Manihot leaf abscission induced by ethrel

This study aimed to assess the impact of ethrel spraying on cassava leaf abscission at different stages of cultivar development. Two experiments were performed using randomized block designs, with 15 total treatments (three repetitions of five conditions) arranged according to the factorial scheme 3 x 5. Experiment 1 (ethrel application in the vegetative development period) consisted of three seasons (November 2013 and 2014, January and February 2014) and four concentrations of ethrel (1,500, 3,000, 4,500, and 6,000 ppm) and a control (no application); Experiment 2 (application in pre-harvest period) consisted of three periods of ethrel spraying (20, 40, and 60 days before harvest), four ethrel concentrations (1,500, 3,000, 4,500, and 6,000 ppm) and a control (without ethrel). The characteristics evaluated included the number of fallen leaves at 20 and 70 days after application, total leaf dry mass and foliar degreening. The effects of different concentrations and times of application of ethrel were significant during the first seven days. Ethrel application during the second period of vegetative development did not affect the number of fallen leaves over a period of 70 days.

Keywords:
ManihotesculentaCrantz; leaf fall; plant growth regulator

Authorship

Carmem Lacerda Lemos Brito ^**Author for correspondence. E-mail: lemoscarmem@yahoo.com.br

Programa de Pós Graduação em Agronomia, Universidade Estadual do Sudoeste da Bahia, Estrada Bem Querer, 04, 45031-900, Vitória da Conquista, Bahia, Brazil. Universidade Estadual do Sudoeste da BahiaBrazilVitória da Conquista, Bahia, BrazilPrograma de Pós Graduação em Agronomia, Universidade Estadual do Sudoeste da Bahia, Estrada Bem Querer, 04, 45031-900, Vitória da Conquista, Bahia, Brazil.

Sylvana Naomi Matsumoto

Departamento de Fitotecnia e Zootecnia, Universidade Estadual do Sudoeste da Bahia, Vitória da Conquista, Bahia, Brazil. Universidade Estadual do Sudoeste da BahiaBrazilVitória da Conquista, Bahia, BrazilDepartamento de Fitotecnia e Zootecnia, Universidade Estadual do Sudoeste da Bahia, Vitória da Conquista, Bahia, Brazil.

Luan Santos de Oliveira

Programa de Pós Graduação em Agronomia, Faculdade de Ciências Agronômicas, Botucatu, São Paulo, Brazil.Faculdade de Ciências AgronômicasBrazilBotucatu, São Paulo, BrazilPrograma de Pós Graduação em Agronomia, Faculdade de Ciências Agronômicas, Botucatu, São Paulo, Brazil.

Gabriela Luz Pereira Moreira

Jerffson Lucas Santos

Anselmo Eloy Silveira Viana

*Author for correspondence. E-mail: lemoscarmem@yahoo.com.br

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables | Formulas

Figures (5)
Tables (1)
Formulas (1)

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Figure 1
Precipitation (mm), atmospheric relative humidity (%), and maximum and minimum monthly average temperatures (°C) of the periods January2013 - July 2014 (A) and January2014 - July2015 (B).

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Figure 2
Number of fallen leaves in the soil at 7 (LA7) and 70 days (LA70), and total leaf dry mass (LDM) according to application dates (A, C, and D) and ethrel concentrations (B, E, and F) in two culture cycles of Caitité variety cassava plants. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant difference by regression variance analysis at p ≤ 0.01% and p≤ 0.05, respectively.

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Figure 3
Abscission speed index at 70 days (ASI70) and at 20 days (AVI20) after ethrel spraying relative to application time (A and C) and ethrel concentration (B and D) during the two cultivation cycles of cassava plants of the Caitité variety. For each ethrel concentration, means followed by the same letter do not differ from each other by the Tukey’s test (p ≤ 0,05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

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Figure 4
Fallen leaf number at 7 (LA7) and 20 days after treatment (LA20), and total leaf dry mass 20 days after treatment in relation to the date of application and ethrel concentration (C. D and F) during the pre-harvesting period in two culture cycles of the Caitité variety cassava plants. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

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Figure 5
Leaf degreening (LD) in relation to application times and ethrel concentration during the vegetative development period (A and B) and preharvest period (C and D) of two culture cycles of cassava plants of the Caitité variety. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

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Table
1. Summary of variance analysis and coefficient of variation (CV) of fallen leaf number at 7 (LA7), 20 (LA20), and 70 days (LA70) after treatment, leaf degreening (LD), total leaf dry mass (LDM) and abscission speed index (ASI) for the Caitité variety cassava at different times of application (T) and ethrel concentrations (C).

