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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.

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.

Previous studies have demonstrated that phosphorus, which stimulates ethylene biosynthesis, induces abscission of olive leaves directly without the involvement of ethylene. In the present study this possibility was further explored by comparing the effects of an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), and an ethylene action inhibitor, 2,5-norbornadiene (NBD), in olive [Olea europaea (L.) `Manzanillo'] and citrus [Citrus sinensis (L.) Osbeck `Shamouti']. In olive, leaf abscission was always induced in the presence of KH2PO4 with or without AVG and NBD (alone or in combination), but it was much more pronounced when KH2PO4 was applied alone. In citrus, KH2PO4 did not induce leaf abscission in the presence of NBD during the first 48 (detached shoots) or 60 hours (leaf explants) despite the high levels of ethylene production by the tissues. Our results demonstrate that phosphorus can, at least partly, act independently of ethylene action in inducing leaf abscission in olive but not in citrus.

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.

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

Fruit removal force (FRF) and percent leaf drop (LD) of fruit-bearing olive (Olea europaea L.) shoots were examined 120 hours after being sprayed with ethephon at 600 mg·liter-1 and held under controlled-environmental conditions analogous to those found in the field in California at harvest time in mid-October. FRF was not significantly affected by solution pH, but FRF of all treated shoots was significantly lower than that of the untreated controls. Only at pH 5 was percent LD significantly greater than that of the controls, but, of the shoots treated with ethephon, the lowest percent LD occurred at pH 3. Percent LD after treatment with ethephon at pH 3 was not affected by application time, but FRF was significantly less than the controls' when shoots were treated at 7 am or 12 pm but not at 5 pm or 10 pm. Adding NAA to the ethephon solution raised FRF and adding BA lowered FRF compared to ethephon alone. Adding NAA or BA did not mitigate percent LD significantly. Adding BA advanced anthocyanin production in fruit. Ethephon penetration of rachides was ≈70% that of petioles. Correlation between ethephon penetration of petioles and percent LD was greater than that between penetration of rachides and FRF. Correlation was significant for both tissues only in the 12 pm pH 3 treatment; correlation was also significant for petiole penetration and percent LD at pH 5. Autoradiographic studies of the 14C-ethephon penetration showed no pH effect, greater penetration into petioles than rachides, and that radioactivity was limited largely to intercellular spaces, with accumulation in vascular bundles, especially xylem. Regardless of treatment, FRF and percent LD are negatively correlated (r2 = 0.615). Mean results to be expected using ethephon as an olive harvest aid under these conditions are an FRF of ≈3 N and a percent LD of ≈15%. The desired low FRF and percent LD were obtained by applying ethephon alone at pH 3 at 7 am. Raising ethephon solution pH does not increase harvest effectiveness. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon), naphthalene acetic acid (NAA), 6-benzylaminopurine (BA).

Adding Al2O3 to 8-hydroxyquinoline citrate (8-HQC) solution did not alter the sensitivity of the leaf abscission zone to external ethylene. Exogenous ethylene at 791 nl·liter-1 for 72 to 120 hours and at 193 nl·liter-1 for 120 hours induced leaf abscission, whereas no leaf abscission occurred at 47 nl·liter-1 for 72 to 120 hours. Ethylene at 791 nl·liter-1 for 72 to 120 hours increased ethylene evolution, but the amount of ethylene evolved from the explants does not seem to be enough to induce leaf abscission. Three different ethylene inhibitors—aminooxyacetic acid (AOA), CoCl2, and aminoethoxyvinylglycine (AVG)—were used to determine whether P-induced leaf abscission was mediated through elevated ethylene evolution. Although AOA and CoCl2 failed to inhibit ethylene evolution from the explants stem-fed with NaH2PO4, AVG inhibited ethylene evolution. Each inhibitor, except 5 mm CoCl2, promoted leaf abscission when administered alone or with P. Our results reveal that P-induced olive leaf abscission may occur without elevated ethylene evolution. At 40 or 75 mm NaH2PO4, abscission did not occur until explants were removed from N2 and placed in ambient air.

