Root growth and carbohydrate partitioning in cotton subjected to shading in the initial phase

Echer, Fábio Rafael; Zanfolin, Priscila Roberta Leme; Moreira, Ana Carolina Monico; Santos, Ana Cláudia Pacheco; Gorni, Pedro Henrique

doi:10.1590/0103-8478cr20180749

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CROP PRODUCTION • Cienc. Rural 49 (1) • 2019 • https://doi.org/10.1590/0103-8478cr20180749 copy

Root growth and carbohydrate partitioning in cotton subjected to shading in the initial phase

Crescimento radicular e partição de carboidratos em algodoeiro submetido ao sombreamento na fase inicial

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

Cotton cultivation in Brazil tends to occur mostly in the rainy season, and at the time of developing the crop there are often prolonged periods of low solar radiation. The objective of this work was to evaluate the root development of cotton cultivars subjected to shading in the initial phase. The experiment was carried out in a greenhouse, using rhizotrons. The experimental design was a 2x2 factorial in randomized blocks with five replications. The treatments were composed of cotton cultivars TMG 1WS (early) and TMG 8WS (late) and luminosity conditions: non-shaded and shaded (50% reduction of luminosity). There were no interactions between the factors “shading” and “cultivars” for any parameter evaluated. Shading reduced total and lateral root growth from the 21 days after emergence (DAE) and the main root at 24DAE. Shading caused reductions in length (60%), surface (65%), mean diameter (15%), root volume (69%), root dry matter mass (83%) and shoot (64%), as well as decreasing the content (36%) and the accumulation of carbohydrates in the shoot (73%). Shading at early cotton development reduces the shoot carbohydrates production, affecting dry matter accumulation and root growth, and this response is independent of the cultivar.

Key words:
root length; dry weight; radiation

Universidade Federal de Santa Maria Universidade Federal de Santa Maria, Centro de Ciências Rurais , 97105-900 Santa Maria RS Brazil , Tel.: +55 55 3220-8698 , Fax: +55 55 3220-8695 - Santa Maria - RS - Brazil
E-mail: cienciarural@mail.ufsm.br

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[1] E-mail: fabioecher@unoeste.br. ^*Corresponding author

	Tap root length	Lateral root length	Total root length	Plant height
Cultivar (C)	0.22	0.90	0.59	0.38
Shading (S)	0.01	0.000	0.000	0.11
DAE (D)	0.000	0.000	0.000	0.000
C x S	0,49	0.13	0.31	0.30
C x D	0.62	0.64	0.56	0.91
S x D	0.001	0.005	0.006	0.45
C x S x D	0.23	0.33	0.29	0.96
CV%	28.98	25.99	21.82	15.81

Shading	Root/Shoot ratio	L	S	AD	LV	RV
		m	cm^-²	mm	km m^-³	cm^-³

Shaded	0.050	18.1 b	288b	0.49 b	60.3 b	0.36 b
Non-shaded	0.081	45.6 a	811a	0.58 a	152.2 a	1.17 a
----------------------------------------------------------------------------Cultivar (C) ----------------------------------------------------------------------------
Late	0.069	33.5	578	0.536	111.7	0.804
Early	0.062	30.2	520	0.547	100.8	0.734
F Shade	5.045^ns	15.10^*	20.237 ^*	10.52 ^*	15.102 ^*	22.14 ^*
F Cultivar	0.17^ns	0.13^ns	0.132 ^ns	0.224 ^ns	0.132 ^ns	0.085 ^ns
F SxC	0.13^ns	0.06^ns	0.005 ^ns	1.703 ^ns	0.007 ^ns	0.011 ^ns
CV(%)	30.52	36.18	32.14	13.59	35.88	38.29

Shading (S)	--------------------------------------------------L per diameter class (mm)---------------------------------------
	0-0.5	0.5-2.0	2.0-5.0	5.0-10.0
	----------------------------------------------------------m---------------------------------------------------------
Shaded	13.5 b	4.1 b	0.38 b	0.009 b
Non-shaded	32.1 a	12.4 a	0.86 a	0.238 a
Cultivar (C)
Late	23.5	9.13	0.69	0.09
Early	22.1	7.41	0.55	0.15
F Shading	10.87^*	26.2^*	8.709^*	16.0^*
F Cultivar	0.05^ns	0.52^ns	0.63^ns	1.27^ns
F SxC	0.008^ns	0.008^ns	0.43^ns	0.46^ns
CV(%)	21.66	27.45	55.65	31.65

Shading (S)	------------Dry weight-----------		-------Carbohydrate content------		-------Carbohydrate accumulation------
	Root	Shoot	Root	Shoot	Root	Shoot
	------------g plant^-1---------------		-------------mg g^-1 DW------------		-----------------mg plant^-1-----------------
Shaded	0.04 b	1.01 b	6.47	29.64 b	0.33 b	33.81 b
Non-shaded	0.24 a	2.81 a	5.05	46.51 a	1.51 a	128.32 a
Cultivar (C)
Late	0.14	1.75	5.47	38.04	0.83	75.26
Early	0.15	2.08	6.04	38.11	1.00	86.88
F (Shading)	16.625^**	51.13^*	1.853^ns	24.81^**	31.36^**	74.56^**
F (Cultivar)	0.008^ns	1.290^ns	0.297^ns	0.000^ns	0.625^ns	1.11^ns
F (SxC)	0.054^ns	0.000^ns	0.004^ns	0.000^ns	0.734^ns	0.23^ns
CV(%)	25.50	30.20	40.30	19.90	29.80	30.19