Kuliang fisiologi lingkungan ing 2014 2

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Importance of photosynthetic capacity inImportance of photosynthetic capacity in
yield determination of teayield determina...

 The basis of their argument was that leafThe basis of their argument was that leaf
yield of tea is controlled more by th...

 Moreover, the weight of harvested shootsMoreover, the weight of harvested shoots
of tea (i.e. 2-3 leaves and a bud) is o...

 Instead, tea leaf yield per unit land area isInstead, tea leaf yield per unit land area is
strongly correlated withstron...

 However, it should be borne in mind thatHowever, it should be borne in mind that
photoinhibition could reduce sourcephot...

 However, Smith et al. (1993a) argue thatHowever, Smith et al. (1993a) argue that
assimilates produced during periods ofa...

Respiratory losses ofRespiratory losses of
photoassimilates:photoassimilates:
 Respiration is the process of generatingRe...

 Tanton (1979) estimated that mature teaTanton (1979) estimated that mature tea
which accumulates biomass at a rate ofwhi...

 These respiratory losses are much greaterThese respiratory losses are much greater
than those of annual crops (i.e. 30-5...

 Because of the increase in total biomassBecause of the increase in total biomass
with time during the period between two...

 Root respiration rates increased withRoot respiration rates increased with
increasing N supply, primarily because ofincr...

 These rates varied for different years ofThese rates varied for different years of
the pruning cycle.the pruning cycle.
...

WATER RELATIONSWATER RELATIONS
 The water status of a tea plant isThe water status of a tea plant is
determined by the ba...

 Tea is generally considered to be aTea is generally considered to be a
shallow-rooting plant, sensitive to theshallow-ro...

 Nixon and Sanga (1995) also observedNixon and Sanga (1995) also observed
that the weight of fine roots with diameterstha...

 This was partly attributed to the variationThis was partly attributed to the variation
in their root systems. Earlier de...

 In another study carried out over allIn another study carried out over all
different tea growing agroclimatic regionsdif...

 However, in a similar study carried outHowever, in a similar study carried out
using five-year-old, field-grownusing fiv...

 The clones had a significantly deeperThe clones had a significantly deeper
active root zone comprising of moreactive roo...

 Mohotti et al. (2003b) have shown thatMohotti et al. (2003b) have shown that
organicallymanaged tea has a greaterorganic...

 There were associated changes in theThere were associated changes in the
anatomy of roots of 1-2 mm diameter withanatomy...

Transpiration:Transpiration:
 Water use of tea and its controlling factorsWater use of tea and its controlling factors
ha...

 A well-maintained tea canopy covers theA well-maintained tea canopy covers the
ground almost completely allowing verygro...

 In one such study, AnandacoomaraswamyIn one such study, Anandacoomaraswamy
et al. (2000) showed that both hourly andet a...

Control of transpiration by gs andControl of transpiration by gs and
shootshoot øøw:w:
 Tea has highly sensitive stomata,...

 This indicates that the rate of root waterThis indicates that the rate of root water
absorption and its subsequent trans...

 On a relatively wet soil, shootOn a relatively wet soil, shoot øwøw
recovered during late afternoon along withrecovered ...

 This stomatal reopening was probably aThis stomatal reopening was probably a
response to decreasing VPD in theresponse t...

 Interestingly, Carr (1977a) found thatInterestingly, Carr (1977a) found that
shoot øw (and therebyshoot øw (and thereby ...

 In contrast, on a dry soil, early stomatalIn contrast, on a dry soil, early stomatal
closure would have preventedclosure...

 The observation that shoot øw andThe observation that shoot øw and ggs ofs of
tea is less sensitive to Ta and VPD in ate...

 Callander and Woodhead (1981) observedCallander and Woodhead (1981) observed
that the canopy conductance per unit leafth...

Stomatal dynamics and droughtStomatal dynamics and drought
resistance of tea:resistance of tea:
 Carr (1977a) observed a ...

 Furthermore, x-axis intercept of the aboveFurthermore, x-axis intercept of the above
relationship (i.e. shoot øw at zero...

 In addition, Carr (1977a) also showed thatIn addition, Carr (1977a) also showed that
different tea genotypes can be scre...

 In a separate study, Carr (1977b)In a separate study, Carr (1977b)
identified two possibleidentified two possible
mechan...

 Moreover, the critical leaf øw forMoreover, the critical leaf øw for
significantly reducingsignificantly reducing ggs an...

