Plant densities and harvesting times on productive and physiological aspects of Stevia rebaudiana Bertoni grown in southern Brazil

GOMES, ERIK N.; MOTERLE, DIEGO; BIASI, LUIZ ANTONIO; KOEHLER, HENRIQUE S.; KANIS, LUIZ ALBERTO; DESCHAMPS, CÍCERO

doi:10.1590/0001-3765201820170510

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Agrarian Sciences • An. Acad. Bras. Ciênc. 90 (4) • Oct-Dec 2018 • https://doi.org/10.1590/0001-3765201820170510 copy

Plant densities and harvesting times on productive and physiological aspects of Stevia rebaudiana Bertoni grown in southern Brazil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Stevia (stevia rebaudiana Bertoni) is a species characterized by producing non-caloric substances with high sweetening potential. Among these substances, rebaudioside A and stevioside are produced in greater quantity. Plant density and harvesting time are factors that affects biomass and sweetening compounds yield in this species. The objective of this research was to evaluate the effect of plant densities and harvesting times on the productive and physiological characteristics of stevia in southern Brazil. The experimental design was in randomized blocks, in a split-plot scheme, with 9 treatments comparing the effect of three planting densities (166 667, 83 333 and 33 333 plants ha^-1) in the plots and three harvesting periods (before, in the beginning and in full flowering) in the subplots. Harvesting at the beginning of flowering promoted higher dry leaf biomass yield and, when associated with the lowest planting density, promoted higher levels of rebaudioside A and stevioside. The lowest planting density resulted in greater leaves biomass accumulation, whereas the highest density promoted higher yields per area. Interaction between density of 166 667 plants ha^-1 and the harvest at the onset of flowering promoted higher yields of rebaudioside A (43.22 kg ha^-1) as well as higher rebaudioside A/stevioside ratio (0.60).

Key words
diterpene glycosides; natural sweetener; rebaudioside A; stevioside

Variables	Month/year

	NOV/2015	DEC/2015	JAN/2016	FEB/2016
Precipitation (mm)¹	112.70	200.40	164.20	289.30
Relative humidity (%)¹	90.98	88.57	86.35	89.46
Average Maximum Temperatures (ºC)¹	24.47	26.46	26.06	27.78
Average Minimum Temperatures (ºC)¹	15.61	17.48	16.67	18.16
Average temperature (°C)¹	18.81	20.91	20.42	21.55
Global radiation (kJ m^-2)²	1007.18	1164.10	1386.56	1179.82
Day length (h)³	13.3	13.6	13.4	12.9

Granulometry
Clay		Silt				Total Sand				Thick Sand			Fine Sand
---------------------------------- g kg^-1 -----------------------------------
513		175				313				141			172
Chemical Characteristics
pH			Al⁺³	H⁺+Al⁺³	Ca⁺²		Mg⁺²	K⁺	SB		T	P		C	V
CaCl₂	SMP		----------------------- cmol_c dm^-3 ------------------------									mg dm^-3		g dm^-3	%
6.0	6.3		0.0	4.00	6.50		2.90	0.65	10.05		14.05	46.20		28.9	72

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[1] Correspondence to: Erik Nunes Gomes E-mail: e93gomes@gmail.com

Planting densities	Variable	166 667 plants ha^-1	83 333 plants ha^-1	33 333 plants ha^-1	LSD
	Height (cm)	54.05^ns	57.97	55.79	7.43
	Number of branches	14.66^ns	18.77	18.28	6.46
	Leaf area index	1.45 a	1.05 b	0.59 c	0.39
	Specific leaf area (cm² g^-1)	24.75^ns	19.61	24.71	8.29
	Leaf mass ratio (g g^-1)	0.50^ns	0.51	0.55	0.04
	Leaf area ratio (cm² g^-1)	13.71^ns	11.18	14.54	4.54
Harvesting times	Variable	Before flowering	Onset of flowering	Full flowering
	Height (cm)	44.54 b	61.41 a	61.85 a	2.54
	Number of branches	9.74 b	20.96 a	21.05 a	2.60
	Leaf area index	0.62 b	1.32 a	1.15 a	0.36
	Specific leaf area (cm² g^-1)	14.63 b	28.61 a	25.82 a	10.02
	Leaf mass ratio (g g^-1)	0.56^ns	0.48	0.51	0.01
	Leaf area ratio (cm² g^-1)	8.33 b	16.40 a	14.70 a	5.76