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Figure 1 Precipitation (mm), atmospheric relative humidity (%), and maximum and minimum monthly average temperatures (°C) of the periods January2013 - July 2014 (A) and January2014 - July2015 (B).

Figure 2 Number of fallen leaves in the soil at 7 (LA7) and 70 days (LA70), and total leaf dry mass (LDM) according to application dates (A, C, and D) and ethrel concentrations (B, E, and F) in two culture cycles of Caitité variety cassava plants. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant difference by regression variance analysis at p ≤ 0.01% and p≤ 0.05, respectively.

Figure 3 Abscission speed index at 70 days (ASI70) and at 20 days (AVI20) after ethrel spraying relative to application time (A and C) and ethrel concentration (B and D) during the two cultivation cycles of cassava plants of the Caitité variety. For each ethrel concentration, means followed by the same letter do not differ from each other by the Tukey’s test (p ≤ 0,05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

Figure 4 Fallen leaf number at 7 (LA7) and 20 days after treatment (LA20), and total leaf dry mass 20 days after treatment in relation to the date of application and ethrel concentration (C. D and F) during the pre-harvesting period in two culture cycles of the Caitité variety cassava plants. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

Figure 5 Leaf degreening (LD) in relation to application times and ethrel concentration during the vegetative development period (A and B) and preharvest period (C and D) of two culture cycles of cassava plants of the Caitité variety. Means followed by the same letter do not differ from each other by the Tukey’s test(p≤ 0.05). **and*, significant by regression variance analysis at p ≤ 0.01% and p ≤ 0.05, respectively.

Table 1. Summary of variance analysis and coefficient of variation (CV) of fallen leaf number at 7 (LA7), 20 (LA20), and 70 days (LA70) after treatment, leaf degreening (LD), total leaf dry mass (LDM) and abscission speed index (ASI) for the Caitité variety cassava at different times of application (T) and ethrel concentrations (C).

Parameter	DF	Mean Square (x10³)
		Experiment 1					Experiment 2
		LA 7	LA20 70	LD	LDM	ASI	LA 7	LA 70	LD	LDM	ASI
T	2	679.7^**	587.2^**	2.8^**	524.5^**	247.9 ^**	301.7^**	59.1^**	17.4	223.1^**	32.7^**
C	4	246.5^**	56.0	1.5^**	8.5	46.9^**	214.9^**	45.1^**	202.3^*	52.5^**	11.2^**
T*C	8	22.0^*	11.7	0.2	11.4	8.6^**	46.6^**	8.8^**	20.2	6.6	4.0^**
Block	2	23.6	54.9	0.1	1.6	3.7	9.1	1.8	203.4^*	4.6	0.4
Residue	28	9.3	24.0	0.2	5.8	2.2	8.4	2.1	64.2	4.4	0.5
CV (%)		22.7	22.7	27.9	10.3	27.7	26.0	23.2	29.2	13.0	31.0

*Statistically significant at 5% probability, by F test.

A S I = \frac{\begin{matrix} N u m b e r o f f a l l e n l e a v e s \\ a t f i r s t d a y a f t e r t r e a t m e n t \end{matrix}}{D a y o f f i r s t c o u n t} + \frac{\begin{matrix} N u m b e r o f f a l l e n l e a v e s \\ a t d a y n a f t e r t r e a t m e n t \end{matrix}}{D a y o f f i n a l c o u n t (n)}

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Manihot leaf abscission induced by ethrel

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[1] *Author for correspondence. E-mail: lemoscarmem@yahoo.com.br