Plant analyses: comparison of systems

4.2 Ebb-and-flow technique

4.4.2 Plant analyses: comparison of systems

A plant analysis was conducted on plants in each of the systems and the results compared. The only difference between these treatments was the hydroponic system itself, the same three clones were used and the same nutrient solution was used with identical pH and EC. For comparisons among systems, the plant nutrient content of the mother materialwas averaged over the eightsubstrates for theNFT at harvest 3.

For all macroelements, the clone and the clone by system interaction was not significant. System type was significant for all macroelements except K levels (Table 26). For all themacroelements, a pattern wasevidentfor all clones within eachelement (Figure 35). Plants inthe aeroponic system had the highestN and P levels (Figure 35).

PlantK levels were highest, although not significantly, in plants grown in the ebb-and- flow system while Ca and Mg concentrations were the highest in plants grown in the NFT system (Figure 35). For N, K and Mg concentrations, there were no significant differences betweenclones inthe aeroponicsystem (Figure 35).

For clone GN107, thePconcentrationof plants in thethreesystems were notsignificant (Figure 35). For clone NHOO and GN 156, the P concentration from the plants in the aeroponics system was significantly higher than those in theothertwo systems (Figure 35).

Plantsin the NFTsystem hadsignificantlyhigher Caconcentrations compared to plants grown in the other two systems (Figure 35). Clones GN107 and GN156 had a significantlyhigherconcentrationthan clone NHOOintheNFTsystem(Figure 35).

With regardto themicroelements, clone type and the interaction(clone by system) had a significant effect on Cu, Mn and B concentrations. The system type had a significant effectonallmicroelements(Table 26).

Plant Fe was highest inplants in the aeroponics system except for clone GNI07 where motherplantsinthe NFT werehigheralthoughnot significantly(Figure 36).Thelowest Fe levels were found (in all clones)in the ebb-and-flow system. For clones GN 107and

118

NHOO, plants in the NFT system showed significantly higher levels of Fe compared to plantsin the ebb-and-flow system.

4 0.6

Nitrogen Phosphorus

d

a ~0.5

~ ~

3 <:

<: g ^0.4

gs _~~

C ₂ 0.3 _ab

Q) (J

(J <:

1

<: 0

0 (J 0.2

(J C

CIII 1 ^III

a:: 0.1

a::

0

GN107 GN156 NHOO

GN107 GN156 NHOO

2.5

a

>R 2 ^~0.8

~ <:

<: ⁰

0 ~ ^0.6

~ ^1.5 C

C fl

fl 5 0.4

<:₀ 1 ^(J

(J c

C ^III

III a:: 0.2

a:: 0.5

0

NHOO GN107 GN156 NHOO

GN107 GN156

0.4

~~0.3

<:

s

~ • Aeroponics

~ ^0.2 oEbb-and-flow

<: . NFT

8

~ ^0.1 a::

0

GN107 GN156 NHOO

Figure 35: Concentration of macroelements (%) in three clones (GNI07, GN156 and NHOO) maintained in three hydroponic systems (NFT, ebb-and-flow, aeroponics)(p < 0.05)

For plant Cu, there wasnoparticularsystem that produced the highestconcentrations in all clones (Figure36). ForclonesGN107 and NHOO, plantsin the aeroponicsystem had the highest Cu concentration followed by those in the NFT and ebb-and-flow systems, respectively (Figure 36). For clone GN156, plants in the ebb-and-flow system had the highest Cu concentration followed by plants in the aeroponics and NFT systems, respectively (Figure 36). Only in the NFT system were concentrations similar among the clones (Figure 36). For plants in the aeroponics system, clone GNI07 had a

significantlyhigherCu concentratio n than clone GN156, whichwas slightly higher than NHOO, although notsignificantly(Figure 36).For the plants in the ebb-and-flow system, clone GN 156 had the highest Cu concentration with clones GNl07 and NHOO being significantlylower (Figure 36).

For all clonesgrown in the aeroponicsystem Zn concentrationwere highest (Figure36).

The mother plants in the NFT system gave the next highest conce ntrations,which were significantly higher than those inthe ebb-and-flow system.

For Mn concentrations, NFT plants had significantly higher result than the other two systems followed byplantskept in the aeroponics,which were significantly higher than those in theebb-and-flowsystem(Figure 36).

Boron concentrations also had a trend across the different systems with plants in NFT giving significantly higher values across all clones (Figure 36). For GN107 mother plants, the other two systems are not significantly different but for GN156 and NHOO mother plants,aeroponicswas significantlyhigherthan the ebb-and-flow results.

