source sink nra
TRANSCRIPT
PARTISI BIOMASSA
(SOURCE – SINK RELATIONSHIP)
Plant systems = Fabric systems Kinerja sistem tanaman dalam
menghasilkan biomassa total tanaman berhubungan dengan
(i) aktivitas daun menghasilkan fotosintat
dengan CO2 dan energi radiasi sebagai
bahan baku, (ii) aktivitas metabolisme mensintesis biomassa dengan fotosintat sebagai
bahan baku utama
Biomass, W
Met
abol
ic P
roce
ss
Photosynthetic process GRO
WTH
MAC
HIN
ERY
INPUTS PLANT GROWTH
PROCESS
OUTPUTS
CH2O
Fase Perkembangan
LD
Suhu Cahaya
Efisiensi Fotosintesis
BM Daun
BM Akar
BM Biji (Q) BM
Batang
P G
F Laju
Rm
Produktivitas tanaman (yield) adalah puncak dari berbagai proses yang terjadi dalam suatu siklus tanaman
Produktivitas tanaman ditentukan oleh kemampuan tanaman berfotosintesis dan mengalokasikan sebagian besar hasil fotosintesis ke bagian yang bernilai ekonomis
Sistem dikatakan efisien apabila :
Ukuran dan struktur kanopi dpt maksimal mengintersepsi cahaya dan CO2
Kapasitas organ pengguna (biji) cukup menerima fotosintat
Penerimaan BM organ pengguna tidak melebihi dari yang diperlukan untuk mendukung tingginya efisiensi.
Suplai nutrisi mineral dan air cukup
Photosynthesis
Biochemical processes to produce carbohydrate from water and carbon dioxide using light energy.
Simple reaction equation: H2O + CO2 + Light energy →
(CH2O) + O2
Partisi atau pembagian biomassa tanaman merupakan salah satu faktor yang menentukan hasil akhir tanaman seperti berat biji
Untuk produksi biomassa yang sama, semakin banyak biomassa yang dialokasikan ke bagian yang dipanen (biji), semakin tinggi produk akhir tanaman.
Sink-source relationship
Source is a net exporter or producer of photoassimilate; it exports more assimilate than it requires for its own.
Sink is a net importer or consumer of photoassimilate.
Photoassimilates are translocated from a source to a sink.
Organ tanaman yang dapat memfiksasi CO2 disebut source
Daun dan semua jaringan tanaman yang berfotosintesis adalah source
Sink adalah semua bagian tanaman yang tidak berfotosintesis atau berfotosintesis tetapi tidak maksimum sehingga sebagian kebutuhan karbohidratnya disediakan oleh source
Hubungan source-sink tanaman penting dalam memahami produktivitas dan management tanaman selama periode pertumbuhan
Figure 1. Source to sink relationships at two stages of cotton growth. During early vegetative growth, most of the carbohydrates produced by the leaves are sent to the root system. Later in the season, how-ever, most of the carbohydrates are sent to the developing bolls, and the root system and shoot growth rate decline.
Allocation and partitioning Allocation = the regulation of the
distribution of fixed carbon into various metabolic pathways (i.e. the fate of fixed carbon) - includes storage (starch), utilization (metabolic energy, synthesis of other compounds), and synthesis of transport sugars
Partitioning = the differential distribution of photosynthates within the plant
- various sinks partition sugars- distribution must be balanced- many cultivars are economically important because they partition to edible plant parts (fruits, grains)
Efficiency of crop production Harvest Index = (Dry mass of
harvestable organs)/(Total dry mass of the plant)
Transplants, leafy vegetables : Net photosynthetic rate ≈ whole plant
growth rate ≈ yield Fruiting vegetable production, root
crops : Net photosynthetic rate ≈ whole plant
growth rate ≠ yield
Understanding mechanisms of translocation of photosynthates (carbohydrate) is critical
Mechanism of translocation in the phloem
Pressure-flow hypothesis: Sugars are translocated in the phloem by mass transfer along a hydrostatic (turgor) pressure gradient between the source and sink.
Phloem loading and unloading play a major role in regulating both translocation rate and partitioning of assimilates between competing sinks.
Assimilate distribution (allocation and partitioning)
Regulation of assimilate distribution affects productivity and yield.
Plant microenvironments should be controlled so as to enhance more assimilate distributed to harvestable organs.
Allocation of assimilate in leaves Leaf metabolism and biomass Storage Export from the leaf
Partitioning of assimilate among sinks
Sink strength Distance between sink and source
NOTE: If the number of sinks is reduced, a correspondingly higher proportion of the photoassimilates is directed to each of the remaining sinks. Idea of fruit pruning is based on this.
Sink strength
Idea to express capacity of a sink to accumulate metabolites. It is often given as the product of sink size and sink activity, as follows:
Sink Strength = Sink Size X Sink Activity
However, it is a conceptual value and not actually well quantified.
Distribution of photoassimilates in plants (Marshall and Sager, 1976)
Soy beans Potato Tomato Wheat
Sink competition
Flowering young tomato plants roots>young leaves>in-florescence
Fruiting tomato plants fruits>young leaves>flowers>roots
(Ho,1988)
Sink tissues compete for available translocated photosynthates Example: young leaves compete with
roots for photosynthates In sugar beet and bean: - Over short term: rates of photosynthesis and
export from single source do not change; young leaves receive relatively more sugar than roots
- Shading decreases partitioning in roots
- Young leaves can deplete sugar content of sieve elements more rapidly, thus increasing the pressure gradient and translocation toward themselves
Environmental influences on partitioning
• Water stress – More root growth • Nitrogen – High N supply…less root growth – Low N supply…more root
growth
Partitioning of photoassimilates in plant
1 Relationship between sink and source
• Sink-source is variable: • Young leaf—sink, half-developed leaf—
sink and source, well developed leaf— source. • Developing seed, tuber—sink;
germinating seed—source
(2) Sink-source are promoted and inhibited by each other.• Small source→small sink , small sink inhibits source activity. Such as shading leaf , grain number↓ , empty↑ , small fruit.• Too strong source makes sink ↓ and too strong sink results in source activity and causes premature of source.• “Full source , large sink and high transloaction”——high yield physiology.
