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Abstract
Calcium, K and Mg content of interclonal juniper grafts were determined using electron microprobe x-ray analysis of tissue in the immediate vicinity of the graft union. Considering xylen concn as a measure of mobile elements, Ca accumulated in the rootstock while K and Mg moved readily through the graft union. In phloem tissue, distribution was generally equal between rootstock and scion for all elements; Mg being slightly greater in the stock. In cortical cells, Ca accumulated in the scion. Microprobe data indicated a decreasing order of rootstock accumulation to be Ca, K, and Mg.
Abstract
Comparative studies of clonal anatomy revealed visible differences in medullary ray cell diam in juniper cultivars with different chromosome numbers. Histological studies, made at 10-day intervals for 60 days after grafting showed no differences in developmental sequence but only differences in rate at which each stage occurred. Callus tissue form ation began 10 - 20 days after grafting; first in ‘Fountain’ and last in ‘Pfitzeriana Kallay’. Isodiametric cells from uninjured cambia appeared by the 20th day except with ‘Pfitzeriana Kallay’ scions. By an alternating series of radial and tangential divisions, these cells overwalled the injured graft surfaces, but was less pronounced in closely fitted grafts. Overwalling cells did not occur in ‘Pfitzeriana Kallay’ until 30 days after grafting. By 40 - 50 days, overwalling cells began, by radial divisions to produce organized cells which filled voids between graft partners and crushed intervening callus. Mixing of newly formed cells between stock and scion cambia occurred 50 - 60 days after grafting. These cells assumed the spindle-shape of typical tracheids and were oriented into a “cambial bridge.” New, normally oriented xylem subsequently formed from this new cambial tissue. In typical grafts, most new tissue arose from the understock prior to the 50th day after grafting. At 60 days, contribution from stock and scion were equivalent. Adjacent walls of mixed graft tissue were found to be unmodified and appeared as paired structures each with a middle lamella and secondary wall thickenings. Abnormally large numbers of pits were observed at the graft union.
`Redhaven' peach tree plantings were established in 1985 to compare tree densities (299 trees/ha to 1794 trees/ha) and training systems (Open Vase, Central Leader, Y-shaped, Palmette Trellis, Tatura Trellis, and MIA Trellis). Tree trunk growth (diameter) was significantly less as the population of trees increased. Trunks of trees trained to the Open Vase were larger than Central Leader or Y-shaped trees. In 1988, yields per ha increased as tree density increased. Trees trained to the Tatura Trellis (897 trees/ha) had the highest yields (27.7 t/ha). Trees trained to the Central Leader and planted at 1794, 897, and 598 trees/ha had next highest yields of 24.5, 21.4, and 24.3 t/ha, respectively. By the 6th year, yield differences were not generally related to tree density. The top yielding systems were Open Vase (598 trees/ha) and Tatura Trellis (897 trees/ha) with yields of 32.1 and 29.0 t/ha, respectively. Trees trained to Open Vase had higher yield efficiencies (kg/cm2 limb CSA) in 1991 than trees in other systems-spacings and had yields of 23.6, 27.4, and 32.1 t/ha for plant densities of 299, 448 and 598 trees/ha, respectively.
Abstract
Gardenia jasminoides Ellis and Ilex crenata Thunb. ‘Compacta’ were field-grown with 4 irrigation rates based on 0%, 25%, 50%, and 100% replacement of net evaporation from a class A pan. Irrigated gardenia were larger than nonirrigated gardenia, and those grown with 50% and 100% replacement of net evaporation had greater total root growth than nonirrigated plants. Root number, root dry weight, and fibrous root number in a 20-cm rootball were generally greater with irrigated plants than nonirrigated plants. Ilex crenata shoot growth was greater also with irrigation versus nonirrigation. Based on this data, 25% replacement of net evaporation resulted in plants of both species being similar to higher irrigation rates.
Abstract
‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) on seedling rootstock were grown with trickle and sprinkler irrigation, both operated at high frequency of irrigation (daily). Trees with trickle irrigation developed lower leaf water potentials and produced less vegetative growth than trees with sprinkler irrigation, but fruit and productivity were similar. Apples from the trickle-irrigated trees had less water content and higher soluble solids than those from sprinkler-irrigated trees. Titratable acidity tended to be lower and both red color in ‘Delicious’ and yellow color in ‘Golden Delicious’ tended to be higher in fruit from trickle-irrigated trees than from sprinkled trees; firmness at harvest was similar regardless of irrigation procedure. Storage life was not influenced consistently by irrigation. Where differences did occur, the fruit from trickle-irrigated trees was softer after storage. Changes in fruit quality similar to those observed in trickle-irrigated trees were produced by imposing, through high frequency deficit irrigation with sprinklers, similar moisture deficits on apple trees, as measured by leaf water potential.
Prohexadione-Ca (BAS 12511W or Apogee™ 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.
'Maffei 15' baby lima bean seeds were sown every 6 cm in rows 76 cm apart to yield a nominal stand of 215,000 plants/ha at two locations in Delaware over 2 years. Seedlings were thinned within 2 weeks of planting to provide 0%, 16.7%, 33.3%, and 50.0% stand reduction at two in-row spacing patterns to determine subsequent effects on vegetative and reproductive growth. Shoot fresh weight per square meter was decreased only in 2003 by 21% and bean fresh weight per square meter was decreased only in 2004 by 13.8% when plant stand decreased to 50%. This disproportional vegetative and reproductive growth response to stand reduction resulted from a compensatory linear increase in shoot fresh weight, usable pod number, and bean fresh weight of individual plants. Thus, 'Maffei 15' lima bean tolerates a considerable loss of plant stand with little or no effect on yield.