**7. Fruit colour**

Application of paclobutrazol @ 0.33, 0.50, 0.66 and 1.32 g a.i. as soil application to 'Flavorcrest' peach hastened the fruit colour than control [47]. Looney and Mckeller [29] reported that paclobutrazol either sprayed once with 1000 ppm or twice with 500 ppm concentration to 'Lambert' cherry displayed less red colour as indicated by juice anthocyanin concentration or by visual rating of skin colour and 500 mg l<sup>−</sup><sup>1</sup> paclobutrazol within 5 weeks after full bloom to 'Mclntosh' apples gave high percentage of fruit with acceptable red colour at harvest [74]. Santa Rosa plum trees treated with 500 ppm paclobutrazol once at full bloom and repeated at pit hardening stage recorded maximum anthocyanin content (0.299 OD units) which was significantly higher than control [50]. Wani [37] observed that fruit colour was enhanced by the application of paclobutrazol in sweet cherry. Continuous application of paclobutrazol significantly reduces vegetative growth characters of the trees, thereby exposing fruits to direct sunlight which significantly increased red colouration of the fruits. The soil application of paclobutrazol in 'Red Delicious' apple fruits increased the fruit anthocyanin by the increasing dose of paclobutrazol [64].

#### **8. Fruit chemical characteristics**

Jindal and Chandel [50] observed that application of 500 ppm paclobutrazol to Santa Rosa plum in two successive years increased total sugars significantly from 5.46 to 6.71% in first year and 6.18 to 7.15% in next year. Similarly, reducing sugars

**51**

*Response of Growth Inhibitor Paclobutrazol in Fruit Crops*

also increased to 4.76 and 5.25% respectively, which was significantly higher than control and recorded an average of 3.94 and 4.50% reducing sugars. Also, least acid contents of 2.14 and 3.35% were observed than control which recorded average acid content of 2.45 and 3.13%, respectively. Wani [37] reported that fruit acidity, vitamin C, percentage of bruised fruits, incidence of pitting and fruit cracking were reduced by the application of paclobutrazol in sweet cherry. Also, the organoleptic rating, total soluble solids, reducing sugars, total sugars and anthocyanin were increased. Wani et al. [64] observed that the soil application of paclobutrazol decreased the acidity and ascorbic acid of 'Red Delicious' apple fruits. Also, the fruit total soluble solids, organoleptic rating and fruit calcium was increased by the increasing dose of paclobutrazol. Similar findings were noticed by Sarker et al. [75] in mango. Paclobutrazol application reduced the number of shoots, transforming trees into a more desirable, spur type growth habit and as the vegetative sink was reduced, transport of nutrients including calcium towards fruits was enhanced [72]. Higher uptake of Ca and its relocation to fruits could be attributed to significantly reduced rate of leaf transpiration, thus could favour the supply of Ca towards the fruit [76]. Fruit calcium is increased for 2–3 years due to carry over effect. Andres et al. [77] observed that the acidity content of fruits diminished as a result of the ripening process and the mango fruits treated with paclobutrazol and KNO3 showed the lowest values for acidity. Ashraf et al. [78] reported that with increase in paclobutrazol concentration and pruning levels, an increase in TSS, TSS/acid ratio, anthocyanin, sugars, fruit calcium and improvement in fruit grade was observed with decrease in fruit acidity in Red Delicious apples. This increased total soluble solids was due to increased sucrose, starch and sugar levels due to reduced vegetative growth and thus the absence of other potentially competitive actively growing sinks which resulted in more nutrient partitioning to fruits [54]. The increased rate of photosynthesis led by more light penetration into the interior tree canopy, increased the soluble solids in fruits harvested from pruned trees. These findings

are in conformity with the findings of Kumar et al. [61] in mango.

