Effect of Soil-Applied Paclobutrazol in Drip Irrigated Peach Orchards

Four concentrations of paclobutrazol (PBZ) and two application methods (foliar spray-soil drench) were tested on 3-month-old container-grown cork oak (Quercus suber L.) seedlings. Shoot height was affected by PBZ concentration and application technique. Time course of height was modelled by nonlinear mixed model analysis. Reduced shoot height was the result of shortened and fewer internodes. A 25 to 625 ppm soil drench or 625 to 15,000 ppm foliar spray controlled over vegetative growth, resulting in a reduction between 13% and 90% in plant size relative to untreated controls. Seedlings responded to soil drench at a lower PBZ concentration than for a foliar spray, but the danger of irreversible overdosing seems greater for a soil drench. Soil drench-and foliar spray to a lesser extent-also affected other shoot and root growth traits. PBZ dose decreased root volume and dry weights in a quadratic fashion with increasing dose, but decreased diameter and number of leaves linearly.

Section: Discussionmentioning

confidence: 97%

Growth of Container-grown Cork Oak Seedlings as Affected by Foliar and Soil Application of Paclobutrazol

Pardos¹,

Calama²,

Montero³

et al. 2005

“…Other pomologists have shown that foliar sprays and root-zone treatments with PBZ effectively suppress shoot growth of peach (Early and Martin, 1988;Erez, 1986;Williamson et al, 1986), and Casper and Taylor (1989) report that foliar-applied GA 3 will reverse the growth suppression caused by PBZ. Our results contribute to this body of knowledge by showing that: a) GA 3 can be introduced to peach trees via the root system; b) very low concentrations of PBZ (1 to 2 ppb) suppress shoot growth when applied via the nutrient solution (confirming a result previously reported by Early and Martin, 1988), but this effect is reversible across a range of RZTs by root-applied GA 3 ; and c) PBZ applied to the roots increases average root diameter, and even root volume at higher RZTs, but may not increase root dry weight relative to untreated plants.…”

mentioning

confidence: 99%

“…It is known that root-applied gibberellins are absorbed and transported throughout the plant (Davies and Rappaport, 1975) and that they promote shoot elongation of both herbaceous (Anderson et al, 1988;Arteca et al, 1985;Jackson and Field, 1972) and woody perennial plants (Heidmann, 1982;Little and Loach, 1975). It is also known that triazol growth inhibitors (e.g., PBZ and uniconazole) have the opposite effect on shoot growth (Early and Martin, 1988;Erez, 1986). However, there is only indirect evidence that root-zone temperature can influence these PGR effects (Lavender et al, 1973;Menhenett and Waring, 1975).…”

mentioning

confidence: 99%

Response of Peach Seedlings to Root-zone Temperature and Root-applied Growth Regulators

Tagliavini¹,

Looney²

1991

Root and shoot growth of peach seedlings was strongly suppressed when the roots were held at 8 to 10C. Shoot and root dry weights and root volume increased linearly with increasing root-zone temperature (RZT) to 22C. GA3 at 5.7 μm (2 ppm) added to the aerated full nutrient solution reversed the effect of low RZT on shoot elongation but inhibited root growth at all RZTs. Paclobutrazol (PBZ) (6.8 × 10-3μm) (2 ppb) inhibited shoot elongation at all RZTs and shoot dry weight at 16 and 22C. However, PBZ had no effect on root dry weight accumulation at any RZT. The shoot growth-promoting effect of GA3, relative to control plants, disappeared at higher RZTs, but GA3 reversed the growth-inhibiting effect of PBZ at all RZTs. PBZ increased mean root diameter at all RZTs and significantly increased root volume at 22C. These results show that growth of peach seedlings is profoundly influenced by a cool root-zone environment. The plant growth regulator effects suggest that seedling roots play an important role in whole-plant gibberellin physiology. Some possible implications for fruit production are discussed. Chemical names used: gibberellic acid (GA3); β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol(paclobutrazol,PBZ).

“…In various fruit species or cultivars, PBZ advances (Looney and McKellar, 1987;Marini, 1987;Proebsting and Mills, 1985;Webster et al, 1986) or delays (Curry, 1988;Erez, 1986;Porlingis and Voyiatzis, 1986;Spiers, 1988) anthesis. In cider apple (Malus domestica Borkh.…”

mentioning

confidence: 99%

Delaying Anthesis of Staminate Pistachio with Paclobutrazol

Porlingis¹,

Voyiatzis²

1993

Anthesis of an important staminate pistachio (Pistacia vera L.) cultivar (B) in Greece was delayed by foliar paclobutrazol (PBZ) sprays applied in June or July the previous season. A September spray was ineffective. The amount of delay depended on dose (50 to 1000 mg PBZ/liter applied to incipient runoff). Using the same total amount of chemical, one spray was as effective as two sprays 1 month apart. There were no effects on inflorescence fresh weight, pollen production, and pollen germination. Stem elongation was inhibited strongly, but the number of nodes and flower buds per shoot was reduced only slightly. In Expt. 2, two other staminate cultivars (A and C) responded similarly to cultivar B. Treatment effects appeared only during the treatment year, whereas a soil drench was effective for 2 years. PBZ may be able to synchronize the blooming of staminate and distillate pistachio cultivars and result in good fruit set without artificial pollination. Chemical name used: B[(4-chlorophenyl)methyl] -α-(1,1 dimethylethyl)-l H -1,2,4-triazole-l-ethanol (paclobutrazol).