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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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