To investigate the effect of diffusional limitations on the cure of thermosetting polymers, a modeling strategy has been developed for estimating the average diffusion coefficient of the molecular species in the curing systems. The modeling is based on the dielectric measurement of the mobility-related properties including the ionic conductivity and the dipole relaxation time. It was shown that the ionic conductivity is the dominant factor in the diffusion model valid in the pregel stage, while the dipole relaxation time may be utilized to evaluate the diffusivities in the postgel stage. This approach may find applications in the study of the diffusion-controlled cure kinetics and structure property relationships in thermosetting polymer systems

The molecular diffusion and the diffusion-controlled kinetics during curing of an epoxy-amine resin have been studied. The diffusivity was estimated using an approach based on the dielectric analysis of the resin system. At low conversions, the decline of the diffusion coefficient is relatively slow while, at higher conversions, the diffusivity drops significantly even with a small advancement of cure. The normalized diffusion coefficient was in agreement with the predictions of the free-volume model of Huguenin and Klein but disagrees with those of the cooperative rearrangement model of Havlicek and Dusek. This discrepancy was attributed to an assumption of the cooperative rearrangement model

When continuously stem-fed with 75 mm NaH2PO4, `Manzanillo' olive explants showed significant leaf abscission after 48 hours; by that time 1.042 mg·g-1 fresh weight P had accumulated in the abscission zone (AZ). The potential contribution of ethylene to phosphate-enhanced abscission was investigated using aminooxyacetic acid (AOA), an ethylene-synthesis inhibitor, and by measuring ethylene evolution in phosphate-treated explants. In combination with NaH2PO4, AOA did not affect leaf abscission. Though ethylene evolution from explants increased as leaf abscission was initiated, it was about two orders of magnitude less than the concentration necessary to induce leaf abscission as judged by exogenous treatments. Based on leaf-abscission kinetics, we have concluded that the mechanism of P-induced abscission is independent of gross measurement of evolved ethylene, but we cannot rule out ethylene confined to the AZ itself. When evaluated for P-induced leaf abscission, leaves of `Manzanillo' and `Sevillano' abscised earlier than `Ascolano' and `Mission'.

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 14 C-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)). Physiological experiments with perennial plants in the field are made difficult by variable climatic conditions and orchard prac- tices. Partial climate control is possible in the laboratory, but mature bearing trees cannot be accommodated in such a setting. A laboratory model system is needed using excised plant parts that will resemble plant metabolism when attached to a tree in the field. Such a model system affords primary testing of hypotheses con- cerning physiological response to horticultural or chemical treat- ment. An excised plant model system, as compared to large orchard trees, would be useful and less expensive in studying the complex interaction and multifactorial controls necessary for difficult interpretations (Zucconi and Bukovac, 1989). Greenhouse containerized seedlings or grafted fruit trees grown on solid substrates or liquid media are useful for different applica- tions of unlabelled or labelled chemicals and for checking their mobility and stability (Intrieri and Ryugo, 1974; Sterret, 1985; Richardson and Quinlan, 1986; Early and Martin, 1988a,1988b). The presence of fruit adds further complexity to the model plant; still, small, potted, bearing apple trees have been used to evaluate growth substance movement and activity (Biasi, 1990; Samaraweera and Hill-Cottingham, 1980). The purpose of our work was to 1) achieve a high level of simplicity and reliability using a fruiting explant model system to carry out short-term physiological stud- ies; 2) verify the reliability and usefulness of the excised model plant system using 14 C forms of daminozide and paclobutrazol (PBZ) and 3) compare daminozide and PBZ transport and accumu- lation with that of 14 C-labeled sucrose, a compound distributed all over the plant. The hypothesis we tested was that the fruiting excised model plant system could be used as a primary screening test to determine the ultimate accumulation and distribution of candidate chemicals to be tested later in the field.

