Abstract
Shoot tips and stem nodes of Asclepias erosa Torr., cultured on a modified (0.5 Ć major salts) Murashige and Skoog (MS) medium containing 0.54 Āµm (0.1 mg/liter) NAA and 44.4 Āµm (10 mg/liter) BA, produced multiple shoots in 5 weeks. Subcultures of the individual shoots on the same medium produced 5-12 new shoots 4 weeks later. Rooting of the resultant shoots was best accomplished by preculturing them for 48 hr on MS medium containing 246 or 492 Āµm (50 or 100 mg/liter) IB A prior to subculturing for 4 weeks on MS medium devoid of growth regulators. The rooted cultures were established successfully in soil. Chemical names used. NAA: 1-naphthaleneacetic acid. BA:N-(phenylmethyl)-lH-purin-6-amine. IBA: lH-indole-3-butanoic acid.
Shoot tips, approximately 3-5mm, were isolated from corms of young greenhouse-grown plants of cocoyam, cultivar South Dade White. After preliminary evaluations, the initiation media evaluated were B5 basal salts supplemented with 0.05 Ī¼M NAA with 5Ī¼M BAP, 20Ī¼M BAP or 2Ī¼M TDZ. The above media were in the form of liquid medium in flasks on a rotary shaker, liquid medium with filter paper bridges, stationary liquid medium without filter paper and solidified medium with 0.4% agar. TDZ stimulated greater growth with multiple shoot formation. Liquid media either in the shaker or stationary form were more effective in terms of growth. Shoots were subsequently evaluated for multiplication with 1Ī¼M TDZ and 5Ī¼M BAP with 0.05Ī¼M NAA producing greater shoot numbers. Over 30 plants have subsequently been rooted and acclimatized under mist or humidity tent.
The resistance of 48 highbush blueberry cultivars and selections to the blight phase of mummy berry disease, incited by the fungus Monilinia vaccinii-corymbosi (Reade) Honey, was examined in relation to percent Vaccinium angustifolium Ait. ancestry, season of fruit maturity, and shoot growth during the primary infection phase. Correlations of percent blighting with percent V. angustifolium ancestry were significant across 3 years, but correlations with fruit maturity were significant in only 2 of 3 years. Correlations of percent blighting with early shoot growth were significant in both years measured, with r values of 0.54 in 1994, 0.83 in 1995, and 0.83 across years. A multiple regression found only shoot growth highly significant for susceptibility and rendered V. angustifolium ancestry and season of fruit maturity nonsignificant. Resistant cultivars exhibiting early shoot elongation suggest that resistance can be either biochemically or escape based.
Many wetland plant species used for aquascaping and wetland revegetation projects are collected from donor wetland sites for planting elsewhere. Increased demand for wetland plants has lead to over-collection and subsequent environmental damage to these donor sites. Micropropagation provides an ecologically sound alternative to field collection and allows for production of under utilized wetland species and genotypes that are either slow-growing or difficult to propagate using conventional methods. Sagittaria latifolia Willd. (Duck-potato), a rhizomatous herbaceous wetland species, was established in vitro from surface-sterilized lateral and terminal rhizome shoot-tips cultured in liquid basal medium consisting of half-strength Murashige and Skoog mineral salts, 0.56 mM myo-inositol and 1.2 Ī¼M thiamine supplemented with 87.6 mM sucrose. Prior to multiplication, responsive Stage I cultures were indexed for cultivable bacteria and fungi. Shoot multiplication occurred in vitro through formation of multiple node rhizomes bearing terminal shoots. Duck-potato exhibited a high sensitivity to relatively low benzyladenine (BA) levels. Maximum rhizome and shoot production occurred from single shoot explants initially cultured on agar-solidified BM supplemented with 4.0 Ī¼M BA for 28 days. However, repeated subculture on BM supplemented with greater than 2.5 Ī¼M BA resulted in increased mortality, reduction in multiplication rate, or production of dormant corms. Consistent shoot multiplication (four to five shoots/explant) was possible in the presence of 1.5 Ī¼M BA. Maximum (100%) acclimatization and rooting was attained by direct sticking of Stage II microcuttings in soilless growing medium contained in 38 cell plugs. Production of salable plants bearing multiple rhizomes was possible within 6 weeks post-transplant. Preliminary observations indicate that corm formation in Sagittaria latifolia may be mediated by photoperiod.
A study was conducted with Prunus Ć incamp `Okame' to evaluate the effects of a pot-in-pot production system compared to a conventional above-ground system and cyclic irrigation on plant growth and water loss. Plants were grown in #7 (26-L) containers with a 8:1 pinebark:sand (v/v) substrate. Cyclic irrigation provided the same total volume of water, but was applied one, three, or four times per day. Final plant height and stem diameter, shoot and root dry weight, total biomass, and root:shoot ratio were all increased for plants grown pot-in-pot compared to above-ground. Multiple irrigation cycles increased stem diameter, shoot dry weight, and total biomass, compared to a single irrigation application. Multiple irrigation cycles decreased the root:shoot ratio. Evapotranspiration was influenced by production system, irrigation, and date. Amount of water lost as leachate was influenced by irrigation and date. Cyclic irrigation resulted in a two-fold decrease in leachate volume. Soluble salts and nitrate-nitrogen in the leachate were influenced by an interaction between production system, irrigation, and date.