 Consequently, the droughttolerantConsequently, the droughttolerant
genotype maintained a higher leaf øw andgenotype main...

 In a study comparing the water relationsIn a study comparing the water relations
of three genotypes of tea, Sandanam et ...

 In contrast, some clones were able toIn contrast, some clones were able to
keep their stomata open for a longerkeep thei...

 This strategy of keeping the stomata openThis strategy of keeping the stomata open
for a longer period during a drought ...

 Osmotic adjustment also enables a givenOsmotic adjustment also enables a given
genotype of tea to keep its stomata openg...

 Analysis of measured pressure-volumeAnalysis of measured pressure-volume
curves (Wijeratne et al., 1998b) showedcurves (...

 The lower øs at full turgor providesThe lower øs at full turgor provides
evidence for osmotic adjustment throughevidence...

 This was confirmed by the lower soil waterThis was confirmed by the lower soil water
content and soil øw at permanent wi...

 Sandanam et al. (1981) also showedSandanam et al. (1981) also showed
significant genotypic variation in thesignificant g...

Environmental factorsEnvironmental factors
controlling transpiration of teacontrolling transpiration of tea

Incident radiation and shade:Incident radiation and shade:
 When the soil is at or near saturation,When the soil is at or...

 Shade also reduces transpiration rateShade also reduces transpiration rate
primarily by decreasing the irradianceprimari...

 Some of the antitranspirants also reducedSome of the antitranspirants also reduced
transpiration by reducing the energy ...

 Wind and shelter:Wind and shelter: Some of the tea-Some of the tea-
growing regions, especially at highgrowing regions, ...

 To counter these adverse effects of highTo counter these adverse effects of high
wind speeds, wind breaks and shelterwin...

 This can be explained by basic physicalThis can be explained by basic physical
principles (Carr, 1985).principles (Carr,...

 Although Carr (1985) observed a higherAlthough Carr (1985) observed a higher
canopy resistance (canopy resistance (rrc) ...

 Moreover, during the rainy periods, theMoreover, during the rainy periods, the
higher Tc and leaf øw values of sheltered...

Transpiration efficiency and waterTranspiration efficiency and water
use efficiency:use efficiency:
 Transpiration effici...

 Stephens and Carr (1991b) obtained WUEStephens and Carr (1991b) obtained WUE
values, estimated as the slope of thevalues...

 These are lower than the TE valueThese are lower than the TE value
obtained by Anandacoomaraswamy et al.obtained by Anan...

 Although Stephens and Carr (1991a)Although Stephens and Carr (1991a)
contend that the VPD was unlikely to havecontend th...

 Stephens and Carr (1991b) furtherStephens and Carr (1991b) further
showed that WUE of tea is influenced byshowed that WU...

 The response of WUE to irrigationThe response of WUE to irrigation
increased with increasing nitrogen fertilizerincrease...

 However, as compared to the warm dryHowever, as compared to the warm dry
season, in the cool dry season, WUEseason, in t...

 WUE in the warm dry season was greaterWUE in the warm dry season was greater
than that in the cool dry season.than that ...

 WUE of tea increased with increasingWUE of tea increased with increasing
nitrogen fertilizer application, from 1.5-2.6ni...

 The above-mentioned results of StephensThe above-mentioned results of Stephens
and Carr (1990) show interesting insights...

 At lower Ta (e.g. cool dry season), WUEAt lower Ta (e.g. cool dry season), WUE
responds more to nitrogen fertilizer than...

 In contrast, under warm dry conditions,In contrast, under warm dry conditions,
water availability would be a greaterwate...

 The TE values measured in terms of kgThe TE values measured in terms of kg
ha-1 (made tea) mm-1 of water transpiredha-1 ...

 The TE and WUE values obtained by bothThe TE and WUE values obtained by both
Anandacoomaraswamy et al. (2000) andAnandac...

 Whether this indicates a greater intrinsicWhether this indicates a greater intrinsic
capacity of tea to use water moreca...

 Compiling data from several works, SquireCompiling data from several works, Squire
(1990) showed that the product TE x V...

 In addition to the environmental factorsIn addition to the environmental factors
described above, Wijeratne et al. (2007...

Effects of water deficits on tea yieldEffects of water deficits on tea yield
and yield componentsand yield components
 ::...

 The effects of water deficits on tea yieldThe effects of water deficits on tea yield
can be predicted by examining the e...