Planting densities	Variable	166 667plants ha^-1	83 333plants ha^-1	33 333plants ha^-1	LSD
	Dry mass of leaves (g plant^-1)	6.32 b	10.65 ab	14.30 a	5.64
	Dry mass of aerial part (g plant^-1)	12.69 b	21.22 ab	26.31 a	10.82
	Leaves dry mass yield (kg ha^-1)	1053.67 a	887.40 ab	476.83 b	534.12
Harvesting times	Variable	Before flowering	Onset of flowering	Full flowering
	Dry mass of leaves (g plant^-1)	5.46 b	11.63 a	14.18 a	4.94
	Dry mass of aerial part (g plant^-1)	9.69 b	24.07 a	26.31 a	6.15
	Leaves dry mass yield (kg ha^-1)	433.40 b	943.82 a	1040.67 a	334.02

Harvesting time	Planting densities (plants ha^-1)
Harvesting time	166 667	83 333	33 333		Mean
Before flowering	1061.55 bA	870.80 bA		408.22 bA	780.19
Onset of flowering	1985.01 aA	2213.87 aA		984.24 abB	1737.63
Full flowering	2596.49 aA	1549.52 aB		1223.51 aB	1789.84
Mean	1881.01	1655.65		871.99
LSD for columns 665.63; LSD for rows 855.94. Significant interaction (P = 0.0193)

Planting densities	Variable	166 667plants ha^-1	83 333plants ha^-1	33 333plants ha^-1	LSD
	Chlorophyll a (mg/cm²)	0.065 b	0.080 a	0.078 a	0.007
	Chlorophyll b (mg/cm²)	0.035^ns	0.041	0.036	0.009
	Total Chlorophyll (mg/cm²)	0.100 b	0.121 a	0.115 a	0.014
	Proteins (mg/g)	49.03^ns	49.59	53.20	13.41
	Sugars (mg/g)	422.30^ns	382.47	467.62	105.37
Harvesting times	Variable	Before flowering	Onset of flowering	Full flowering
	Chlorophyll a (mg/cm²)	0.068^ns	0.074	0.081	0.017
	Chlorophyll b (mg/cm²)	0.036^ns	0.037	0.039	0.009
	Total Chlorophyll (mg/cm²)	0.105^ns	0.111	0.120	0.025
	Proteins (mg/g)	62.09 a	44.59 b	45.14 b	11.96
	Sugars (mg/g)	462.81 a	428.85 ab	369.72 b	76.31

Harvesting time	Plant densities (plants ha^-1)
	Stevioside content (mg g^-1)
	166 667	83 333	33 333		Mean
Before Flowering	71.02 aA	62.36 aA		67.81bA	67.06
Onset of Flowering	56.76 bB	48.52 bB		86.98 aA	64.08
Full Flowering	43.51 cA	46.29 bA		55.48 bA	48.42
Mean	57.09	52.39		70.09
LSD for columns 12.98; LSD for rows 13.44. Significant interaction (P=0.0004)
	Rebaudioside A content (mg g^-1)
Before Flowering	26.34 aA	24.82 aA		30.19 bA	27.11
Onset of Flowering	33.60 bB	22.56 bB		47.31 aA	34.48
Full Flowering	17.65 cA	20.99 bA		30.06 bA	22.90
Mean	25.86	22.80		35.86
LSD for columns 8.45; LSD for rows 9.08. Significant interaction (P=0.0037)
	Rebaudioside A/stevioside ratio
Before Flowering	0.37 bB	0.40 bAB		0.45 bA	0.40
Onset of Flowering	0.60 aA	0.47 aB		0.54 aA	0.53
Full Flowering	0.41 bB	0.45 abB		0.54 aA	0.46
Mean	0.46	0.43		0.51
LSD for columns 0.06; LSD for rows 0.07. Significant interaction (P= 0.0002)
	Stevioside yield (kg ha^-1)
Before Flowering	40.76	30.46		15.97	29.06 b
Onset of Flowering	73.21	51.94		39.65	54.94 a
Full Flowering	54.60	50.47		39.89	48.32 a
Mean	56.19 A	44.29 B		31.84 C
LSD for columns 9.42; LSD for rows 10.35. Non-significant interaction (P= 0.3713)
	Rebaudioside A yield (kg ha^-1)
Before Flowering	15.14 bA	11.91 bA		7.05 bA	11.36
Onset of Flowering	43.22 aA	24.20 aB		21.35 aB	29.59
Full Flowering	22.68 bA	23.70 aA		21.68 aA	22.69
Mean	27.02	19.93		16.69
LSD for columns 9.14; LSD for rows 8.97. Significant interaction (P= 0.0033)