Search Results
You are looking at 61 - 70 of 89 items for
- Author or Editor: George C. Martin x
Abstract
‘Bartlett’ spurs carrying seedless or seeded fruits produced relatively high percentages of flower buds. Spurs carrying seedless pears for 31 days after bloom produced more flower buds than did spurs carrying seeded pears. Also, the exudate from seedless pears had more growth-promoting activity. Beyond 31 days there were no consistent differences in flower bud formation in spurs carrying seedless vs. seeded pears. Carrying seeded pears 31 days largely inhibited flower bud initiation in ‘Winter Nelis’. There was an inverse relationship between flower buds and seeds in fruits on spurs of both varieties defruited 61 days after bloom. The relationship was not distinct for spurs carrying fruits longer. Fluctuations in the growth-promoting activity of the fruit exudate indicate that the hormonal status, at the time the spur was defruited, influenced flower bud formation more than did number of fruits, seeds, or length of fruit-carrying period.
Abstract
Kernels from Juglans regia walnuts stratified at 0°C were sampled at weekly intervals and extracted with methanol. The extracts were partitioned into 4 phases which were water, neutral ether, acidic ether and acidic butanol, then bioassayed for cytokinins, gibberellins, auxins and inhibitors. No cytokinins nor gibberellins were found in the tissue. There was activity analogous to that from auxins. An inhibitor which diminished during stratification was found. This inhibitor is believed to be abscisic acid, on the basis of UV absorption spectrum, Rf values established by co-chromatography on paper and silica gel plates, and derivatives analyzed by gas liquid chromatography.
One- and three-node nectarine explants were compared with intact potted units of similar dimension. The explants and intact plants performed similarly as judged by rate of leaf photosynthesis, leaf and fruit respiration, and changes in fresh and dry weights. Water loss and transpiration were less in explants than intact plants after 24 h. Explants with fruit of nectarine, olive, and prune were used to evaluate uptake and distribution of 14C-labeled paclobutrazol (PBZ), daminozide, and sucrose in plant parts. These comparisons reveal that the explant system is useful for primary testing of hypotheses, screening of chemicals, and evaluating species response for later testing of selected parameters in the field. Three-node explants containing fruit are reliable for experiments lasting up to 4 days. Chemical names used: succinic acid 2,2 dimethylhydrazide [daminozide (SADH)]; β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol [paclobutrazol (PBZ)].
The objective of this investigation was to determine the dynamics of carbohydrate use as revealed by soluble sugar and starch concentration in leaves, inflorescence buds, rachises, nuts, current and 1-year-old wood, and primary and tertiary scaffold branches and roots (≤10 mm in diameter) of alternate-bearing `Kerman' pistachio (Pistachia vera L.) trees that were in their natural bearing cycles. Two hypotheses were tested. First, carbohydrate concentration is greater early in the growing season in organs examined from heavily cropping (“on”) than light cropping (“off”) trees. This hypothesis was affirmed as judged by soluble sugar and starch concentration in leaves, inflorescence buds, rachises, nuts, current and 1-year-old wood, and primary and tertiary branches and roots of “on” compared to “off” trees. Second, carbohydrate concentration remains high in “on” tree organs as the first wave of inflorescence bud and nut abscission occurs early in the growing season. This hypothesis was also affirmed. In fact, soluble sugars and starch remained high in “on” trees through full bloom FB + 60 days (FB + 60) as inflorescence bud and nut abscission occurred. In the persisting “on” tree inflorescence buds, sharp decreases in soluble sugars and starch were evident by the final sample date when “off” tree inflorescence buds contained a 13 times greater concentration of soluble sugars and starch than “on” tree buds. At that time, “off” tree inflorescence buds contained 50% more dry mass than “on” tree inflorescence buds. After FB + 60, “on” tree soluble sugars and starch declined in all organs as nut growth occurred. During the same time period, organs of “off” trees began to accumulate greater concentrations of soluble sugars and starch and exceeded concentrations measured in organs of “on” trees.
Isothermal microcalorimetric measurements of metabolic heat rates of `Kerman' pistachio (Pistacia vera L.) individual inflorescence buds, current-year and 1-year-old shoots were used to investigate the roles of current and reserve photosynthates in the abscission of inflorescence buds. In the early stages of development metabolic heat rates of individual inflorescence buds were two and three times those of individual current-year and 1-year-old shoots respectively. Individual shoot organs (1-year-old shoots, current-year shoots, and inflorescence buds) sampled from “on” trees had higher metabolic heat rates than similar individual organs sampled from “off” trees. Artificial shading of pistachio trees for 14 days in early June depressed metabolic heat rates of individual inflorescence buds within 24 h, but there was a delay of 4 days before the decline in metabolic heat rates of individual current-year and 1-year-old shoots. This suggests that metabolic heat rates of individual inflorescence buds apparently depended on currently fixed photosynthates.