et al. [74] reported that foliar application of 500 mg l<sup>−</sup><sup>1</sup>

Wolstenholme et al. [49] reported that the application of paclobutrazol increased the partitioning of nutrients and dry matter towards fruits and thereby, increased the fruit size and weight. This increase in weight reduced the physiological loss in weight of fruits during storage period. The differences in storage performance may be due to ethylene production, responsible for the changes in texture and firmness and fruit softening [79]. Elfving et al. [80] observed that the fruits of McIntosh apple treated with diaminozide and paclobutrazol and stored for 24 weeks were firmer and displayed less core browning than untreated ones. Elfving

apples reduced flesh firmness loss and reduced post storage ethylene production in one season. Later applications at 5 and 9 weeks after full bloom affected stem cavity browning with increase in brown core. This may be attributed to reduction in ethylene evolution during storage which induced delay in respiratory climacteric after harvest and storage thereby, the loss in firmness was decreased [81]. The fruit flesh was firm due to retardation in ripening. Several physiological disorders and diseases of apple fruit during storage are related to the calcium content of fruit [82]. Calcium deficiency results in economic losses in fruit. It helps in regulation of metabolism in apple fruit and adequate concentrations maintain fruit flesh firmness and minimise the incidence of physiological disorders like water core, bitter pit and internal breakdown [83]. The increase in calcium generally delays the ripening

paclobutrazol in McIntosh

**9. Fruit storage behaviour**

*DOI: http://dx.doi.org/10.5772/intechopen.92883*

#### *Response of Growth Inhibitor Paclobutrazol in Fruit Crops DOI: http://dx.doi.org/10.5772/intechopen.92883*

Prunus

(188.12 cm3

**7. Fruit colour**

500 mg l<sup>−</sup><sup>1</sup>

total soluble solids (14.47o

**8. Fruit chemical characteristics**

in 'Santa Rosa' plum at 125, 250 and 500 ppm once at full bloom and again at pit hardening stage and reported maximum fruit weight of 24.33 g and fruit volume of 21.6 cc in fruits treated with 500 ppm of paclobutrazol. In persimmons, soil drench application of paclobutrazol accelerated ripening by 2–3 weeks [69]. The increase in fruit length and breadth was due to the reason that application of paclobutrazol reduced vegetative growth (sinks) which in turn, increased the partitioning of nutrients and dry matter towards fruits and thereby, increased the fruit size and weight [49]. Greene [72] reported that foliar application of paclobutrazol to Delicious apples produced fruits with higher flesh and less bitter pit, cork spot and senescence breakdown. Wani [37] reported that fruit acidity, vitamin C, percentage of bruised fruits, incidence of pitting and fruit cracking were reduced by the application of paclobutrazol in sweet cherry. Also, the organoleptic rating, total soluble solids, reducing sugars, total sugars and anthocyanin were increased. Pant and Ratan [36] studied the influence of different concentrations of paclobutrazol and chloromequat at 250, 500, 1000 and 5000 ppm on quality of apple cv. Red Delicious and observed that fruit weight and firmness was increased with both growth retardants. In contrast, in strawberries paclobutrazol application rate had no significant effect on fruit firmness [73]. Carreno et al. [58] found that grape berry size increased linearly with an increase in paclobutrazol application rate. Ashraf et al. [43, 44] observed that treatment 750 ppm paclobutrazol +2 summer prunings resulted in significantly improved fruit size (53.15 cm), weight (188.19 g), volume

), colour change (3.40 score), firmness (11.98 kg cm<sup>−</sup><sup>2</sup>

rating in terms of taste (3.14 score), texture (3.24 score), flavour (3.12 score) and

control and other treatments during both the years in apple cv. Red Delicious. The improvement in organoleptic rating of fruits may be attributed to the fact that more metabolites were translocated to the fruits in treated trees with paclobutrazol.

