Rootstocks.

Plants of many horticultural crops consist of multiple genetic systems, two or more distinct genotypes joined together as a single plant. The components are identified as the rootstock, interstem and scion. Grafting and budding are the processes that combine these components to establish vascular continuity between them to produce a single plant. Grafting may be natural or human initiated, forced grafting. This datasheet will mainly consider forced grafting with only a brief discussion of natural grafting. The rootstock is that component of the plant that fuses with the scion and provides the plants root system. Other terms used to describe this lower portion of the plant include stock and understock. Stock is synonymous with both rootstock and understock. Understock implies that the lower portion of the plant provides both the root system and some of the trunk while rootstock or stock implies that only the root system is provided by the lower piece. When grafting is performed high on the rootstock, the rootstock may also provide scaffold limbs. The scion is the plants shoot system. It is the component that produces the desired commodity in most cases, which are usually flowers or fruit. In perennials, the scion is nearly always vegetatively propagated. In grafted vegetables, the scion is usually propagated via seed. An interstem is a third genetic component of some grafted plants and is often selected to provide compatibility between the rootstock and the scion. Both grafting and budding combine dissimilar genotypes into one plant. Budding is a form of grafting where a single vegetative bud is used as the scion or interstem. Grafting refers to the condition where more than one bud on a common stem piece are combined with the rootstock or interstem. Perennial ornamental and fruit crops are the grafted crops that are familiar to most horticulturists. Annual vegetable crops are increasingly being grown as grafted plants and interest in using them in commercial production is rising steeply. Short lists of common rootstocks for a number of ornamental, fruit, nut and vegetable crops are presented in Tables 1-3 (at the bottom of this article). These lists are by no means complete, but provide an insight into the large number of rootstocks available in modern horticultural production. Specific recommendations for an area should be obtained from local experts. Good rootstocks should possess as many of the following crop appropriate characteristics as possible: affordable, long term graft compatible, easily propagated, promotes precocity and productivity, controls scion vigour, conveys pest resistance, improves stress tolerance, and has minimal suckering.

Estimation of Interstock and Intermediate Stock Usefulness for Summer Pear Cvs. Budded on Two Rootstocks

In order to increase the profitability of pear production, a greater density of weak growing trees per area unit should be planted. In Poland, the most frequently used pear dwarfing rootstocks are quince clones. The main disadvantage of them is a physiological incompatibility with some cultivars. The aim of this study was to evaluate the effect of the rootstock, interstock, and intermediate stock on growth and productivity of two summer pear cultivars, which are not compatible with the quince rootstock. Twoyear- old pear trees of ‘Radana’ and ‘Clapp’s Favourite’ cvs of different compositions were planted in the spring 2006. The following combinations were evaluated: ‘Radana’ and ‘Clapp’s Favourite’ on Caucasian pear seedlings, ‘Radana’ and ‘Clapp’s Favourite’ on quince SI with an intermediate stem piece of ’Doyenne du Comice’ and ‘Radana’ on Caucasian pear with ‘Pyrodwarf’ interstock. Up to the 6th year after planting, trees of ‘Radana’ grafted on Caucasian pear seedlings and on quince with intermediate stock yielded better than ‘Radana’ trees composed of Caucasian pear seedling and ‘Pyrodwarf’ interstock. ‘Clapp’s Favourite’ in all combinations had significantly heavier fruits. The highest crop efficiency index had ‘Radana’ on quince with ’Doyenne du Comice’ intermediate stock.

Maximizing Adhesion of Auxin Solutions to Stem Cuttings Using Sodium Cellulose Glycolate

Auxin solutions prepared with sodium cellulose glycolate (SCG; a thickening agent, also known as sodium carboxymethylcellulose) and applied to stem cuttings using a basal quick-dip extend the duration of exposure of cuttings to the auxin and have previously been shown to increase root number and/or total root length on stem cuttings of certain taxa. In a series of three experiments, 3.75-cm stem sections (representing the bases of stem cuttings) of three ornamental plant taxa were dipped to a depth of 2.5 cm for 1 s in solutions prepared with selected rates of SCG using either deionized water or a 10% dilution of an alcohol-based rooting compound (Dip 'N Grow). Each stem section was weighed before and after being dipped in the solution. Regression equations were determined for each experiment and the rate of SCG providing the maximum ratio of SCG solution weight to stem piece weight was determined by setting the first derivative of the regression equation equal to zero. Maximum adhesion of solution was obtained using SCG at 13.35 to 13.71 g·L−1 with an average rate of 13.5 g·L−1.

Action potential propagation through embryonic dorsal root ganglion cells in culture. I. Influence of the cell morphology on propagation properties

1. In this and the companion paper the reliability of action potential (AP) propagation through dorsal root ganglion (DRG) cells was investigated. Experimental data were collected from DRG cells of embryonic rat slice cultures of the spinal cord. A field stimulation electrode was used to elicit an AP in the axon. The propagated AP or, in case of conduction block, its electronic residue (ER), was measured intracellularly in the soma of the DRG cell. 2. The morphological and electrophysiological data combined with published data from voltage-clamp studies were taken to implement a compartmental computer model, which allows a precise description of the propagating AP and the channel kinetics at any point along the axon. 3. The safety factor for conduction was found to be low. Thus failures of AP invasion of the DRG cell soma could occur at sites of impedance mismatch when a hyperpolarizing current was applied, a second stimulus felt into the relative refractory period of the first, or when the axon was repetitively stimulated. 4. The ERs of the failed APs had discrete amplitude levels, suggesting that the failures were always caused at the same site along the axon. These sites of low safety factor were found to be the branch point in the unipolar DRG cell and the entrance of the stem piece into the soma in both cell types, the bipolar as well as the unipolar. 5. A systematic comparison of bipolar and unipolar DRG cells showed that the AP conduction through the latter is more reliable. For large cell bodies, the unipolar configuration is needed for save conduction. 6. Conduction through unipolar DRG cells is faster than through bipolar cells because the electrical load of the soma is masked by the high-resistive stem piece. The length of this stem piece is correlated inversely to the delay caused at the branch point, as the electrical load of the soma is more efficiently masked by a long stem piece.

Identification of in Vitro Resistance of Pigeon Peas [Cajanus Cajan (L.) Millsp.] to Phytophthora Stem Canker

A total of 617 accessions and 40 pigeon pea lines were screened in vitro for their resistance to Phytophthora parasitica. Several entries were found resistant to the pathogen in stem-piece inoculations. Even after injury accessions 394-014, 396-383, 396-356, 396-731, 396-295 and lines 8 AB-2 and 731BD did not show lesions from P. parasitica even when injured.