EFFECTS OF CROP LOAD ON VEGETATIVE GROWTH OF CITRUS

Transcription

1 EFFECTS OF CROP LOAD ON VEGETATIVE GROWTH OF CITRUS HOS 6545 ADVANCED CITRICULTURE I Regulation of Vegetative Growth L. GENE ALBRIGO

2 Smith, P.F Collapse of Murcott tangerine trees. J. Amer. Soc. Hort. Sci. 101: Murcott trees set heavy crops and tend to alternate bear Trees can decline or collapse with heavy crop Decline was attributed to deficiency (high crop use) of N and K PURPOSE: Determine role of N and K and other factors on tree collapse

3 MATERIALS AND METHODS N and K fertilization studies developed Measurements broadened to include starch trends and feeder root density Crop thinning instituted to evaluate crop impact on starch reserves

4 Relation of N and K fertilization to collapse of Murcott trees

5 Starch levels in different plant parts of Murcott trees with and without crop compared to Valencia, a mild alternate bearing cultivar. No fruit (empty) Murcott trees are broken lines with open circles.

6 Effect of crop load on feeder root density for Murcott trees.

7 Effect of fruit thinning at May-June drop on tree collapse.

8 RESULTS Collapse related more to starch levels than to leaf N and K Feeder root density diminished by crop load

9 DISCUSSION AND CONCLUSIONS Similar result to Wilking mandarin except trees of latter not reported to collapse, just become completely non-flowering. Difference of warm climate? Or cultivar and fruit requirement for carbohydrates and nutrients Industry feeds Murcott at higher N and K rates.

10 Summary and Conclusions Fruit greatly changed distribution of dry matter development. Would have been more informative if total shoots, length and # buds were reported Fruit did not greatly reduce leaf nutrient levels Main effect on carbohydrates and not nutrition K levels should have been measured since K amount in fruit largest

11 Goldschmidt, E.E. and A. Golomb The carbohydrate balance of alternate-bearing citrus trees and the significance of reserves for flowering and fruiting. J. Amer. Soc. Hort. Sci. 107: After structural use of photosynthate, soluble carbohydrates make up a pool that may be distributed among sinks and redistributed Alternate bearing trees (On and Off) are a good comparison to understand this distribution PURPOSE: Determine the balance of carbohydrates in plant parts of Wilking mandarin trees to see how crop load alters distribution and perhaps accounts for alternate bearing

12 MATERIALS AND METHODS Two 15 year old Wilking mandarin trees selected, one in its On-year and one in its OFF-year. On-tree thinned and provided extra K nutrition Trees dissected into 11 parts, estimated about 75 % root recovery Oven dried samples prepared and run for starch and soluble sugars

13 Distribution of starch and soluble sugars in On and Off trees

14 Total dry matter, starch and soluble sugars of organs in Off and On trees Total dry matter nearly equal, but distribution different. Starch and soluble sugars much larger pools in Off tree. Surprising reduction in major root dry matter (root loss?)

15 Leaf starch, buds per shoot and bud break types in following Spring for On, Off and On-year trees with fruit removed by mid-summer. Off and On-defruited tree had more buds/shoot (? Which shoots) and less return vegetative buds.

16 Results Fruit greatly reduced the amount of dry weight in leaves, stems and roots. On fruit biggest affect. Fruit did not reduce leaf N or P very much

17 RESULTS Fruit load clearly deprived rest of tree of carbohydrate reserves. Roots a major loser in all size roots. Impact on next year s growth and therefore buds for following crop.

18 DISCUSSION AND CONCLUSIONS Small sample size, but difficult samples to work with. Clear indication of suppressed canopy growth with heavy crop and its impact on next year s crop potential.

19 Lenz, F.. Relationships between the vegetative and reproductive growth of Washington navel orange cuttings (Citrus sinensis L. Osbeck). Issue of crop load on vegetative growth and subsequent reproduction not completely understood Small plant units could furnish good experimental system PURPOSE: Determine effect of yield, defoliation and defruiting on citrus tree growth

20 MATERIALS AND METHODS Cuttings from a mature Washington navel tree rooted and developed in greenhouse Plants in pots selected with 0, 1, 2 or 3 fruit. Various measurements over time made to plants as per results.