Early fall (September) defoliation and late spring (early June) shading of “off” and “on” pistachio trees were used to test two hypotheses: that 1) fall defoliation would reduce carbohydrate storage sufficiently to suppress spring growth and 2) spring shading would reduce carbohydrate status and increase inflorescence bud abscission. Defoliation suppressed initial leaf area expansion the following spring on current year shoots of “off” but not “on” trees respectively. Suppression of leaf size was correlated with the initial low concentration of carbohydrates in organs of individual branches of the tree. Fruiting and artificial shading in June had more dramatic effects on growth parameters than defoliating. Shading “off” trees for 14 days in early June accelerated abscission of inflorescence buds, reduced dry mass of individual leaves, buds, current year and 1-year-old shoots. Shading also reduced the concentration of total nonstructural carbohydrates (TNC) of these organs in “off” and “on” trees. Fruiting suppressed leaf size and leaf dry mass by 20% and 30% among individual branches of undefoliated and defoliated trees respectively. Low carbohydrate concentrations in individual branches and inflorescence buds following shading were closely correlated with the abscission of inflorescence buds.
We investigated the development of leaf area (LA) and the distribution of dry matter within branches of 25-year-old, alternate-bearing `Kerman' pistachio (Pistacia vera L.) trees that were in their natural “on” (heavy) or “off” (light) bearing cycles to determine the immediate and delayed effects of fruiting on shoot growth. Compared to “off” trees, individual leaves of “on” trees were greater in number and expanded twice as fast during the first 30 days after full bloom (FB) (FB + 30). Mature, fully expanded leaves of “on” trees were smaller (124.1±3.26 cm2) than those from “off” tree (163.3±3.40 cm2), indicating delayed demands of fruiting on initial leaf growth. Total LA per current shoot was greater in “on” than “off” trees because shoots of “on” trees averaged eight leaves, compared with six for “off” trees. More inflorescence buds per shoot (seven vs. three buds) abscised from “on” than from “off” trees. About 60% of the young developing nuts had abscised by FB + 30 when they weighed <250 mg each and another 25% abscised between FB + 30 and FB + 60 when individual nuts weighed ≈400 mg. The average total dry mass (DM) of individual branches of “on” trees increased 1322% (5·9 to 83·9 g) compared to 598% (4·2 to 29·3 g) in “off” trees. Besides nuts, leaves accumulated the greatest amount of dry matter within individual branches followed in decreasing order by current wood, 1-year-old wood, and inflorescence buds. DMs of individual leaves of “on” trees averaged between 15% and 48% greater than leaves of “off” trees. “Off” trees invested 4.6 g of dry matter into individual 1-year-old wood and 2.1 g into current wood. “On” trees, however, invested 1.3 g of dry matter into 1-year-old wood and 4.3 g of dry matter into current wood. One-year-old wood was an important major source of carbohydrates for developing leaves, current wood, rachises, and nuts. The immediate demands of fruiting on individual components of a branch were measured as losses in DMs. Individual leaves, current wood, 1-year wood, and rachises lost 1.1%, 0.3%, 1.1%, and 1.0%, respectively, of the average total DMs of individual branches of “on” trees. This loss was equivalent to 5.7%, 5.9%, 26.7%, and 16.4%, respectively, of the seasonal average peak DMs of the respective individual components of the branch.
Abstract
Containerized peach [Prunus persica (L.) Batsch.] seedlings were grown in the greenhouse at three water levels [25%, and 100% field capacity (FC)] with experiments duplicated in Bologna, Italy and Davis, Calif. One group of the seedlings was treated with 0.1 g active ingredient (a.i.) paclobutrazol (PBZ) applied as a soil drench, whereas the second group received water only. Addition of PBZ suppressed shoot growth and leaf area more than reduced water content alone. PBZ reduced root fresh and dry weights and total water consumption. At 0600 and 1200 hr, PBZ increased stomatal conductance at 100% FC; later that same day stomatal conductance decreased. At 50% and 25% FC, PBZ decreased stomatal conductance compared to controls at all times measured. Chemical name used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol).
Abstract
In each of three years, paclobutrazol was soil-injected at about a 15 cm depth and 1 m from the ‘Flavorcrest’ peach [Prunus persica (L.) Batsch] tree trunk. In the randomized complete block design, many significant differences between paclobutrazol-treated trees and controls were measured in the following categories: reduction of canopy growth, increased numbers of vegetative and floral buds in the lower portions of the tree, elimination of the need for summer pruning, increased hand fruit thinning time in two of three years, increased fruit yield and size, advanced fruit maturity, decreased leaf K, and increased leaf Ca. Paclobutrazol increased cumulative yield over controls from 30.1 to 41.8 t·ha−1 for the 3-year experimental period. This yield increase exceeded the controls by at least 22%, 71%, and 76% for 1984, 1985, and 1986, respectively, and occurred without measurable fruit quality loss, except for soluble solids, which were decreased in two of three years. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Abstract
Walnuts (Juglans regia L.) with and without (2-chloroethyl)phosphonic acid (ethephon) treatment were harvested at the earliest practical time and 3, 7, and 10 days later. With both treatments a delay in harvest resulted in kernels of lower quality and subsequent value. Furthermore, lower quality was found in earlier maturing than in later maturing walnuts when harvested from the same tree on the same day. In all comparisons kernels from ethephon-treated nuts were of higher value than controls. Walnuts left in the drier beyond the time necessary to remove excess moisture lost negligible quality and value.