Application of paclobutrazol @ 0.33, 0.50, 0.66 and 1.32 g a.i. as soil application to 'Flavorcrest' peach hastened the fruit colour than control [47]. Looney and Mckeller [29] reported that paclobutrazol either sprayed once with 1000 ppm or twice with 500 ppm concentration to 'Lambert' cherry displayed less red colour as indicated by juice anthocyanin concentration or by visual rating of skin colour and

high percentage of fruit with acceptable red colour at harvest [74]. Santa Rosa plum trees treated with 500 ppm paclobutrazol once at full bloom and repeated at pit hardening stage recorded maximum anthocyanin content (0.299 OD units) which was significantly higher than control [50]. Wani [37] observed that fruit colour was enhanced by the application of paclobutrazol in sweet cherry. Continuous application of paclobutrazol significantly reduces vegetative growth characters of the trees, thereby exposing fruits to direct sunlight which significantly increased red colouration of the fruits. The soil application of paclobutrazol in 'Red Delicious' apple fruits increased the fruit anthocyanin by the increasing dose of paclobutrazol [64].

Jindal and Chandel [50] observed that application of 500 ppm paclobutrazol to Santa Rosa plum in two successive years increased total sugars significantly from 5.46 to 6.71% in first year and 6.18 to 7.15% in next year. Similarly, reducing sugars

paclobutrazol within 5 weeks after full bloom to 'Mclntosh' apples gave

B) whereas acidity (0.23%) was reduced in comparison to

), organoleptic

**50**

also increased to 4.76 and 5.25% respectively, which was significantly higher than control and recorded an average of 3.94 and 4.50% reducing sugars. Also, least acid contents of 2.14 and 3.35% were observed than control which recorded average acid content of 2.45 and 3.13%, respectively. Wani [37] reported that fruit acidity, vitamin C, percentage of bruised fruits, incidence of pitting and fruit cracking were reduced by the application of paclobutrazol in sweet cherry. Also, the organoleptic rating, total soluble solids, reducing sugars, total sugars and anthocyanin were increased. Wani et al. [64] observed that the soil application of paclobutrazol decreased the acidity and ascorbic acid of 'Red Delicious' apple fruits. Also, the fruit total soluble solids, organoleptic rating and fruit calcium was increased by the increasing dose of paclobutrazol. Similar findings were noticed by Sarker et al. [75] in mango. Paclobutrazol application reduced the number of shoots, transforming trees into a more desirable, spur type growth habit and as the vegetative sink was reduced, transport of nutrients including calcium towards fruits was enhanced [72]. Higher uptake of Ca and its relocation to fruits could be attributed to significantly reduced rate of leaf transpiration, thus could favour the supply of Ca towards the fruit [76]. Fruit calcium is increased for 2–3 years due to carry over effect. Andres et al. [77] observed that the acidity content of fruits diminished as a result of the ripening process and the mango fruits treated with paclobutrazol and KNO3 showed the lowest values for acidity. Ashraf et al. [78] reported that with increase in paclobutrazol concentration and pruning levels, an increase in TSS, TSS/acid ratio, anthocyanin, sugars, fruit calcium and improvement in fruit grade was observed with decrease in fruit acidity in Red Delicious apples. This increased total soluble solids was due to increased sucrose, starch and sugar levels due to reduced vegetative growth and thus the absence of other potentially competitive actively growing sinks which resulted in more nutrient partitioning to fruits [54]. The increased rate of photosynthesis led by more light penetration into the interior tree canopy, increased the soluble solids in fruits harvested from pruned trees. These findings are in conformity with the findings of Kumar et al. [61] in mango.

### **9. Fruit storage behaviour**

Wolstenholme et al. [49] reported that the application of paclobutrazol increased the partitioning of nutrients and dry matter towards fruits and thereby, increased the fruit size and weight. This increase in weight reduced the physiological loss in weight of fruits during storage period. The differences in storage performance may be due to ethylene production, responsible for the changes in texture and firmness and fruit softening [79]. Elfving et al. [80] observed that the fruits of McIntosh apple treated with diaminozide and paclobutrazol and stored for 24 weeks were firmer and displayed less core browning than untreated ones. Elfving et al. [74] reported that foliar application of 500 mg l<sup>−</sup><sup>1</sup> paclobutrazol in McIntosh apples reduced flesh firmness loss and reduced post storage ethylene production in one season. Later applications at 5 and 9 weeks after full bloom affected stem cavity browning with increase in brown core. This may be attributed to reduction in ethylene evolution during storage which induced delay in respiratory climacteric after harvest and storage thereby, the loss in firmness was decreased [81]. The fruit flesh was firm due to retardation in ripening. Several physiological disorders and diseases of apple fruit during storage are related to the calcium content of fruit [82]. Calcium deficiency results in economic losses in fruit. It helps in regulation of metabolism in apple fruit and adequate concentrations maintain fruit flesh firmness and minimise the incidence of physiological disorders like water core, bitter pit and internal breakdown [83]. The increase in calcium generally delays the ripening

