Changes in Leaf Thickness, Chlorophyll Content, and Gas Exchange of a Landscape Tree, Xanthostemon chrysanthus, Treated with Paclobutrazol and Potassium Nitrate

Ahmad Nazarudin Mohd Roseli; Tsan Fui Ying; Normaniza Osman

doi:10.48044/jauf.2021.005

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Figure 1.
Xanthostemon chrysanthus planted by the roadside of Metropolitan Batu Park.
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Figure 2.
Comparison of leaf size and greenness in X. chrysanthus at 6 months after treatment with PBZ and KNO₃.
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Figure 3.
Micrographs of X. chrysanthus leaves at 6 months after treatment with PBZ and KNO₃. (a) Untreated control leaf; (b) KNO₃-treated leaf; (c) PBZ-treated leaf; (d) PBZ + KNO₃-treated leaf. Palisade parenchyma (P); Spongy parenchyma (S); Epidermis (E); Cuticle (C).

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Table 1.

Monthly changes in relative chlorophyll content of X. chrysanthus treated with PBZ and KNO₃.

Treatment combination							Relative chlorophyll content
PBZ (g L⁻¹)	KNO₃ (g)	Apr 2012	May 2012	Jun 2012	Jul 2012	Aug 2012	Sep 2012	Oct 2012	Nov 2012	Dec 2012	Jan 2013	Feb 2013	Mar 2013
0	0	41.93 ± 2.69 a	40.92 ± 2.55 b	41.20 ± 1.24 d	41.88 ± 2.41 d	41.21 ± 2.55 c	41.28 ± 1.98 b	41.23 ± 1.22 b	41.09 ± 2.62 b	40.14 ± 4.30 b	41.06 ± 1.69 b	39.48 ± 1.99 c	39.44 ± 2.05 b
0	100	42.34 ± 3.16 a	45.57 ± 3.21 a	48.32 ± 4.25 bc	52.24 ± 4.01 ab	50.21 ± 3.26 b	49.72 ± 3.81 a	48.61 ± 2.00 a	49.23 ± 3.69 a	48.97 ± 4.39 a	49.21 ± 5.26 a	48.28 ± 3.70 ab	49.70 ± 5.04 a
0	200	41.63 ± 3.25 a	45.92 ± 4.99 a	48.55 ± 5.48 bc	50.28 ± 5.14 bc	47.59 ± 3.47 b	47.48 ± 7.03 a	48.70 ± 5.77 a	47.53 ± 2.99 a	48.76 ± 4.73 a	46.72 ± 6.30 a	47.37 ± 4.73 ab	47.60 ± 3.11 a
0.125	0	40.86 ± 2.43 a	45.17 ± 3.85 a	49.82 ± 2.83 abc	49.88 ± 3.80 bc	49.74 ± 5.39 b	49.92 ± 4.72 a	48.62 ± 3.64 a	49.63 ± 3.82 a	51.44 ± 5.49 a	50.44 ± 3.01 a	48.54 ± 3.38 ab	47.92 ± 3.33 a
0.125	100	40.92 ± 2.50 a	47.22 ± 5.03 a	52.34 ± 3.43 ab	54.08 ± 4.48 ab	51.16 ± 5.03 ab	51.63 ± 4.64 a	53.06 ± 4.13 a	51.27 ± 3.94 a	52.82 ± 7.20 a	49.63 ± 4.90 a	50.58 ± 5.50 ab	48.96 ± 4.86 a
0.125	200	40.16 ± 2.47 a	46.91 ± 5.68 a	52.25 ± 4.37 ab	54.38 ± 3.56 ab	52.53 ± 5.78 ab	51.30 ± 3.36 a	51.12 ± 4.54 a	50.79 ± 6.37 a	48.89 ± 3.14 a	50.79 ± 6.79 a	50.38 ± 2.84 ab	50.21 ± 2.88 a
0.25	0	41.88 ± 1.82 a	46.81 ± 2.17 a	50.67 ± 4.15 abc	53.61 ± 3.09 ab	51.82 ± 3.31 ab	50.93 ± 5.20 a	51.29 ± 3.41 a	49.09 ± 3.50 a	51.78 ± 4.51 a	49.09 ± 4.71 a	50.26 ± 5.21 ab	49.02 ± 5.60 a
0.25	100	40.30 ± 2.90 a	46.78 ± 3.38 a	50.82 ± 4.31 abc	54.21 ± 3.47 ab	51.92 ± 5.55 ab	50.07 ± 2.81 a	52.09 ± 5.75 a	51.66 ± 6.00 a	51.71 ± 3.97 a	51.43 ± 4.40 a	49.63 ± 3.79 ab	50.32 ± 3.83 a
0.25	200	41.48 ± 3.49 a	45.71 ± 5.94 a	48.82 ± 4.46 abc	54.35 ± 4.65 ab	52.16 ± 5.25 ab	51.29 ± 6.47 a	49.86 ± 3.94 a	49.54 ± 2.84 a	51.60 ± 5.88 a	50.22 ± 4.76 a	51.58 ± 4.94 a	50.94 ± 5.09 a

Means followed by the same letter(s) within column do not differ by DMRT (2-way ANOVA, p < 0.05); Mean ± standard deviation; n = 27/treatment.