Citrate-phosphate buffer induced olive (Olea europaea L.) leaf abscission at pH 3, 5, or 7. Of several sources of P-induced leaf abscission, NaH2PO4 was the most effective. Sensitivity to P was shown by leaf abscission, leaf desiccation, or both among 32 species representing 22 genera. Applied P accumulates in petioles, but its effect on abscission does not seem to depend on ethylene production. The low P content in the ethephon molecule may have an additive effect in ethephon-induced abscission. Stem-fed NaH2PO4 or ethephon resulted in total leaf and fruit abscission. Of the chemicals applied as a foliar treatment, only NaH2PO4 caused fruit abscission with minimal leaf loss. Adding Al2O3 to adsorb P in treatment solutions delayed the abscission effect of ethephon and NaH2PO4. Adding glycerol to NaH2PO4 increased fruit abscission from 50% to ≈80% and leaf abscission from ≈9% to 18%. The presumed effect of glycerol is from slowing the drying rate and thereby increasing P penetration into the fruit abscission zone. The pedicel-fruit cavity is a collection basin for spray accumulation that is not present in the leaf petiole attachment to the stem. This morphological difference probably leads to greater absorption of abscission-inducing materials by fruit. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

A once-in-a-century cold front, expressed as an advective freeze, damaged ‘Manzanillo’ extensively statewide. ‘Ascolano,’ ‘Sevillano’ and ‘Mission’ received minor damage. Damage included tip burn, defoliation, bark splitting and limb dieback. The next growing season some new leaves were deformed and flower bud damage could be found. Outbreaks of olive knot had also been expected, but few occurred.

Naturally occurring postanthesis abscission in olive (Olea europaea L. Manzanillo) results in approximately 99% loss of flowers. Ethylene gas treatment induces sequential abscission of flowers, rachis branches and internodal sections, and peduncles of mature (expanded) inflorescences on shoot explants. Treatment with 2-chloroethyl phosphonic acid (ethephon) triggers sequential abscission of flowers and peduncles of mature inflorescences but only very infrequently rachises and never internodal sections. Immature (not fully expanded) inflorescences on shoot explants abscise intact in response to ethylene gas or ethephon. Sites of floral abscission on trees are limited to bracts, petals, individual flowers, and peduncles. With the exception of bracts, floral organs on trees do not abscise until after pollination. Naturally occurring abscission is preceded by plasmolysis of abscission zone cells, loss of cell wall materials as evidenced by changes in stain intensity, and lacunar cell separation. Abscission of...

Olive (Olea europaea L.) field experiments involving natural flower and fruit populations are fraught with variability, resulting in large coefficients of variation. We provide evidence that coefficients of variation can be reduced successfully by judiciously selecting four experimental twigs per tree and using only those twigs with an internodal growth ≥2 cm, two inflorescences per node, and that are selected from trees with near- maximum bloom density. Although counting flowers at full bloom may establish the population uniformity, only a single node; e.g., node 5, is needed for analysis. Increasing the number of trees will reduce variance more than increasing the number of twigs or nodes. Olive field experiments designed to mea- sure flower production and fruit persistence are complicated by large coefficients of varia- tion. In our field experiments, we have en- countered coefficients of variation >100. The investigations of Rallo et al. (1981) have done much to describe the olive flower and fruit population and its persistence characteristics; they compared fruiting habits of 'Manzanillo' (strongly biennial), 'Swan Hill' (flowers an- nually but fruitless), and 'Rubra' (annually fruitful). They found that 1) imperfect flowers of each cultivar abscised immediately after full bloom; 2) the percentages of flowering twigs bearing mature fruit were 91%, 55%, and 0% for 'Manzanillo', 'Rubra', and 'Swan Hill', respectively; 3) abscission occurred in 'Manzanillo'5 days after full bloom (DAFB), when fruit growth rate increased sharply; and