21 Relative tree size of potted trees with 0, 1, 2 or 3 fruit

22 P l a n t s i z e Growth and weight of plant parts with V (0), I (1), II (2) or III (3) fruit

23 RESULTS Fruit reduced plant size, but increased total weight Leaves, stems and roots reduced by fruit

24 DISCUSSION AND CONCLUSIONS One of earliest studies showing reduced growth of vegetative parts when crop present. All parts reduced Clearly balance of crop and vegetative growth needed Renewal of vegetative growth is first step to sustained productivity of mature trees

25 Lenz, F. and P.R. Cary Relationships between the vegetative and reproductive growth of Washington Navel orange as affected by nutrition. Proc. Ist Internl. Citrus Symp. 1968, 3: Alternate bearing results from the current crop load suppressing flowering and set of the next crop. Measurement of reproductive versus vegetative response is difficult on mature trees. This study on small trees, nutritional levels and fruit numbers were regulated to determine vegetative and fruit growth

26 Materials and Methods 4 fruit #/plant and 4 nutritional levels times 8 replications Fruit numbers adjusted at flowering and early set (0 to 3 fruit per plant Nutritional levels of 0, 2, 4 or 8 kg NH 4 SO 4 /tree/year Dry matter of plant parts measured

27 Different inflorescence types Vegetative only not shown

28 Nutrient levels by nutritional treatment level N, S, P (no M&M info except table)

29 Dry weight of plant parts Shown by nutrition and fruit number

30 Mean leaf levels of N and P by treatment and fruit number per plant

31 Sanz, A., C. Martinez Cortina and J.L. Guardiolla The effect of the fruit and exogenous hormones on leaf expansion and composition of citrus. J. Expt. Bot. 38: Inter-relation exists between reproductive and vegetative growth Reproductive growth depends on vegetative In perennial crop, the reverse can occur also Details of inter-relationship needed attention PURPOSE: Determine how early flower & fruit growth affect leaf development. See if invertase activity mediates the effect.

32 MATERIALS AND METHODS Tests on 16 year old Washington navel trees 24 days before full bloom (5 April), flower removed from single flower inflorescences or left undisturbed Some received IAA, GA or Kn Leaves sampled on 22 April, 6 and 21 May 50% flowers open, post bloom and after full leaf size Leaf size, carbohydrates and enzymes determined

33 Dry matter accumulation by two dates, 17 and 37 days after deflowering, of whole inflorescence with flowers (date 1) or fruitlets (date 2) Dry matter (mg/sprout) Date of growth regulator applications not given

34 Leaf dry weight and mineral content in vegetative sprouts and intact or deflorate inflorescences.

35 Effect of inflorescence flower on leaf area development, total and relative growth rate for vegetative shoots (triangles) and shoots with one flower or one fruitlet (circles) LA Note leaf expansion nearly finished by bloom RGR Days after full bloom

36 Starch and soluble sugar contents in leaves on 21 May (full leaf expansion) Vegetative and inflorescence shoots not different by this time

37 RESULTS Flowering shoots had smaller leaves with less dry matter Mineral nutrition was also lower These same effects occurred even when the flower was removed before bloom

38 DISCUSSION AND CONCLUSIONS No information on GR application date Authors interpret the differences to sink strength perhaps from GA content since GA stimulated leaf growth in deflorate shoots but vegetative shoots grew better Influence of flower development prior to visible expansion may be more important than expected. Also sets # leaves & maybe leaf size Need measurements of dry weight or leaf size at earlier expansion stage

39 Garcia-Luis, A., M. Kanduser, and J.L. Guardiola The influence of fruiting on the bud sprouting and flower induction responses to chilling in Citrus. J. Hort. Sci. 70: Data on possible fruit and temperature interaction not well studied Fruiting and non-fruiting trees compared in field and also potted trees temperature treated in a growth chamber

40 Materials and Methods Owari satsuma trees in field and growth chambers Field trees normal or crop removed Chamber trees normal or de-fruited and then subjected to 26/20 or 26/13 or 15/10 D/N temps at different times and different durations Sprouted nodes and flowering characteristics determined.

