cultivars and rootstocks and differ in their use of plant protection products, we used the same approach as that already found in tree pruning handbooks and show only the most common tree responses in the form of changes in tree crown structure without
`Earliglow' strawberry (Fragaria xananassa Duchesne) plants were frozen to -5 or -50C to examine the distribution of ice in the crowns. Anatomical studies were also performed to characterize tissue growth in a greenhouse at 4, 8, and 15 weeks after freezing to -5C. Ice masses observed in fresh crown tissue corresponded to the presence of extracellular tissue voids in specimens fixed for scanning electron microscopy (SEM). Voids were present near the peduncle and adjacent to the vascular system in crown tissue. After plants were grown in the greenhouse, cell division and enlargement were observed near the voids in crowns subjected to -5C. By 15 weeks after freezing, a few small extracellular voids remained in the crowns. Tissue voids were also present in crowns of plants frozen rapidly to -50C and subsequently thawed. Cells in the crown of these plants were intact and did not appear collapsed after exposure to -50C, a lethal temperature.
Short productive lifespan is a major problem with asparagus (Asparagus officinalis L.), whether harvested in the spring or forced in late summer in coastal South Carolina. A modification of the Taiwanese system of mother stalk (MS) culture might enhance asparagus longevity and yield. The objective of this research was to determine if modified MS culture improved plant survival and yields in spring or summer-forced harvests compared with conventional spring clear-cut (CC) harvesting or with nonconventional summer-forced CC harvesting. `Jersey Giant' asparagus was harvested for 3 years (1994-96) using the following harvest systems: 1) spring CC (normal emergence in February in this location); 2) spring MS followed by summer MS (mow fern down on 1 Aug. and establish new mothers); 3) spring MS only; 4) summer CC only (mow fern on 1 Aug. and harvest); and 5) summer MS only. All systems were harvested for ≈7 weeks. All MS plots produced 40 mother stalks per 12-m row length each year before harvesting began. All mother stalks were trellised and tied to prevent lodging. Three-year total yields (kg·ha-1) and stand reduction (%) for nonharvested controls, spring CC harvesting, spring MS culture, spring MS combined with summer MS, summer CC, and summer MS were: 0 and 54%, 1621 and 96%, 779 and 99%, 1949 and 86%, 4001 and 58%, 3945 and 58%, respectively. All spring harvesting systems failed because by midsummer, aged fern, harvest pressures, and, apparently, higher rates of crown respiration reduced crown carbohydrate reserves. Yearly repetition of these stresses ultimately killed the spring-harvested plants. The MS culture did not ameliorate stand loss by significantly increasing carbohydrate reserves. Yields of summer-forced asparagus were consistently acceptable because aged ferns were removed at about the time they apparently became inefficient photosynthetically. After termination of the summer harvest season and with recovery in the following spring, ample carbohydrates were produced well before summer forcing began again in August the following year. Therefore, plant longevity was better sustained by summer forcing than by traditional spring harvesting.
Dormant, intact crowns were used to determine the cold hardiness of the herbaceous perennial Heuchera sanguinea `Chatterbox'. Crowns were placed in moist cheesecloth, wrapped in aluminum foil, and subjected to -4,-6,-8,-10,-12,-14, -16, or -18C in a programmable freezer. Regrowth quality ratings and dry-mass measurement decreased linearly with temperature. No regrowth was evident from any crown exposed to -12C or lower temperatures. Freezing dormant plant crowns proved an efficient and reliable technique for estimating cold hardiness of Heuchera `Chatterbox'.