Previous studies, in which the role of phosphorus in abscission of olive leaves was examined in the presence of ethylene biosynthesis inhibitors, have suggested that phosphorus induces abscission directly, without involvement of ethylene. In the present study, this possibility was further explored by comparing the effects of an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), and an ethylene action inhibitor, 2,5-norbornadiene (NBD), in olive [Olea europaea (L) cv. Manzanillo] and citrus [Citrus sinensis (L.) Osbeck cv. Shamouti]. In olive, leaf abscission was always induced in the presence of KH2PO4, with or without AVG and NBD (alone or in combination), but was more pronounced when KH2PO4 was applied alone. In citrus, the effect of KH2PO4 alone on the induction of leaf abscission and ethylene production was much stronger than that observed in olive. However, in the presence of NBD, KH2PO4 did not induce leaf abscission in citrus during the first 60 hr. Similar results were obtained when NBD was replaced by AVG, but, in this case, abscission was inhibited for only 48 hr. In both cases, ethylene was detected after the inhibitory period had ended. The results obtained with citrus indicate that the observed effect of KH2PO4 on the ethylene-independent induction of leaf abscission in olive is not a general phenomenon and may differ in different species.

Gibberellic acid reduces return bloom in many fruit tree species. Reducing bloom may cut costs of hand thinning apricot, peach and plum fruit. Sprays of 250 ppm GA, during floral bud evocation (June 1993) resulted in bud death and abscission as determined by light microscopy sections in `Patterson' apricot (Prunus armeniaca L). GA treatment in May did not cause observable effects. August treatments, immediately prior to floral initiation, did not impede differentiation. Treatment of `Elegant Lady' peach (Prunus persica [L.] Batsch.) buds with 75-250 ppm GA, in late June, 1993 (evocation phase) did not have any discernable effects in that season with respect to abscission or differentiation. Treated peach buds differentiated simultaneously with untreated buds in early August. The patterns of response to GA treatment imply `windows of opportunity' with respect to effectiveness of GA treatments. The specific response suggests that apricot buds possess differing levels of sensitivity to GA treatment and probably reflect distinct phases in transition to flowering. In August buds were already `determined' and were in a potentially floral state that was irreversible.

The addition of Al2O3 to 8-hydroxyquinoline citrate (8-HQC) solution did not alter the sensitivity of the leaf abscission zone to external ethylene treatment. Exogenous ethylene at 791 nl·l-1 for 72 to 120h and at 193 nl·l-1 for 120h induced leaf abscission whereas at 47 nl·l-1 for 72 to 120h no leaf abscission occurred. Ethylene treatment at 791 nl·l-1 for 72 to 120h increased ethylene evolution, but the amount of ethylene evolved from the explants does not seem to be enough for leaf abscission induction. Three different ethylene inhibitors, aminooxyacetic acid (AOA), CoCl2 and am inoethoxyvinylglycine (AVG), were used to determine whether phosphorus-induced leaf abscission was mediated through elevated ethylene evolution. Although AOA and CoCl2 failed to inhibit ethylene evolution from the explants stem-fed with NaH2P O4, AVG inhibited ethylene evolution. Each of the inhibitors except for 5 mM CoCl2 promoted leaf abscission when administered alone or with phosphorus. Our results reveal that phosphorus induced olive leaf abscission occurs without elevated ethylene evolution, but that oxygen is required.

Olive fruit harvest by mechanical shaking continues to be limited by poor fruit removal - less than 60% removal for most varieties. Whereas foliar spray of ethylene releasing compounds such as ethephon increases fruit removal percent, excessive leaf loss following treatment precludes commercial acceptance of the treatment. A classic case of serendipity has led to the testing of phosphorus as an olive fruit loosening agent. Na2 HPO4 at 25 mM applied via the cut stem of explants leads to massive leaf and fruit abscission. When the P source is applied at 100 mM foliar spray, fruit removal is accomplished with minimal leaf loss. Results of this investigation will cover P source, concentration, genera with abscission response and some indication of mechanism of action.

Trees that fruited during 1990 retained 67.3% of the inflorescence buds produced per branch in 1991 compared to 63.1% for trees that were defoliated immediately after harvest in 1990 and 21.3% by trees that were fruiting in 1991. Shading reduced bud retention similar to fruiting. Defoliation after nut harvest accentuated the delayed costs of reproduction caused by previous season's fruiting whereas shading produced significantly greater immediate costs. Shading effects on the allocation of carbon to buds, leaves and shoots were similar to those of fruiting. Leaf net photosynthesis under shade conditions was reduced to 14.27% of control trees and this led to a significant reduction in the relative growth rates of all the organs surveyed.