Abstract
In vitro cultures were used to study the development of axillary bud and stolon tip explants of cultivated strawberry (Fragaria Ć ananassa Duch.). Explants cultured on Murashige-Skoog basal media containing kinetin at 1, 5, or 10 mg/liter developed into leafy shoots. Low concentration of kinetin (1 mg/liter) promoted the development of both types of explants into single shoots while higher concentration (10 mg/liter) promoted production of multiple leafy shoots developing from axillary buds of the earlier formed leafy shoots. NAA at 1 mg/liter promoted callus growth from both types of explants. Axillary bud explants developed into stolons when cultured on media containing gibberellic acid (GA3) at 5, 10 or 20 mg/liter. Stolon apices developed into leafy shoots while the second axillary stolon buds of the tips were inhibited when the explants were cultured on GA3-containing media. Combinations of GA3 and kinetin induced the development of axillary bud explants into structures intermediate in form between those of stolons and leafy shoots. Stolon apices and stolon axillary buds at the stolon tips developed into leafy shoots and continuing stolons, respectively, when the explants were cultured on a kinetin-containing medium for one week, and then transferred onto a GA3-containing medium. Thus, the developmental pathway of axillary strawberry buds was shown to be responsive to a balance between GA and cytokinins following removal from apical dominance.
Rootstock significantly alters the pattern of shoot growth of pistachio (Pistacia vera) cv. Kerman. Trees on P. atlantica typically produce a single flush of spring growth whereas trees on P. integerrima selection PGI and P. atlantica Ć P. integerrima selection UCB-1 can produce multiple flushes during the season. Terminal buds of shoots on all three rootstocks were dissected during the dormant season to determine the number of preformed nodes. Data indicate that there are 8-9 nodes preformed in the dormant terminal bud of shoots from Kerman trees and that this number is independent of rootstock, canopy location, crop load, and shoot carbohydrate concentration, suggesting genetic control. This number corresponds with the number of nodes typically found on a shoot at the end of the spring growth flush. Unlike the spring flush which is preformed in the dormant bud, later flushes are neoformed, that is, nodes are initiated and extended during the same season. Neoformed growth depends on current season photosynthates and may compete with fruit growth for available resources. Neoformed growth is sensitive to water stress and trees on all three rootstocks grown under two levels of regulated deficit irrigation showed a reduction in both the number and length of neoformed shoots. Preformed shoot growth did not appear to be reduced under water stress conditions, supporting the hypothesis that preformed shoots are more dependent on environmental conditions during the season they are initiated than during the season they are extended. Additionally, preformed shoots on well irrigated trees were similar in length for all rootstocks, further supporting the idea that preformed shoots are under genetic control and are not easily manipulated.
Under typical South African growing conditions, `Fuji' apple (Malus domestica Borkh.) trees are characterized by strong apical dominance during the first few years after planting. This, together with the current lack of suitable precocious rootstocks and the tip-bearing habit, causes willowy āblind woodā growth with few flowering positions, and delays bearing until the third leaf when a crop of less than 10 tons/hectare can be realized. Promalin (GA4+7 and benzyladenine, Abbott Laboratories) was used in combination with apical meristem defoliation and Agral or Armoblen as surfactant/penetrant to induce sylleptic shoot growth in an effort to increase tree complexity (i.e., branching) without having to resort to pruning, which is dwarfing and delays bearing. The treatments were tested on `Fuji' grafts, 1-year old trees and 2-year old trees in the 1993ā1994, 1994ā1995, and 1995ā1996 seasons, respectively. Concentrations tested were 0, 500, 750, or 1000 ppm, as single or multiple applications in spring. In all trials, randomized, complete block designs were used. Control trees had few, if any, sylleptic shoots or spurs, whereas Promalin in combination with leaf removal or in combination with Armoblen caused significant sylleptic growth to occur. Generally, multiple applications spaced fortnightly, gave best results. Sylleptic shoots were ā15 cm long, terminated in a reproductive bud, and did not influence the length of the āmotherā shoot or the trunk circumference. Based on these results, a combination of multiple applications of 500 ppm Promalin with Armoblen as penetrant, and no leaf removal, is being tested semi-commercially this season.
Abstract
Leaf explants of broccoli [Brassica oleracea L. (Italica group)] produced either callus, roots, shoots, or both on Murishige and Skoog media (M&S) media with 4.0 to 6.0 mg/liter kinetin and from 8.0 to 9.0 mg/liter indoleacetic acid (IAA). Sections of leaf rib developed callus and then multiple shoots and roots on media with 8.0 to 10.00 mg/liter kinetin and 9.0 to 10.0 mg/liter IAA. Stem explants formed very little callus, but differentiated roots and shoots with 3.0 to 20 mg/liter kinetin and 9.0 to 10.0 mg/liter IAA. Successful transplanting to soil was achieved with all explants.
Prohexadione-Ca (BAS 12511W or Apogeeā¢ Plant Growth Regulator) acts within a plant by blocking the biosynthesis of growth-active gibberellin. The result is decreased cell and shoot elongation; thus, vegetative growth in apple trees can be reduced. Air blast applications of prohexadione calcium were made in the Spring 1998 in commercial orchards. Application rate was 125 ppm a.i. applied twice beginning at 5 to 12 cm of new shoot growth. Reduction of shoot growth averaged 45% across locations. As a result of reduced vegetative growth, dormant pruning was reduced. In total, significant benefits to the grower included reduced pruning costs in addition to other positive effects such as improved light penetration and enhanced resistance to some pathogens. Research will continue with the effect of prohexadione-Ca on pruning in multiple year studies.