One could see there was a distinct pattern for all three clones with regards to the response to nutrients delivered via each system except for Cu concentration. This indicated that not only was the method of delivering the nutrient solution different for each system but the availability of the individual nutrients was affected bythisand the presence or absence ofsubstrates may have also influen ced the nutrients' availability.

As mentioned earlier, oxygen levels in the nutrient solution were notmeasured but this would have influenced the nutrient availability and the forms in which nutrients are takenup.Plants withinthedifferent systems produced differentroot systems (Figure 37, 38 & 39)and this mayhaveinfluenced the availability of the nutrients.

In the aeroponic s system, the root growth was rapid (Figure 37) with many white roots which are actively growing and taking up nutrients. The plants in the ebb-and-flow system produced a mass of roots (Figure 38). Many were white and therefore actively growing. The plants in theNFT system produced a mass of roots (Figure 39) although not as many werewhiteas in the other two systems.

120

• Aeroponics

o

Ebb-and-flow

. NFT

20 Copper

...

~ f cil15

.s

c .Q

~ ¹⁰

"E

s

_c

00

Ctil

0::

GN107 GN156 NHOO

400 ...

c"

.x:

cil300

.s

c .Q

~ ²⁰⁰ C

s

_c

8100 C 0::til

0

GN107 GN156 NHOO

;:- 100 Iron

c

c"

...,

0> 80

.s

c

.Q 60

~"E

2l_c 40

00

Ctil

a::

GN107 GN156 NHOO

140

6,120

~

r

¹⁰⁰

gc ⁸⁰

"El!! 60

2l_c

00

"E

til

0::

GN107 GN156 NHOO

50

~ Boron

~⁴⁰ d

.s

Cl

530

""~

~ ²⁰

c8

"E 10

a::til

0

GN107 GN156 NHOO

Figure 36: Concentration of microelements (mg.kg") in three clones (GNI07, GN156 and NHOO) maintained in three hydroponic systems (NFT, ebb-and-flow, aeroponics) (p <0.05)

Clone x system interaction System

Table 26: Summary of analyses ofva r iance for plant analyses measurements when comparing the three hydroponic systems

Clone

N(%) P= 0.780 p=0.023

P P= 0.975 p<0.001

K P= 0.924 p=0.464

Ca p = 0.333

P

<0.00 1

Mg

P

=0.990 p=0.014

Fe (mg.kg-I) p=0.21O p=0.001

Cu

P

<0.001

P

<0.001

Zn p=0.187 P<0.001

Mn p<0.001

P

<0.001

B P<0.00 1 p<0.001

p=0.937 p=0.591 p= 0.999 p=0.903 p=0.998 p=0.178 p<0.001 p =0.959 p<0.00 1

p

<0.001

"

Figure 37: Root growth of mother plants in the aeroponics table at different stages (Five days, two weeks and approximately six months - end of trial)

From theseand previous results,it appearedthat Ca concentration playeda critical role in the rooting process. It has already been established (Figure 34) that plants from the hedges in the NFT system hadthebest rooting results. From data in Figure 35, itwould appear that these plants required a minimum Ca concentration of 0.7 %. Higashiet al., (2000a) recommended a Ca range of 0.5 - 0.7 %; Carlson et al., (2003) recommended 0.26 - 1.49 % Ca and from Section 4.1.2 it would appear that for ON hybrids a higher level of Cawas required for optimal rooting.

122

Figure38:Root growth from motherplantsestabli shed in the ebb-and-flow table

Figure39:Root growth from mother plants established in the NFT table in gravel, NFT,perlite and sandsubstrates

If Zn, Mn and B were all as important as was previously discussed, then these results and the critical ranges determined by Higashi et al. (2000a) concurred. Higashi et al.

(2000a) reported that the best ranges for the production of micro-cuttings was 30 - 60 mg.kg" Zn,250 -500mg.kg" Mn and 35 - 70 mg.kg" B.In Figure 35,theplants grown in the aeroponics system showedthehighestaccumulation ofZn but this was abovethe Higashietal. (2000a)recommended limit. The plantsgrown in theNFTsystem all had a Zn leveljust below 60 mg.kg' which was within the Highashi et al. (2000a) range.

From Figure 36, the plants grown in the NFT system both have levels of Mn and B, respectively,which fall into Higashi et al. (2000a) suggested rangewhereas none of the otherplants in theother two systemsdo.

The NFT systemresulted in the highestrootingpercentages overalland fromtheseplant analyses it wouldappear that the concentrations ofCa, Zn,Mn and B were critical.

4.5 Correlation between rootingand concentratio ns of plant elements

In an effort to verify the findings further in the previous section a series of correlation graphswere produced (Figures 40 & 41).These graphscomparedrooting data with the concentration of essential elements within the plants. A statistical correlation was not performed as therewasinsufficient data.