Konsep keseimbangan source-sink
Apabila kapasitas source > potensi kapasitas sink, maka laju produksi BM dikendalikan oleh source
Apabila kapasitas sink > potensi kapasitas source, maka laju produksi BM dikendalikan oleh sink
Evidences of Sink-Source interaction
-Partial or complete removal of sink organ (i.e. fruits) reduced leaf photosythesis
- Partial removal of source organ (leaves) while remaining fruits load increased the remaining fruits load increased the remaining leaves photosynthesis
A diagram of pressure flow(a driving force oftranslocation ofphotoassimilates
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Unloading
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PENDEKATAN MEKASNISTIK
Bagaimana cara menganalisis partisi biomassa (mis. ke biji)?
INDEKS PANEN =HARVEST INDEX (HI)
Indeks panen (IP) = harvest index (HI) : kemampuan tanaman menyalurkan asimilat ke bagian ekonomis, tanpa satuan
Harvest index, the ratio of grain weight to total plant weight
HI reflects the partitioning of photosynthate between the grain and the vegetative plant.
Indeks panen (HI) dari beberapa jenis tanaman
Jenis tanamanJenis tanaman VarietasVarietas W (Mg/ha)W (Mg/ha) HIHI Umur (hari)Umur (hari)
Padi sawahPadi sawah IR36IR36 13,913,9 0,490,49 107107Padi gogoPadi gogo IR36IR36 14,314,3 0,330,33 118118GandumGandum Acc. No. 4073Acc. No. 4073 8,58,5 0,310,31 8484JagungJagung UPCA Var. 1UPCA Var. 1 15,615,6 0,390,39 9898SorghumSorghum B8417B8417 14,614,6 0,480,48 9090KedelaiKedelai Clark 63Clark 63 6,46,4 0,470,47 8484Kacang tanahKacang tanah MoketMoket 8,18,1 0,360,36 112112Ubi jalarUbi jalar Georgia RedGeorgia Red 10,410,4 0,600,60 126126
Harvest index (HI)
HI = grain yield / biological yield Biological yield = grain yield + stover
yield
Corn: 0.50 to 0.55
Wheat: 0.40
Soybean: 0.40 to 0.45
Sorghum: 0.48
Balanced use of inputs like seed, fertilisers and moisture is essential for improving HI of grain plant
Characteristics like high seed germination percentage, physical and genetic purity, vigour and viability are important to optimize crop HI
Kesimpulan Indeks panen (HI) berhubungan dengan
biomassa tanaman, dan HI mula-mula meningkat pesat dengan peningkatan biomassa tanaman, tapi kemudian meningkat perlahan dan akhirnya relatif konstan dengan peningkatan biomassa lebih lanjut.
HI merupakan parameter yang dapat digunakan untuk mempelajari distribusi biomassa ke bagian yang dipanen (biji).
Jumlah biomassa yang dialokasikan ke bagian yang dipanen kurang dari 50% dari biomassa total tanaman untuk beberapa jenis tanaman
PHLOEM PHLOEM TRANSPORTTRANSPORT K plays a critical role in phloem K plays a critical role in phloem transporttransport
SourceSource
SinkSink
KK
The law of assimilate partition• 1. Source to sink prior to growth center• Growth center is a part growing fast and getting assimilate easily at that time.
(2) Same position transport, neartransport prior to the sink next to source.
Keep flag leaf !
2. Ipsi-lateral transport, near supplicationprior to the sink next to source.Maintaining flag leaf and fruit leaf!
3.3 Redistribution and reutilization of assimilate• Transport from senescence leaf to young part and from vegetative organ to reproductive one.
Factors affecting assimilatetranslocation 5.1 Internal factors • 1. Sucrose content:
S↑ , export↑. 2. ATP↑ 、 Pi↑ , TP↑ , export ↑. 3. Plant hormones:
IAA 、 GA 、 CTK ↑ , import ↑ • 4. Size in sink , sink ↑ , import
↑
4.2 Environmental factors• 1.Water: not enough, water potential↓Pn↓ , S↓ , resistance↑ , transport↓.• 2. Light: light↓ , Pn↓ , S↓ , export↓• Transport during daytime>one at night
3. Temperature : optimum 20-30℃. T↓ ,transport↓ because of respiration↓ ,energy↓ , Pn↓ photoassimilate↓ ,viscosity↑ , callose ↑.• High T , transport↓ , due to respiration↑ , Pn↓ , photoassimilate↓ ,viscosity↑ , callose ↑• Larger difference in temperature favorstransport because of accumulation ofphotoassimilate.• 4. Mineral nutrition , B 、 P 、 K.
Table 1 Effect of heat events on the harvest index of T. aestivum cv. Chablis (after Wollenweber et al. 2003).
Values are given as means (n=30). Within a column, means
followed by the same letter are not significantly different at the p=0.05 level, using the Tukey test. Heat events (HT) were induced during the double-ridge stage (DR; 25 °C) and/or anthesis (AN; 35 °C).
treatments main tiller side tillers
control (no HT) 0.52 a 0.43 b
HT at DR 0.54 a 0.48 a
HT at AN 0.34 b 0.30 c
HT at DR+AN 0.31 b 0.29 c