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Open access

Gonzalo F. Gil, George C. Martin, and William H. Griggs

Abstract

Seasonal changes in natural growth substances were studied by collecting the diffusate, via the pedicel, from intact seeded ‘Winter Nelis’, seeded ‘Bartlett’, and parthenocarpic ‘Bartlett’ pear fruits. The diffusate of ‘Bartlett’ fruits collected 10 to 25 days after full bloom (AFB) contained more auxin-like promoter than did that of ‘Winter Nelis’ fruits. With the exception of the 45-day sample, the diffusate from parthenocarpic ‘Bartlett’ fruits had more promoter from 25 to 70 days (AFB) than did either seeded pear. In contrast, more gibberellin (GA)-like materials diffused from ‘Winter Nelis’ fruits than from seeded or parthenocarpic ‘Bartlett’ fruits. With all types of pears the concentration of abscisic acid-like materials in the diffusate was similar until harvest when the concentration was greater for ‘Winter Nelis’ than for ‘Bartlett’. The combined effect of relatively low amounts of auxin-like and greater amounts of GA-like materials may explain why the presence of seeded pears during the postbloom period has a greater inhibitory effect on flower bud formation in ‘Winter Nelis’ than in ‘Bartlett’.

Open access

J. M. Kinet, D. Hurdebise, A. Parmentier, and R. Stainier

Abstract

The development of the inflorescence of tomato (Lycopersicon esculentum Mill.) plants grown in adverse light conditions was stimulated by exogenous applications of benzyladenine (BA) and gibberellin (GA) directly on the inflorescence. These two compounds had sequential effect in regulating the development of the inflorescence, the action of BA being exerted first and that of GA only subsequent to BA action. In combination with BA, GA4+7 was more effective than GA3 in promoting the development of the inflorescence. Determinations of carbohydrate contents in the inflorescences showed that during the treatment period with the growth substances, the soluble sugars and starch levels increased temporarily. Studies on the partitioning of the dry matter between the different plant portions suggested that the growth substances modified the distribution pattern of the assimilates within the plant; the inflorescence being favored at the expense of the young leaves above.

Open access

Kimani Waithaka, B. Esther Struckmeyer, and Malcolm N. Dana

Abstract

A foliar spray of 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA) induced thickening and restricted elongation of strawberry (Fragaria × ananassa Duch.) petioles and stolon internodes. Leaf area of treated plants was lower than that of untreated plants. Stolon internodes of treated plants increased in cell size and number. Gibberellic acid (GA3) promoted leaf expansion and elongation of petioles and stolon internodes. A combination of PBA and GA3 induced less thickening and more elongation of petioles and stolon internodes and greater leaf area compared to treatment with PBA alone. There was a breakdown of cell walls of pith parenchyma in stolon internodes of untreated plants while the cell walls of PBA and GA3 treated plants remained intact.

Open access

Kimani Waithaka and Malcolm N. Dana

Abstract

6-(Benzylamino)-9-(2-tetrahydrophyranyl)-9H-purine (PBA) promoted production of stolons, branch stolons, branch crowns and daughter plants in ‘Sparkle’ Junebearing and ‘Ozark Beauty’ everbearing strawberries (Fragaria × ananassa Duch.). Gibberellic acid (GA3) induced no promotion on either cultivar. Combinations of PBA and GA3 induced a greater effect on stolon and daughter plant production for ‘Ozark Beauty’ than did PBA alone. Increase in the number of daughter plants was proportional to the number of stolons produced. PBA suppressed rooting of the daughter plants. Addition of GA3 to the foliar treatment did not overcome rooting suppression of PBA.

Free access

Wen-Shaw Chen

The changes in cytokinins and gibberellins in xylem sap of lychee (Litchi chinensis Sonn. cv. Heh yeh) trees were investigated at the stages of leaf expansion, dormant bud (when apical leaves are dropped), 30 days before flower bud formation, flower bud formation, and full bloom of grafted field-grown lychee trees. Also; the diffusible IAA and ABA in diffusate from shoot tips were examined at the successive stages of development. High gibberellin was found in the xylem sap at the stage of leaf expansion. A constant level of IAA was maintained through the five growth stages. At 30 days before flower bud formation, ABA increased dramatically. Concurrently, total cytokinin content increased in the xylem sap, reaching a maximum during flower bud formation and full bloom. Gibberellin content in the xylem sap was at a low level 30 days before flower bud formation and through the stage of flower bud formation.