of the fruit and maintains their quality during prolonged storage. Fruit calcium is increased for 2–3 years due to carry over effect by paclobutrazol application. This increase in fruit calcium reduced bitter pit, cork spot, senescent breakdown so, spoilage of fruits was reduced which in turn enhanced storage life of fruits [17]. Our findings are in conformity with the findings of Wani [37] in sweet cherry and Wani et al. [64] in 'Red Delicious' apple. Paclobutrazol application reduced the number of shoots, transforming trees into a more desirable, spur type growth habit and as the vegetative sink was reduced, transport of nutrients including calcium towards fruits was enhanced.

### **10. Nutrient uptake**

Paclobutrazol application influences the leaf nutrient status of various temperate fruit crops:

**Nitrogen:** Paclobutrazol application reduced foliar N concentration in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. However, Sharma and Joolka [40] recorded reduced leaf N content with paclobutrazol in nonpareil almond plants.

**Phosphorus:** Paclobutrazol application reduced foliar P concentration in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. Increased foliar P concentration in apple plants treated with PP333 has been reported by Curry [88]. However, Sharma and Joolka [40] recorded reduced leaf P content with paclobutrazol in nonpareil almond plants.

**Potassium:** Paclobutrazol application reduced foliar K contents in Nemaguard [84], Flordaprince peach [85], stone fruits [89], Red Spur Delicious and Vance Delicious [87]. Contrary to this, Swietlik and Miller [90] observed increase in K uptake with the addition of 0.2 ppm PP333 to a nutrient solution in which 11 month old apple seedlings were grown. However, Sharma and Joolka [40] recorded reduced leaf K content with paclobutrazol in nonpareil almond plants.

**Calcium:** Increased concentration of foliar Ca with paclobutrazol application was observed in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. Similar observations regarding the increase in foliar Ca concentrations in various apple cultivars were made by Bonomo et al. [91]. Swietlik and Miller [92] further reported that Ca content in Golden Delicious increased in proportion to the increasing doses of PP333. Sharma and Joolka [40] also recorded increased leaf Ca content with paclobutrazol in nonpareil almond plants.

**Magnesium:** Foliar Mg content has been reported to increase with paclobutrazol application in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86], Red Spur Delicious and Vance Delicious apples [87] and apple plants [91]. But Curry [88] found reduced levels of foliar Mg in apple plants treated with PP333. However, Sharma and Joolka [40] also recorded increased leaf Mg content with paclobutrazol in nonpareil almond plants.

#### **11. Conclusion**

Paclobutrazol (PP333) has been effectively used to manipulate tree vigour in several perennial fruit crops. Paclobutrazol application reduces the amount of pruning which requires skilled labour and is time consuming and costly.

**53**

**Author details**

\* and Moieza Ashraf<sup>2</sup>

Sciences and Technology of Kashmir, Srinagar, India

\*Address all correspondence to: naira.ashraf@gmail.com

Technology of Kashmir, Srinagar, India

provided the original work is properly cited.

1 Division of Fruit Science, Sher-e-Kashmir University of Agricultural Sciences and

2 Division of Environmental Science, Sher-e-Kashmir University of Agricultural

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Naira Ashraf1

*Response of Growth Inhibitor Paclobutrazol in Fruit Crops*

use hence such trees are suitable under drought conditions.

