• Save
Grant Thorp
Upcoming SlideShare
Loading in...5
×

Like this? Share it with your network

Share
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
988
On Slideshare
987
From Embeds
1
Number of Embeds
1

Actions

Shares
Downloads
0
Comments
0
Likes
0

Embeds 1

http://www.slideshare.net 1

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. The New Zealand Institute for Plant & Food Research Limited Alternate bearing in ‘Hass’ avocado: possible role of carbohydrates and boron Grant Thorp, Helen Boldingh, Andrew Barnett and Peter Minchin Presentation to 4th Australian and New Zealand Avocado Growers Conference in Cairns, 23-24 July 2009
  • 2. Alternate bearing in ‘Hass’ avocado Does supply, transport and/or utilisation of carbohydrate and/or boron limit fruit set in avocado? The projects are examining: 1. seasonal availability of carbohydrate and boron in the tree 2. transport of carbohydrate and boron to the flower via the phloem and xylem 3. utilisation of carbohydrate and boron by the flower Related projects being reported at this conference include: • Avocado tree growth cycles – seasonal partitioning • Pollination – to confirm that pollen transfer was not limiting fruit set • Transpiration during avocado flowering – role of xylem transport The New Zealand Institute for Plant & Food Research Limited
  • 3. Project team Plant & Food Research Avocado Industry Council Grant Thorp Mt Albert Jonathan Dixon Peter Minchin Te Puke Henry Pak Sam Ong Eng Te Puke Toni Elmsley Andrew Barnett Te Puke Bart Hoftsee Mike Clearwater Te Puke Cindy Cotterel Bill Snelgar Te Puke Helen Boldingh Ruakura University of California Nick Gould Ruakura Dr Mary Lu Arpaia (avocado carbohydrates) Mark Goodwin Ruakura Dr Patrick Brown (boron transport) Lisa Evans Ruakura Jem Burden Mt Albert University of Malaga (Spain) Dr Inaki Hormaza (starch and fruit set) The New Zealand Institute for Plant & Food Research Limited
  • 4. Why are carbohydrates important? Carbohydrates are the major products of photosynthesis • Structural carbohydrates are found within cell walls and provide the structural support for plant growth • Non-structural carbohydrates provide the energy for plant growth Major “non-structural” carbohydrates in avocado are: • Starch (reserves) • Sucrose, glucose, fructose (6-carbon sugars) • D-mannoheptulose, perseitol (7-carbon sugars) The 7-carbon sugars appear to play an important role in overall tree physiology (Mary Lu Arpaia, University of California). Their availability and/or utilisation could be a limiting step in achieving successful fruit set The New Zealand Institute for Plant & Food Research Limited
  • 5. Boron transport in plants Boron is important for pollination and fruit set It is generally accepted that boron is not mobile within plants and that once boron accumulates in a plant tissue it can not be remobilised to other plant tissues However, in some plants (eg apple) boron is known to complex with sugar-alcohols, eg sorbitol, resulting in transport of a sorbitol-boron- sorbitol complex in the phloem from leaves to flowers (Patrick Brown, University of California) What about perseitol in avocado? It is a sugar alcohol. Does perseitol have a role in facilitating the transport of boron from leaves to flowers in avocado? The New Zealand Institute for Plant & Food Research Limited
  • 6. Alternate bearing in ‘Hass’ avocado: possible role of carbohydrates and boron Our hypothesis is that the seasonal accumulation and utilisation of 7- carbon sugars, in combination with a possible role in facilitating boron (B) transport, is a major regulatory process critical to achieving successful fruit set in avocado. Key experiments in Year 1: 1. Demonstrate that boron follows the same transport pathway as carbohydrates, from leaves to flowers 2. Compare carbohydrates and boron in ON and OFF cropping trees 3. Confirm that treatments which increase carbohydrate content of flowers also increase boron content, and thus increase fruit yields The New Zealand Institute for Plant & Food Research Limited
  • 7. Boron concentration in leaves If boron is transported in the xylem then it would accumulate in the old leaves as these leaves have transpired the most water. In avocado, boron concentration decreased with leaf age. This suggests that boron does not accumulate in the leaves but is being exported. 70 off year 60 on year Boron concentration (mg/kg) 50 40 30 20 10 0 very immature half-mature mature The New Zealand Institute for Plant & Food Research Limited