Free access

Yin-Tung Wang

Foliar application of 500 or 1000 mg BA or PBA/liter to stock plants of golden pothos [Epipremnum aureum (Linden & Andre) Bunt.] induced axillary bud elongation but did not promote growth of cuttings taken from these stock plants. Cuttings from plants treated with BA + GA4+7, each at 1000 mg·liter-1, died. Plants grown under 1000 μmol·s-1·m-2 had more but smaller leaves than those under 420 μmol·s-1·m-2. Cuttings produced under the higher light level grew more rapidly. Leaf area increased while stem length decreased as Osmocote slow-release fertilizer (18N-2.6P-10K) increased from 4 to 16 kg·m-3. A 24N-3.5P-13.3K water-soluble fertilizer applied at the rate of 0.42 g/500 ml weekly produced the best plants and resulted in the best cutting growth. Cuttings taken from stock plants receiving Osmocote at 4 kg·m-3 grew slower than those produced at other rates. Placement of cuttings in a mist-propagation bed for 1 or more weeks resulted in an accelerated growth rate relative to nonmisted cuttings. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (1α,2β,4aα,10β) 2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid l,-4a-lactone (GA4+7).

Open access

T. L. Gilbertson-Ferriss, M. L. Brenner, and H. F. Wilkins

Abstract

Corms of Freesia hybrida Bailey ‘Moya’ and F. hybrida ‘Maria’ were stored at 2°, 13°, or 30°C immediately after harvest and sampled at 0, 6, or 13 weeks for fresh weight, sprouting ability, free indoleacetic acid (IAA), free abscisic acid (ABA) and conjugated ABA (conj-ABA). High performance liquid and gas-liquid chromatography methods were used for identification and quantification of the extractable IAA, ABA, and conj-ABA. Shoots from corms planted immediately after harvest emerged in 33 to 57 days. It is suggested that freshly harvested F. hybrida corms exhibit physiological dormancy for not more than 4 to 6 weeks and subsequently enter a state of imposed dormancy in storage at 30° or 2°. Physiological dormancy was released more rapidly and corm shoots emerged more rapidly during imposed dormancy when stored at 30° versus 2°. The 30° treatment did not appear to be mandatory for shoot emergence since corms stored at 2° or 13° for 6 weeks emerged within 5 or 20 days, respectively. Extended storage at 13° promoted pupation whereas storage at 30° and 2° prevented pupation. Pupated corms did not emerge when planted. The IAA, ABA, and conj-ABA levels in the corms during storage did not correspond with growth inhibition but rather appeared to relate to the formation of the new corm during pupation.

Open access

I. C. Porlingis and D. Voyiatzis

Abstract

6-Benzylamino purine (BA) solutions at 100, 200 or 400 ppm, applied to self-pollinated flowers of the partly self-incompatible olive (Olea europaea, L. cv. Chalkidikis) at full bloom, increased the set of normal seeded fruits in young potted trees, in the greenhouse. In mature orchard trees, only concentrations at 400, 600 or 800 ppm were effective. Applications of BA to open-pollinated flowers failed to increase fruit-set. BA applied to unpollinated flowers did not induce the formation of normal fruits and did not increase the number or size of smaller parthenocarpic fruits. The use of 2-naphthoxyacetic acid (2-NOA) and potassiumgibberellate (KGA3), after self-pollination of the flowers, did not affect the set of normal seeded fruits.

Open access

Wen-Shaw Chen

Abstract

Changes in gibberellin and cytokinin activities were investigated at the stages of leaf differentiation, mature green leaves, early flower bud formation (7 days after formation), and full bloom of 3-year-old mangos (Mangifera indica L.) in pot culture. Also, diffusible IAA and ABA in the diffusate of shoot tips were examined at the different developing stages. High gibberellin and diffusable IAA activity was found in the xylem sap at leaf differentiation. Diffusible IAA decreased to a low level in shoot tip diffusates, and ABA increased dramatically during early flower bud formation. At the same time, total cytokinin-like activity increased in the xylem sap, reaching a maximum level at full bloom. Chemical names used: 1H-indole-3-acetic acid (IAA); [S-(Z,E)]-5-(l-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2,4-pentadienoic acid [abscisic acid (ABA)].

Open access

Daniel H. Diaz and George C. Martin

Abstract

An inhibitor was present in both seed coat and embryo of a high and a low chilling cv. of unstratified peach seeds and its concn decreased as stratification proceeded, Embryonic tissue retained more of the inhibitor than the seed coat. As the concn of inhibitor decreased, seed germination increased. The inhibitor was tentatively identified as abscisic acid (ABA) by chromatography. A bound inhibitor was also present in the seed parts of both cvs., and its concn increased in the embryo as stratification proceeded. More ABA and bound inhibitor were present in the high-chilling cv. than in the low-chilling counterpart, indicating that they may be related as factors which cause a cv. to require long periods of chilling. Application of ABA reduced germination percentage on stratified seeds without seed coats. Application of gibberellic acid (GA) and N-benzyladenine (BA) combined had a synergistic effect in promoting germination of dormant seeds.