Record low temperatures were experienced in California during the last 10 days of December, 1990. Olive trees in both the Sacramento and San Joaquin Valleys suffered damage from the freeze. The lowest minimum recorded in these areas was -11.6C at Willows (Glenn Co.). Types of damage included death of succulent growing tips, defoliation, bark split, and bark and xylem discoloration. Tree death to the ground was uncommon. Defoliation continued throughout the growing season, and many leaves that persisted became chlorotic. Major outbreaks of olive knot disease caused by Pseudomonas savastanoi were seen in damaged trees, especially in `Manzanillo.' Anatomical studies showed evidence of ice nucleation events in the phloem, xylem, and leaves, but the cambium was usually left intact. Refoliation and healing of bark splits progressed rapidly once growth resumed in the spring, except in cases of olive knot infestation. Cultural practices that predisposed trees to freeze damage were those leading to late-season vegetative growth, namely fall pruning and late or excessive irrigation or fertilization. `Manzanillo' is the least cold-hardy of California cultivars and the most susceptible to olive knot. `Barouni' is the most hardy.

Xenia and metaxenia are phenomena dealing with the effects that pollen from different sources have on certain characteristics exhibited by seeds and fruits in a variety of species. A review of dictionaries, textbooks, and the scientific literature reveals that there is widespread confusion with regard to the nature of these phenomena and how they are to be distinguished. This discussion will attempt to clarify the boundary between these related phenomena by examining both the origins of the terms and our present understanding of the metabolism and anatomy involved. From this perspective, we contend that xenia applies to pollen effects as exhibited in the syngamous parts of ovules, that is, the embryo and endosperm only. Metaxenia applies to such effects found in any structure beyond the embryo and endosperm, this is, in tissues which derive wholly from mother plant material. Metaxenia then encompasses effects found in seed parts such as the nucellus and testa as well as those found in carpels and accessory tissue.

Photoperiod is an important environmental signal for regulating developmental patterns in many plant species. In several species, photoperiodic regulation of gibberellin A1 biosynthesis has been implicated as the mechanism by which photoperiod may alter development. To examine this phenomenon in strawberry, Fragaria virginiana plants grown under long day (LD) and short day (SD) conditions with equivalent total PAR were examined to determine changes in vegetative growth and GA1 biosynthesis.LD conditions (16 hr) promoted vegetative growth. Runner production, total leaf area, area of individual leaves, and petiole lengths, all increased under LD conditions. No runner production occurred under SD conditions (8 hr); however, the number of branch crowns increased.Gibberellins A44, A19, A20, and A1, all from the GA1 biosynthetic pathway, were identified in plants under both LD and SD conditions. However, SD conditions appeared to affect the 2β-hydroxylation of GA20 to GA1. Whereas levels of most GAs decreased under SD conditions, levels of GA20 increased, and only trace amounts of GA1 were found, indicating a possible blockage of the pathway at this point. As GA1 is considered the active component of the pathway, blockage of GA20 conversion under SD conditions may explain the concomitant reduction in vegetative growth.

Olive fruit persistence is a crucial component of yield and an important factor in estimating alternate bearing potential.Unfortunately, measurement of fruit persistence exhibit considerable variation, with coefficients of variation greater than 100. Such a high degree of variation makes field studies on questions regarding flowering and fruiting unmanageable due to the large number of experimental units necessary. To determine the source of this variation and how it might be reduced, comparisons of flower and fruit number per node were made within branches and trees over the course of two seasons. Results show that while the largest population of flowers are most distal on the branch, the central portion of the branch contains the majority of the final fruit population and has the lowest coefficient of variation. Furthermore, variation in the number of flowers and fruits is greater between branches than between nodes or trees. The implications of these data on experimental design are discussed and a design is proposed for reducing variation and labor needs.

Indole-3-acetic acid (IAA) has been implicated as a regulating agent in numerous plant-growth phenomena. In an attempt to assess its role in plants, identification and quantification are necessary. Estimating the amount of IAA in plant samples is difficult because this molecule degrades rapidly during most extraction-purification systems. A method is presented which reduces IAA degradation to a minimum by drying the sample at about 10-5 torr of oxygen and subsequently extracting with anhydrous solvent. A review of earlier methods is included.