During Fall 2003, a study similar to that of Fall 2002 was conducted to determine the effect of crown manipulation on shoot production in four cultivars of daylily. Three crown manipulation treatments: (1) the shoot cut back two centimeters from crown, (2) the shoot cut back to the crown, and (3) shoot cut back to the crown and scooped out were compared to a control. Four daylily cultivars, `Bull Durham', `Amber Lamp', `Angus McLeod', and `Alvatine Taylor' were used in this study. After eight weeks of observations, the results showed that the cut back to crown treatment caused a significant increase in the number of shoots when compared to the control and other two treatments. Shoot production for the cultivar `Angus McLeod' was significantly better than the other cultivars. Results obtained for Fall 2003 study were similar to that of Fall 2002. These results imply that cutting the shoots back to the crown in some daylily cultivars could possibly be used to enhance multiplication of daylilies during propagation.
Abstract
Resistance to Fusarium crown and root rot (Fusarium oxysporum f. sp. radicis-lycopersici) in the tomato (Lycopersicon esculentum Mill.) was inherited as a monogenic dominant gene in a cross between the breeding lines 89-1 (resistant) and 1239A (susceptible).
Abstract
African violets (Saintpaulia ionantha Wendl.) are propagated commercially by leaf cuttings with or without a petiole (3). Laurie and Kiplinger (4) reported that leaves propagated without petioles produce more crowns. Developing shoots or crowns (plantlets) with roots usually are divided and handled as young plants. In one variation of this method the roots are removed from the shoots, the shoots are graded and the graded shoots are rerooted to obtain uniform plants. This method requires numerous shoots.
Abstract
Asparagus (Asparagus officinalis L. Cv. Cal. 711) grown both from seed and 1-year old crowns was maintained in a zero-tillage cultural system for 4 years and compared with that grown in a conventional tillage system. In the first 3 harvest seasons, yields of asparagus produced from crowns were increased 27% in the zero-tillage system. Asparagus from seed yielded as much as that from crowns after the third year, but spear size was appreciably smaller. Paraquat (1,1’-dimethyl-4,4’-bipyridinium ion) in combination with either simazine (2-chloro-4,6-bis(ethylamino)-s-triazine), monuron (3-(P-chlorophenyl)-1,1-dimethylurea), or terbacil (3-tert-butyl-5-chloro-6-methyluracil) provided excellent weed control during each growing season without injuring asparagus. Rotary chopping was a satisfactory method for returning mature brush to the soil. Additional advantages of zero-tillage were a reduction in volunteer asparagus seedlings, improved late season weed control, and less mechanical injury to crowns and buds. This cultural system provided excellent weed control in fields produced by direct seeding where crown depth was shallow and tillage impractical.
Abstract
In 3 separate experiments, the effects of container types, transplant age, and growing media on asparagus (Asparagus officinalis L.) transplant quality were determined. These transplants then were field planted to determine the effects of propagation methods on plant growth after one growing season. Transplants grown for 10 weeks in deep peat pots (10 cm deep, 177 cm3, and 364 plants/m2) produced crowns and fern of higher fresh and dry weight than other containers (ranging in depth from 5.5 to 7.6 cm, in volume from 53 to 186 cm3, and plant density/m2 from 277 to 1624). Shoot and root growth of 7-, 8.5-, and 10-week-old transplants (grown in identical containers) were similar, but crown fresh and dry weight were reduced for 6-week-old transplants. Ten-week-old transplants originally broadcast-seeded in flats of 1 vermiculite: 1 peat medium (v:v) produced more roots, buds, shoots and fern and crowns of greater fresh and dry weight than those grown in 1 peat : 1 perlite or 1 perlite : 1 vermiculite media. At the end of the growing season, plants originally grown in deep peat pots were superior in number of shoots and fleshy roots, and crown and fern dry weight to those grown in other container types, to transplants of various ages, and to bareroot transplants.
Abstract
The viability of freeze-stressed Fragaria × ananassa Duch. cv. Catskill strawberry crown tissues was evaluated using triphenyl tetrazolium chloride (TTC) reduction and oxidative browning. Both tests showed the medulla tissue to be the most susceptible to low-temperature injury, while vascular tissue was least susceptible. TTC reduction appears to be negatively related to tissue browning, and both provide similar results pertaining to tissue viability.