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Table 2.

Thickness increase of palisade and spongy parenchyma in X. chrysanthus at 6 months after treatment with PBZ and KNO₃.

Treatment combination		Palisade parenchyma thickness	Spongy parenchyma thickness
PBZ (g L⁻¹)	KNO₃ (g)	increase (%)	increase (%)
0	0	2.49	1.27
0	100	14.69	1.58
0	200	16.79	1.12
0.125	0	36.32	1.37
0.125	100	42.38	−0.74
0.125	200	44.43	−0.06
0.25	0	37.41	0.67
0.25	100	44.31	−1.02
0.25	200	51.12	−1.18

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Table 3.

Changes in leaf thickness of X. chrysanthus at 6 months after treatment with PBZ and KNO₃.

Treatment combination		Leaf thickness (μm)		Leaf thickness increase (%)
PBZ (g L⁻¹)	KNO₃ (g)	0 months after treatment	6 months after treatment	6 months after treatment
0	0	185.40 ± 9.69 a	187.08 ± 8.50 d	0.91
0	100	184.19 ± 6.26 a	193.21 ± 10.98 c	4.89
0	200	184.21 ± 8.20 a	193.18 ± 8.69 c	4.87
0.125	0	185.39 ± 5.65 a	203.77 ± 9.48 b	9.91
0.125	100	184.64 ± 3.91 a	206.90 ± 8.36 ab	12.06
0.125	200	185.41 ± 6.64 a	207.14 ± 8.85 ab	11.72
0.25	0	184.62 ± 6.34 a	203.44 ± 10.26 b	10.19
0.25	100	184.18 ± 4.78 a	206.84 ± 7.79 ab	12.30
0.25	200	185.44 ± 3.68 a	210.23 ± 7.11 a	13.37

Means followed by the same letter(s) within column do not differ by DMRT (2-way ANOVA, p < 0.05); Mean ± standard deviation; n = 45/treatment.

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Table 4.

Physiological response of X. chrysanthus at 6 and 12 months after treatment with PBZ and KNO₃.

Treatment combination		Photosynthetic rate (μmol m⁻²s⁻¹)		Transpiration rate (mmol m⁻²s⁻¹)		Stomatal conductance (mol m⁻²s⁻¹)
PBZ (g L⁻¹)	KNO₃ (g)	6 months after treatment	12 months after treatment	6 months after treatment	12 months after treatment	6 months after treatment	12 months after treatment
0	0	6.56 ± 1.07 a	6.02 ± 0.93 a	3.04 ± 0.80 a	2.72 ± 0.56 a	0.14 ± 0.03 a	0.14 ± 0.07 a
0	100	5.28 ± 0.60 b	5.40 ± 0.74 b	2.18 ± 0.59 b	1.90 ± 0.37 b	0.11 ± 0.08 a	0.12 ± 0.06 a
0	200	5.50 ± 0.69 b	5.07 ± 0.76 b	2.01 ± 0.53 b	1.95 ± 0.51 b	0.11 ± 0.08 a	0.11 ± 0.07 a
0.125	0	3.82 ± 0.61 cde	3.53 ± 0.63 c	0.78 ± 0.12 c	0.76 ± 0.14 c	0.05 ± 0.02 b	0.05 ± 0.02 b
0.125	100	3.86 ± 0.62 cd	3.58 ± 0.90 c	0.84 ± 0.11 c	0.76 ± 0.15 c	0.05 ± 0.02 b	0.03 ± 0.01 b
0.125	200	3.92 ± 0.93 cd	3.73 ± 0.93 c	0.77 ± 0.13 c	0.74 ± 0.16 c	0.04 ± 0.02 b	0.03 ± 0.01 b
0.25	0	3.25 ± 1.17 de	3.23 ± 0.82 c	0.76 ± 0.13 c	0.72 ± 0.14 c	0.05 ± 0.03 b	0.04 ± 0.03 b
0.25	100	3.55 ± 0.90 de	3.31 ± 0.55 c	0.76 ± 0.12 c	0.74 ± 0.13 c	0.02 ± 0.01 b	0.03 ± 0.01 b
0.25	200	3.42 ± 0.58 de	3.27 ± 0.38 c	0.75 ± 0.13 c	0.74 ± 0.11 c	0.02 ± 0.01 b	0.03 ± 0.02 b