Mist, low light, and low temperature during dormancy significantly promoted subsequent floral bud growth in peach (Prunus persica L. Batsch) while high temperature and high light intensity significantly decreased it. Chilling hours at 10°C bud temperature were half as effective as hours at 6°. No significant changes occurred in abscisic acid (ABA) levels in floral bud scales. ABA content of primordia within misted buds was significantly lower than of primordia in other treatments. The data support the concept that fog influences bud rest through temperature, light, and leaching effects. Results also indicate that ABA content in buds may not be the primary factor that determines termination of rest.

Ethylene evolution from leaves, stems, inflorescences and fruits of the olive plant (Olea europaea L.) cv. Manzanillo was studied at various stages of their development. Mature non-growing organs, particularly leaves, have a constant, low, and uniform rate of ethylene evolution. Ethylene evolution from detached mature olive leaves was constant during the first 12 h after excision. Leaves on shoots maintained in vitro kept a constant rate of ethylene evolution for at least the first 5–6 days. Leaf injury significantly increased ethylene evolution. Ethylene evolution from injured and non-injured control leaves could be markedly inhibited aminoethoxyvinylglycine (AVG) applied to the leaves or fed to the shoot. The use of excised olive shoots and leaves as an in vitro model system for studies of induced metabolic processes such as abscission and developing water stress was suggested.

None of the physiological events in plant growth and development is truly independent. Photosynthesis, flowering, and mineral transport are sharply focused areas of research; yet these phenomena are not separable from other metabolic events in the plant. This feature of interdependence may be called correlations (26) or growth correlations (49, 50). The control exerted by the growth zone emanates from a meristem; these meristems include the root or shoot apex, cambium, flowers, fruit, pollen on stigma, and the ovule or seed in a fruit.

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).

Analysis for hormones in plant material received impetus from the early studies of Went (4). Since that time, scientists have used living plant materials to estimate the presence of specific hormones. Among the advantages of the bioassay are sensitivity to the nanogram and in some cases, picogram range, ease of use, functionality with high levels of contaminants, and low cost of operation. The disadvantages include lack of specificity, variable response, and, in most instances, the need to use a species foreign to the one under examination.

Various treatments to remove the seed coat surgically revealed its role in preventing germination of non-stratified peach seed. The peach embryo from a non-chilled seed is not dormant, as it germinates readily when the seed coat is completely removed. The peach seed coat provides a physical impediment — commonly referred to as mechanical resistance to germination. Incision through the seed coat around the seed at the cotyledonary gap allowed germination even though the seed coat remained in contact with the embryo. No role for inhibitors extracted from the seed coat could be elucidated.

A series of experiments were performed to determine the role of the seed and crop load on flower induction in olive. Complete de-fruiting of branches 2–3 cm in diameter as early as 2 weeks after anthesis did not promote flowering in ‘Manzanillo’. Destruction of the seed promoted flower formation compared to seeded controls in both ‘Manzanillo’ and ‘Koroneiki’. Dry matter accumulation and partitioning in both seeded and seed-killed fruit were similar. Carbohydrate demand did not appear to be a primary factor in flower formation. Flowering was promoted in both varieties when the seed was destroyed prior to endocarp sclerification.

In a study of the purity and stability of 1,2-14C(2-chloroethyl)phosphonic acid when used as a radioactive tracer, 3 out of 4 radioactive impurities detected were found in all standards tested. In addition, 7 other non-radioactive compounds were found in 1 of the 14C-CEPA standards. One contaminant was found to be in equilibrium with the 14C-CEPA. No contaminants were detected on GLC of the non-radioactive CEPA standard. 14C-CEPA was non-enzymatically bound to some constituents in extracts of peach fruits, cv. Halford, particularly to sugars.

