W. Roland Leatherwood1

Neil S. Mattson1

Possible Roles of Silicon and Regulated Deficit Irrigation on Poinsettia Plant Quality and Postharvest Performance

1Department of Horticulture, Cornell University

Silicon Background• Abiotic stress

– Improved adventitious rooting (Moon 2008, Gillman 2000), Decreased leaf abscission (Gillman 2000)

– Heat stress (Agarie 2008)– Drought Stress (Gao 2004, Agarie 2008)

• Horticultural characteristics– Flower diameter, stem caliper (Kamenidou 2008,

2005), branching (Moon 2008)• Little on Si & Greenhouse Crops

– Industry acceptance of Si as supplemental nutrient is uneven

Methods

• Plant material– ‘Prestige Red’ and ‘Peterstar Red’ Poinsettia

rooted cuttings– 6” Pots, commercial media.– Nutrition

• N 200 mg·L-1 (21-5-20) • Mg 30 mg·L-1 (MgSO4 · 7H20)• S 32 mg·L-1 (MgSO4 · 7H20)• Mo 0.1 mg·L-1 (Na2Mo4 · 2H2O)

Methods• Treatment design

– CRD, 15 replicates– Two way factorial of deficit irrigation and silicon

supplementation• 100, 80 and 60% RDI• Si 0 and 56 mg·L-1 (KSiO3) (2 mM)

– Statistical analysis• SAS V9.1 Tukey’s HSD with an α=0.05

– Irrigation water (RO) Si was ND and substrate Si concentration was 2.0 mg·L-1

Hei

ght (

cm)

2017 24 31 38 45 52 59 66 73

Days After Pinch

21

22

23

24

25

26

27

28

29

30

31

32

33

79

S- 100%S- 80%S- 60%S+ 100%S+ 80%S+ 60%

Peterstar

Cultivar Treatment Height (cm)

Peterstar Si- 100% 31.0 A Si+ 100% 30.0 AB Si+ 80% 29.7 BC Si+ 60% 29.6 BC

Si- 80% 28.8 BC Si- 60% 28.5 C

Significance *n=15, NS = not significant, * = 0.05, ** = 0.01.

PeterstarA

rea

(cm

2 )

0

500

1000

1500

2000

2500

3000

Leaf Bract Transition

Tissue Type

S+ 100%S- 100%S+ 80%S- 80%S+ 60%S- 60%

Are

a (c

m2 )

0

500

1000

1500

2000

2500

3000

Leaf Bract Transition

Tissue Type

S+ 100%S- 100%S+ 80%S- 80%S+ 60%S- 60%

Prestige

Disease

Disease

Treatment Total Plants Effected

Peterstar1 Prestige2

Si+ 100% 0 0Si+ 80% 0 0Si+ 60% 0 0Si- 100% 1 1Si- 80% 1 1Si- 60% 0 1

Significance1 χ2 (2, n=15)=?, p=?2 χ2 (2, n=15)=?, p=?

Strength

Photo B. Whipker

Strength

Cultivar Treatment Number of Plants with

Breaks

Average Break Height (cm)

Prestige Si+ 100% 0 50Si- 100% 2* 40*Si+ 80% 1 40Si- 80% 1 50Si+ 60% 1 40Si- 60% 0 50

χ2 (2, n=5)=3.95, p<0.0382

Findings

• Si interacts with plant water status giving differential results– No or moderate water stress, Si decreased

height and bract area– Severe water stress, Si increased height and

bract area• Si improves lateral branch strength and

may reduce Pythium occurrence.

Postharvest

Materials & Methods

• Plants were thoroughly watered• Moved to postharvest December 1st • Leaf angle measured 12/1 and periodically

thereafter terminating December 17th • Measured uppermost fully expanded free

hanging green leaves (3x)• 12 Hour day, florescent lighting, 21° C

Postharvest Wilt

Postharvest Wilt17 Days Postharvest

Cultivar Treatment Leaf Angle(°)

Peterstar Si- 100% 42.1 A Si- 60% 34.0 AB Si- 80% 28.4 B Si+ 100% 25.5 B Si+ 60% 21.8 B Si+ 80% 21.0 B

Significance **n=10, NS = not significant, * = 0.05, ** = 0.01.

Postharvest Wilt

Bract Edge Burn

Bract Edge Burn

Treatment Total Lesions

Peterstar1 Prestige2

Si+ 100% 10 1 Si- 100% 21* 6* Si+ 80% 20 1 Si- 80% 22 1 Si+ 60% 12 0 Si- 60% 6* 2*

Significance1 χ2 (2, n=10)=5.49, p<0.02012 χ2 (2, n=10)=1.91, p<0.0835

Findings

• Si supplementation forestalls wilt and may improve recovery from water stress

• There may be interactions with RDI and Si• Si supplementation reduces BEB in well

watered plants and may increase it in water stressed plants

Acknowledgements

• Post/Schenkel Endowment• USDA Hatch Funds • Ecke Ranch• Rachel Brinkman