41 Chilling (10/15 N/D) effects on potted satsuma trees with or without fruit

42 Carbohydrate levels for trees chilled at two temperatures and fruiting or non-fruiting

43 Chilling effects on number and type of shoots

44 Effect of temperature on carbohydrate levels in non-fruiting potted trees Carbohydrates accumulated at 15/10, but not 26/20 (No results of this table discussed)

45 Effect of fruit on normal bud sprouting in field grown trees Greater numbers of nodes sprouted but fewer vegetative shoots on de-fruited trees

46 Fruit effects on carbohydrate levels in fruiting and defruited trees Very little difference in these trees?

47 Results Spring flush shoots required chilling for bud sprout while summer flush shoots did not. Mostly vegetative if no chilling Fruiting reduced vegetative shoots

48 Summary and Conclusions One table not used? Level of fruiting not stated and might have been very important Continue to show fruit suppress vegetative growth

49 Lenz, F Photosynthesis and respiration of citrus as dependent upon crop load. Proc. Intnl. Soc. Citriculture 1978;70-71 Previously found that leaf Pn may be higher near fruit than away. Translocation away from leaf or inhibition of Pn Compared fruiting and non-fruiting small trees in Germany

50 Photosynthesis and photorespiration Pn rate ml % O2 Photoresp (same parameters) Plants without fruit Plants with fruit Photoresp/Pn x

51 Pn and Photorespiration as dependent on fruit load and root temperature Temperature 12 C,Fruit-,+ 28 C,Fruit-,+ Pn rate (CO2/dm/hr) I Pn rate ( ) Expt II Photoresp Expt I Photoresp Expt II Photoresp/Pn % I Photoresp/Pn % II

52 Summary Pn higher by 63 % for leaves on trees with fruit Photorespiration only 61 % of without fruit for with fruit leaves Therefore ratio only half When root temperature changed to higher T effect of no crop on reduced Pn largely disappeared No statistics shown even though 12 replicate measurements taken

53 Albrigo, L.G. 2005) The effect of previous crop and flowering intensity on leaf area development in Valencia orange trees. (unpublished data) Invasion of citrus leaf miner resulted in questions about impact of leaf damage on different aged flushes to overall performance of citrus trees Leaf miner build-up was primarily on summer flush Hypothesis was that impact on major flush would have greater effect on tree performance Purpose: Determine amount of leaf area produced annually by different flushing periods (spring, summer, fall)

54 Materials and Methods In trees 4 years-old and 4 trees 15 yearsold were selected in two different locations, At the end of each growth flush (about 30 days), all of the new flush in 4 - ½ m 2 frames per tree was tagged. At the end of the fall flush period, all leaves were identified by age and leaf area was determined.

55 Materials and Methods Industry-wide yields were obtained from the Fla. Agric. Stat. Ser. records. Flowering potential was determined by accumulations of hours below 20 o C from the Citrus Flowering Monitor expert system.

56 Leaf area development by flushing period - Valencia % of total leaf area Year Tree Age Old Spring Summer Fall Total Leaf Area m % 15.42% 56.80% 15.86% % 36.57% 42.06% 5.32% Spring flush more in 95, but total less Average 13.99% 25.99% 49.43% 10.59% % 23.22% 48.11% 0.91% % 43.98% 29.91% 5.51% Spring flush more in 95, and total more Average 24.18% 33.60% 39.01% 3.21%

57 Crop yields year before and flower induction in same year as flush measurements Year Total flush mature % spring flush Total flush young % spring flush Past yield Current flower FBI ??? 1000 Data does not fit a reasonable pattern to past yield, maybe to FBI

58 Results The largest amount of leaf area produced in the summer More mature trees produce little leaf area in the fall in Florida in normal years Hurricane leaf and fruit loss can change that The amount of spring and summer leaf area seem to balance each other A heavy flowering reduces spring leaf area (data not shown, observational)

59 Results Leaf miner injury in the summer affects the flushes that produce the most leaf area No easy relationship between past yield of Valencia s in Florida and this leaf area development can be made from the limited data Yields should have been obtained from the trees measured