Paclobutrazol is effective not only in flower induction but also in early and off season flower induction which thereby maintains regularity and synchronisation in flowering. Paclobutrazol application affected fruit yield, quality characteristics and helps in maintenance of better fruit quality during storage. It influences the nutrient uptake in various fruit crops. Paclobutrazol was also shown to shift assimilate partitioning from leaves to roots, increase carbohydrates in all parts of fruit seedlings which enhances cold hardiness during winter periods. It increases chlorophyll content, soluble protein and mineral element concentration in leaf tissue which result in compact darker leaves. It also increases root respiration and reduce water

*DOI: http://dx.doi.org/10.5772/intechopen.92883*

#### *Response of Growth Inhibitor Paclobutrazol in Fruit Crops DOI: http://dx.doi.org/10.5772/intechopen.92883*

Prunus

was enhanced.

ate fruit crops:

almond plants.

zol in nonpareil almond plants.

**10. Nutrient uptake**

of the fruit and maintains their quality during prolonged storage. Fruit calcium is increased for 2–3 years due to carry over effect by paclobutrazol application. This increase in fruit calcium reduced bitter pit, cork spot, senescent breakdown so, spoilage of fruits was reduced which in turn enhanced storage life of fruits [17]. Our findings are in conformity with the findings of Wani [37] in sweet cherry and Wani et al. [64] in 'Red Delicious' apple. Paclobutrazol application reduced the number of shoots, transforming trees into a more desirable, spur type growth habit and as the vegetative sink was reduced, transport of nutrients including calcium towards fruits

Paclobutrazol application influences the leaf nutrient status of various temper-

**Nitrogen:** Paclobutrazol application reduced foliar N concentration in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. However, Sharma and Joolka [40] recorded reduced leaf N content with paclobutrazol in nonpareil

**Phosphorus:** Paclobutrazol application reduced foliar P concentration in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. Increased foliar P concentration in apple plants treated with PP333 has been reported by Curry [88]. However, Sharma and Joolka [40] recorded reduced leaf P content with paclobutra-

**Potassium:** Paclobutrazol application reduced foliar K contents in Nemaguard [84], Flordaprince peach [85], stone fruits [89], Red Spur Delicious and Vance Delicious [87]. Contrary to this, Swietlik and Miller [90] observed increase in K uptake with the addition of 0.2 ppm PP333 to a nutrient solution in which 11 month old apple seedlings were grown. However, Sharma and Joolka [40] recorded reduced

**Calcium:** Increased concentration of foliar Ca with paclobutrazol application was observed in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86] and Red Spur Delicious and Vance Delicious apples [87]. Similar observations regarding the increase in foliar Ca concentrations in various apple cultivars were made by Bonomo et al. [91]. Swietlik and Miller [92] further reported that Ca content in Golden Delicious increased in proportion to the increasing doses of PP333. Sharma and Joolka [40] also recorded increased leaf Ca content

**Magnesium:** Foliar Mg content has been reported to increase with paclobutrazol application in Nemaguard [84], Flordaprince [85], Flordaprince and Flordagold peach cultivars [86], Red Spur Delicious and Vance Delicious apples [87] and apple plants [91]. But Curry [88] found reduced levels of foliar Mg in apple plants treated with PP333. However, Sharma and Joolka [40] also recorded increased leaf Mg

Paclobutrazol (PP333) has been effectively used to manipulate tree vigour in several perennial fruit crops. Paclobutrazol application reduces the amount of pruning which requires skilled labour and is time consuming and costly.

leaf K content with paclobutrazol in nonpareil almond plants.

with paclobutrazol in nonpareil almond plants.

content with paclobutrazol in nonpareil almond plants.

**52**

**11. Conclusion**

Paclobutrazol is effective not only in flower induction but also in early and off season flower induction which thereby maintains regularity and synchronisation in flowering. Paclobutrazol application affected fruit yield, quality characteristics and helps in maintenance of better fruit quality during storage. It influences the nutrient uptake in various fruit crops. Paclobutrazol was also shown to shift assimilate partitioning from leaves to roots, increase carbohydrates in all parts of fruit seedlings which enhances cold hardiness during winter periods. It increases chlorophyll content, soluble protein and mineral element concentration in leaf tissue which result in compact darker leaves. It also increases root respiration and reduce water use hence such trees are suitable under drought conditions.