For all three clonesrooting decreases as N and Kconcentrations in the plantsincreased (Figure 40). Plant P, Mg and Na concentrations appeared to be fairly constant and therefore didnot seemto play any significant roleintherooting process.

Of all the macroelementsonlyCa concentrationchanged significantlybetweenplants in systems. In the separate graphs, one can see that as Ca concentration decreased so too did the rooting, in keeping with the suggestion that Ca plays a role inrooting.Rooting wasreduced atplant Ca concentrationsbelow0.7 %.

The relationship between rooting and plant micronutrient concentrations are shown in Figure 41. There was considerable variation in micronutrient content in plants from differentsystem s.

Iron concentrations didnot appearto haveany effectonrootingperformance.If Cuand Zn concentrations were either too high or too low the rooting performance decreased. The critical range for Cu was:9- 11 mg.kg" and forZn: 50- 80 mg.kg". For Mnand B concentrations, as the concentration decreased so too did the rooting. The critical minimum' s for Mn were: 250 mg.kg" and B: 35 mg.kg".

124

10

70 ~---,

3.2

'.

1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

Concentrationwithin plant(%) 10

Phosphorus

60

*

-;50

'"

"40

I1l_~

~30

'"

c:

'i5 20

fi.

Nitroge n

60

oL---~

0.230 0.255 0.28 0.305 0.33 0.355 0.38 0.405 0.43 Concentrationwithinplant(%)

~~50

'"

"

I1l_~

40

~30

'"^c:

'i5o 20 0::

70 ,- - - - - - - - - - - - - - - - - - - , 70,- - - - - - - - - - - - - - - - - - - - -

oL-- - - -- - - ----'

0.44 0.49 0.54 0.59 0.64 0.69 0.74 0.79 0.84 0.89 0.94 Concentration withinplant(%)

60

"#-;50

'"^I1l

"

_~

40

~30

'"

c:

'i5 20 0::o

10

Potassium

1.25 1.35 1.45 1.55 1.65 1.75 1.85 1.95 2.05 Concentrationwithin plant(%)

60

*

-; 50 1'Jco C:4O

~~30 coe

'i5o 20 0::

10 Calcium

70 , -- - - -- - - -- - - - - - - - -- - - , 70,- - - - - - - -- - - - - - - - - - - - - -,

0L..-- - - - - - - - _

0.120 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 Concentration wrthin plant(%)

- - NHOO ..•..GN156 ~GN107 60

~ ' ;50

'"

"

I1l_~

40

~30

'"

'i5c: 20 0::o

10

0.21 0.24 0.27 0.30 0.33

Concentration withinplant(%)

!---'-'- '-'-' -

0.36

60

*

i ..

^SO

"

_~

40

~30

0>

sc:o 20 a::

10 Sodium

Figure 40:Correlation of rooting and macroelements for cold-tolerant Eucalyptus hybrids

From these and previous results, it would appear that Ca, Cu, Zn , Mn and B concentr ation s may play a role in the rooting process and that for ON hybrids, these critica lvaluesor ranges were slightlydifferent tootherEucalyptus hybrids (Table27).

14 13

- .

,

Copper

8 9 10 11 12

Concentration withinplant(mg.kg-1)

70 70

Iron

60 t-.

_ . -

60

ij , .-,- _i1

;"50 ;"50

0>

C> s

'"

<:40 " 40

~ ~

~30 ~³⁰

C> 0>

"

" ^'520

'520 0

0 a:

a:

10 10

0 0

70 75 80 85 90 95 100 105 110 115 120 125 130 135 6.0 7 Concentrationwithinplant(mg.kg- l)

70 70

60 Zinc ⁶⁰

;i ij

;"50 ;"50

C> C>

'"

'" 53 ⁴⁰

~ 40

e e

~30 ~30

C> C>

" ^, "

'5 20

, '520

0 0

a: a:

10 10

Figure 41: Correlation of rooting and microelements for cold-tolerant Eucalyptus hybrids

Table 27: Critical concentrations of Ca, Cu, Zn, Mn and B for optimal rooting of cold tolerantEucalyptus grandisxE.nitenshybrids

Element Higashiet ai., Carlsonet al.,

(2000a) (2003)

Ca% 5- 7 0.26 - 1.49

Results from the trials evaluated ¹⁰ thischapter

0.7minimum

B mg.kg-^t

250 minimum 35 minimum 9- 11 50- 80 37- 70

250- 500 30- 60 8- 15 Mn mg.kg-^I

Cu mg.kg-^l Zn mg.kg-^I

126

Chapter 5