Seeds of ‘Nemaguard’ and ‘Halford’ peaches were chilled and removed periodically for chemical treatment, estimation of abscisic acid and gibberellic acid and assessment of germination response. Non-chilled ‘Nemaguard’ seed treated with gibberellin germinated at 80%, and after 2 weeks' chilling at nearly 100%. ‘Halford’ seed germination was not enhanced by gibberellin at any stage prior to or during chilling. Only ‘Nemaguard’ seed germination was hastened by benzylamino purine. Both ‘Nemaguard’ and ‘Halford’ seed germination was reduced by abscisic acid. ‘Halford’ was far more sensitive to 100 mg l−1 abscisic acid, with zero germination even after 8 weeks' chilling; a similar treatment for ‘Nemaguard’ resulted in 70% germination. ‘Nemaguard’ seedling growth following giberellin treatment of non-chilled seed was similar to chilled controls; in contrast, ‘Halford’ seedlings grown from seed so treated did not compare favorably with controls. Abscisic acid seed treatment prior to germination restricted ‘Nemaguard’ seedling growth after germination and prevented ‘Halford’ seedling growth. There remains no clear primary role for these hormones applied exogenously, or their endogenous content, in regulating peach seed dormancy. We suggest their role, if any, to be in seedling growth subsequent to germination.

A method was devised for quantitation of methylated indoleacetic (MeIAA) using a nitrogen-phosphorus (N-P) detector gas chromatograph with sensitivity greater than 5 pg MeIAA. Parameters are described for use conditions of the N-P detector.

Tree cages were used to modify temperature around ‘Starking Delicious’ apple (Malus domestica Borkh.) trees and to establish 4 bloom dates: April 2, 15 and May 7, 22. Determination of soluble solids, acid, firmness and chlorophyll indicated that the time from bloom to maturity was longer for fruit from earlier than normal bloom. Fruit from delayed bloom accumulated less soluble solids than that from normal or earlier bloom dates. Ultimate fruit size decreased with each successive bloom. Fruit from the 2 early bloom dates apparently was harvested before the preclimacteric minimum. Fruit from delayed bloom was harvested after initiation of the climacteric. Loss of fruit firmness in storage increased with successive harvests. Storage scald and green fruit color were associated with warm night temperatures just before harvest rather than with length of growing season.

Large differences in abscisic acid (ABA) concentrations were found among persisting fruit of ‘Winter Nelis’, seeded ‘Bartlett’ and parthenocarpic ‘Bartlett’ pear (Pyrus communis L.) even though fruit set and fruit growth rates were similar. Concentration of ABA was positively correlated with rate of fruit and seed growth in these 3 pear types. The concentration of ABA was greater in the seed than in fruit flesh, and in the integuments plus endosperm than in the embryo.

The identity of abscisic acid glucose ester, indole acetic acid, zeatin, and its riboside in pear receptacles was revealed by use of chromatographic, ultraviolet and mass spectral analysis.

In a 16-year field study, all graft combinations of Persian walnut, Juglans regia scions with other rootstock species were susceptible to blackline. ‘Sinensis #5’, a selection of J. regia, did not exhibit symptoms of blackline when used as an interstock. In no case was blackline observed in graft combinations between J. regia.

Fruit-bearing olive (Olea europaea L.) shoots were exposed to more than 100 ethylene (C2H4) treatments to determine if C2H4-induced abscission varied between leaves and fruits in response to manipulation of treatment concentration, duration, and total amount of exogenous C2H4. Nearly three-quarters of the treatments induced greater fruit abscission than leaf abscission on a percentage basis. The potential for optimization of C2H4-induced fruit abscission relative to leaf abscission was examined by calculating the fruit-to-Ieaf (F:L) abscission ratio. Of the treatments inducing at least 75% fruit abscission, the dose range of 150 to 370 μmol C2H4 gave ratios up to 13.3; however, results were highly variable and closely dependent on the interaction of concentration and duration. Response surfaces were created to depict this interaction. Desirable levels of fruit abscission occurred at durations > 30 hr and concentrations > 2 to 3 μl·liter−1. However, excessive leaf abscission occurred at durations of 24 to 48 hr, depending on concentration. Acceptable F:L ratios were found for about 30% of the surface, with the highest ratios occurring for treatments of 3 to 5 μl·liter−1 for 28 to 34 hr.