream, while Rb was rapidly eliminated from the xylem and reached the ear via the phloem. The temperature optimum for the removal of Rb from the xylem was around 35°C. The nodes may further contribute, but are not prerequisites for this redistribution. The observed transfer processes could allow a solute specific transport via the xylem and phloem of maturing cereals and may be an important factor influencing the nutrient economy in the field.

Plant part selection and evaluation of factors affecting analysis and recovery of nitrate in irrigated durum wheat tissue

Abstract Periodic nitrate tissue tests are used to determine nitrogen (N) fertility status of a variety of crops. Data on the importance of plant part selection, sample handling techniques, grinding criteria and extraction conditions in N03‐N analysis of wheat tissue are essential if the procedure is to achieve widespread adoption and use. Detailed partitioning of field grown durum spring wheat (Triticum durum) plants at the Feekes 2 (3–4 leaf), 6 (joint) and 10 (boot) growth stages was conducted to document which plant part exhibits the greatest accumulation of NO3‐N. Sample handling, fineness of tissue grinding, different tissue: extractant ratios and extraction times were examined to determine their effects on NO3‐N recovery. Partitioning data confirmed previous findings which identified the basal stem between ground level and the seed prior to jointing and the 5 cm of stem just above ground level thereafter as the plant parts showing the greatest accumulation of NO3‐N. Therefore, these plant parts hav...

Measurement of Unloading and Reloading of Photo-assimilate within the Stem of Bean

Minchin, P. E. H. and Thorpe, M. R. 1987. Measurement of unloading and reloading of photo assimilate within the stem of bean.—J. exp. Bot. 38: 211-220. There is growing evidence that the phloem transport pathway is leaky with passive unloading into the apoplast and active reloading from the apoplast. In this paper we report in vivo measurements of unloading and reloading in immature stems of bean expressed as a percentage per unit length of the photo-assimilate flow within the transport pathway. Gross unloading was up to 6% cm-1 and net unloading up to 4% cm-1. Time constants of bulk flow through 10 cm of stem were about 4-6 min whereas those of net unloading were 8-13 min and of gross unloading, at the most, 7-8 min.

Stem Anoxia Temporarily Interrupts Translocation of 11C-Photosynthate in Sunflower

Treatment of 5-0 cm of stem or petiole of sunflower with nitrogen gas for 5 min or longer reduced phloem translocation of nC-photosynthate or stopped it entirely for a 15-20 min period after which time it slowly resumed. When the N2 was replaced by air the transport restarted immediately and soon reached speeds higher than pre-anoxia rates. Thus anoxia, which we know inhibits export of photosynthate by preventing dark respiration in the leaf (Grodzinski, Jahnke, and Thompson, 1984), also inhibited transport in veins. It reduced the speed of photosynthate movement eventually stopping it, probably by inhibiting the loading-unloading mechanisms along the sieve-tubes. These mechanisms are, apparently, themselves under control of a metabolic respiratory mechanism (Fensom, 1981). Short-term anoxia of the stem did not appreciably affect the loading and transport in the leaf; it probably did not destroy the integrity of membranes at the point of treatment nor cause a physical blockage of sieve-plate pores nor change the viscosity of sieve-tube sap. A metabolic component which assists transport is indicated in the mechanism of short-term translocation in sunflower.

Cytokinesis, Cell Expansion, and the Potential for Cytokinin-Autonomous Growth in Tobacco Pith

Pith tissue from Nicotiana tabacum L. cv ;Maryland Mammoth' or ;Wisconsin 38' was isolated, free of vascular tissue, and cultured on a medium containing auxin but no cytokinin. Explants from the apical 1 cm of stem, within the pith rib meristem, initiated callus growth with 100% efficiency. Macroscopically visible callus was evident 5 days after the tissue was isolated, and the cultures grew persistently in the absence of cytokinin. Heat treatment, sometimes used to initiate cytokinin habituation, was not required. Explants from tissue basipetal to the pith rib meristem declined in the frequency of habituation with increasing distance from the shoot apex. Although pith tissue which was growing, in vivo, was more prone than mature tissue to establish cytokinin-habituated callus, the basipetal decline in habituation frequency extended well beyond the zone of cell expansion. Explants from mature pith 40 centimeters or more from the shoot apex grew in the absence of cytokinin with 18% frequency, although the response required at least 2 weeks of culture. Further analysis demonstrated that tissue near the periphery of mature pith was more prone to cytokinin-habituation than tissue from the pith center.

Pulse Treatment with Silver Nitrate Extends Vase Life of Anthuriums1

Abstract Short pretreatments of stems of anthurium flowers (Anthurium andraeanum André) with silver nitrate solutions increased vase life by 40 to 60% after a simulated shipping. Significant improvement was obtained with a single 10-minute treatment with 1 mm silver nitrate. Maximum postharvest life was obtained with flowers treated with silver nitrate within 12 hours of harvest. Silver nitrate treatment was effective on flowers ranging from half to full maturity. No measurable silver was translocated to the spathe or spadix. Silver thiosulfate complex was not as effective as silver nitrate. For response to silver treatment following simulated shipping of 3 days, 2 cm of stem had to be removed before placing in a vase solution. Continuous maintenance of the flower before and after simulated shipping in a commercial preservative was not significantly better than a single pulse with silver nitrate or a combination of silver nitrate pulse and commercial preservative.

Yield and growth responses of kenaf (Hibiscus cannabinus L.) in a semi-arid tropical environment to irrigation regimes based on leaf water potential

The growth response of kenaf (Hibiscus cannabinus L.) to four irrigation schedules based on leaf water potential Χl was evaluated in a semi-arid tropical environment. Total dry matter production was unaffected by regimes in which the mean value of leaf water potential Χl (mean of solar noon and dawn value) did not fall below −1.26 MPa. Stem elongation was more sensitive than dry matter accumulation to plant water stress. — The economic yield for paper pulp production (i. e. total plant dry matter production minus that of the foliage and upper 60 cm of stem) increased with the frequency of irrigation. — Growth recovery by kenaf following a period of water stress was examined. Alleviation of water stress 10 weeks after irrigation, when Χl was −1.60 MPa, produced stem elongation rates that were greater than those of plants previously receiving irrigation. This ability to withstand water stress and partially compensate in growth following alleviation of the stress indicates that the kenaf crop has stress response features suitable for rainfall only production under semi-arid tropical conditions. — Irrigation schedules based on Χl resulted in water applications tailored to crop requirements in that water use increased, and the time interval between irrigation decreased, with increasing canopy development as well as with increasing evaporative demand. However, erratic fluctuations in Χl between irrigations make scheduling by this method difficult and the use of daily mean, dawn or noon values of Χl for scheduling irrigation of kenaf cannot be recommended in environments of high evaporative demand. The factors contributing to these fluctuations in (Χl) are discussed.