  • 8. Boron transport Boron isotope (B10) applied to leaves before flowering, then analysed at mid-bloom (24 October) in leaf and floral tissues. These studies confirmed the transport of boron from leaves to flowers (via the phloem) early 4 September 8 October late (50 days before mid-bloom) (16 days before mid-bloom) 4 4 off flowering 3 on flowering off flowering B10/B11 ratio 3 on flowering B10/B11 ratio 2 2 1 1 0 0 labelled flower leaf labelled peduncle flower new leaf leaf The New Zealand Institute for Plant & Food Research Limited
  • 9. Carbohydrates in ON and OFF flowering trees B starch sucrose glucose D A fructose C D-mannoheptulose perseitol E F (boron) ON bearing → OFF flowering OFF bearing → ON flowering The New Zealand Institute for Plant & Food Research Limited
  • 10. Avocado flower carbohydrates A v o c a d o flo w e r b u d c a rb o h y d ra te s o ff /o n y e a r ( C H O = m g /g m d w t) % dry D M % matter starch S ta r c h perseitol P e r s e ito l 30 16 40 14 25 12 30 20 10 15 8 20 6 10 4 10 5 2 0 0 0 ON flowering D-mannoheptulose M a n n o h e p tu lo s e glucose g lu c o s e fructose fr u c to s e 40 35 50 OFF flowering 30 30 40 25 20 30 20 15 20 10 10 10 5 0 0 0 sucrose total carbohydrates S u c ro s e T o ta l C H O 160 20 o n y e a r = o n flo w e r in g 140 15 120 100 10 80 60 5 40 20 0 0 The New Zealand Institute for Plant & Food Research Limited
  • 11. Avocado flower carbohydrates • Total carbohydrates are the same in flowers from ON and OFF bearing trees • Flowers on trees with a heavy crop load (few flowers) have low levels of starch • Flowers on trees with a low crop load (many flowers) have high levels of starch Agrees with work of Inaki Hormaza in Spain which indicates that flowers with high levels of starch are more likely to set fruit than flowers with low starch content The New Zealand Institute for Plant & Food Research Limited
  • 12. Can we increase the carbohydrate content of flowers? Branch girdling studies Thank you to Ron and Chris Bailey The New Zealand Institute for Plant & Food Research Limited
  • 13. Branch girdling study Paired branches (2-year-old growth units), one pair per tree Treatments applied to one branch from each pair in April 2008 Treatment Basal Diameter Length primary axis (n = 18 trees) (mm) (m) Girdle 60.0 2.4 No Girdle 62.1 2.4 Even mix of ON and OFF bearing trees (average 107 and 68 kg/tree) The New Zealand Institute for Plant & Food Research Limited
  • 14. Tissue sampling Sample F B Sample E Sample A D A Sample B C Sample C (wood) and D (bark) E F Black = 2005/06 branch Red = 2006/07 shoot and old leaves Blue = 2007/08 terminal shoot, fruit and new leaves Green = spring 2008 inflorescence The New Zealand Institute for Plant & Food Research Limited
  • 15. Leaves ON Bearing OFF Bearing Intact Girdled Intact Girdled Significance 1 Starch April (autumn) 16.4 18.2 17.5 11.5 NS October (mid-bloom) 7.5 17.4 8.8 31.1 (*) Perseitol April (autumn) 25.2 25.2 25.5 26.2 NS October (mid-bloom) 13.9 13.3 15.4 12.5 NS Boron April (autumn) 39.0 35.1 36.8 40.8 NS October (mid-bloom) 25.6 20.3 28.6 22.5 (*) Girdling treatments applied in April 2008 The New Zealand Institute for Plant & Food Research Limited
  • 16. Flowers ON Bearing OFF Bearing Intact Girdled Intact Girdled Significance 1 October 2008 (mid-bloom) Starch mg/g 22.4 22.7 20.5 18.8 NS Perseitol mg/g 17.9 17.1 19.0 18.3 NS Boron mg/kg 39.3 58.7 41.2 58.7 * Girdling treatments applied in April 2008 The New Zealand Institute for Plant & Food Research Limited
  • 17. Variable response to girdling 100 80 Boron (mg/kg) Boron (mg/kg)-log scale 60 40 Girdled OFF-G NotOFF-N girdled Girdled ON-G Not girdled ON-N OFF cropping Bearing-Girdling ON cropping The New Zealand Institute for Plant & Food Research Limited
  • 18. Summary and questions • As expected, girdling maintained high levels of starch in leaves on girdled branches, especially in OFF cropping trees • Boron was exported from leaves during April to October, with increased export from leaves on girdled branches – why? • Neither girdling nor crop load affected the starch and perseitol content of flowers, but girdling did increase the boron content of flowers on both ON and OFF cropping trees – why? • Not all branches responded to girdling – why? • Variable response to girdling suggests opportunities to improve the efficiency of this technique and thus improve its usefulness to growers wanting to achieve more consistent yields The New Zealand Institute for Plant & Food Research Limited
  • 19. The New Zealand Institute for Plant & Food Research Limited Thank you www.plantandfood.com grant.thorp@plantandfood.co.nz