 Squire and Callander (1981) observed thisSquire and Callander (1981) observed this
limiting shoot øw to be -0.8 MPa. Sho...

 Carr et al. (1987) identified this thresholdCarr et al. (1987) identified this threshold
VPD to be around 2 kPa.VPD to b...

Influence of vapour pressure deficitInfluence of vapour pressure deficit
 Tea is one of the plant species which hasTea is...

 In addition, VPD influences these keyIn addition, VPD influences these key
processes of yield formation of tea evenproce...

 During wet periods with frequent rain,During wet periods with frequent rain,
shoot øw of tea has an inverse, linearshoot...

 During these wet periods, VPD did notDuring these wet periods, VPD did not
exceed 2 kPa and shoot øw did not fallexceed ...

 Moreover, even if the VPD decreasedMoreover, even if the VPD decreased
during the latter part of the day, shoot øwduring...

 Interestingly, when the soil was re-wettedInterestingly, when the soil was re-wetted
by rains at the end of the dry seas...

 Despite the absence of a clear relationshipDespite the absence of a clear relationship
between shoot øw and VPD during d...

Influence of increasing VPD and decreasingInfluence of increasing VPD and decreasing
shootshoot øøw on shoot growthw on sh...

 Tanton (1982a) found that theTanton (1982a) found that the relativerelative
shoot extension rate (RSER)shoot extension r...

 This reduction of RSER occurs because ofThis reduction of RSER occurs because of
the reduction in shoot øw caused bythe ...

 Furthermore, a relatively droughtFurthermore, a relatively drought
susceptible cultivar had a lower shoot øw,susceptible...

 During periods of rainfall, when VPD isDuring periods of rainfall, when VPD is
below 2 kPa, Ta is the main determinantbe...

 According to the relationships betweenAccording to the relationships between
VPD and shoot øw developed by WilliamsVPD a...

 Therefore, both shoot initiation rate andTherefore, both shoot initiation rate and
SER of tea are reduced when shoot øwS...

 Reduction of tea yields during prolongedReduction of tea yields during prolonged
dry periods have been observed by manyd...

 A characteristic phenomenon of tea is theA characteristic phenomenon of tea is the
rapid increases of yield on re-wettin...

 Re-wetting of the soil coupled with theRe-wetting of the soil coupled with the
lowering of VPD by rains quickly increase...

 While the leaf appearance rateWhile the leaf appearance rate
(1/phyllochron) is primarily related to Ta, it(1/phyllochro...

 Wijeratne (1994) also showed that theWijeratne (1994) also showed that the
phyllochron of tea seedlings grown inphylloch...

 Similarly, water stress reduced SER (fromSimilarly, water stress reduced SER (from
10.78 to 6.65 mm wk-1) and leaf10.78 ...

Critical soil water deficit andCritical soil water deficit and
response to irrigationresponse to irrigation
 The level of...

 Wijeratne and Fordham (1996) reportedWijeratne and Fordham (1996) reported
that Nsh, Wsh, shoot extension rate andthat N...

 Hence, they concluded that the criticalHence, they concluded that the critical
SWD for shoot extension should also beSWD...

 In a study which showed significantIn a study which showed significant
cultivar variation in drought sensitivity, thecul...

 Furthermore, Wijeratne (1994) found thatFurthermore, Wijeratne (1994) found that
the plastochron of tea increased withth...

 In contrast,In contrast, Othieno et al.Othieno et al. (1992) observed(1992) observed
the CSWD to be 85-100 mm for teathe...

 The feasibility of irrigation has beenThe feasibility of irrigation has been
explored as a means of countering theexplor...

 Unfertilized tea showed a lower responseUnfertilized tea showed a lower response
to irrigation with 1.4 kg ha-1 mm-1.to ...

 Field observations in Sri Lanka haveField observations in Sri Lanka have
shown that drip irrigation increased teashown t...

 For example, Othieno et al. (1992)For example, Othieno et al. (1992)
observed a yield loss of 1.3 kg ha-1 mm-observed a ...

 As expected, young tea was moreAs expected, young tea was more
susceptible to drought than mature tea.susceptible to dro...

 The lower sensitivity ofThe lower sensitivity of annualannual yields ofyields of
mature tea was primarily because it was...

 Interestingly, mature tea had four timesInterestingly, mature tea had four times
more structural roots (> 1 mm diameter)...

 Burgess and Carr (1993, 1996b) showedBurgess and Carr (1993, 1996b) showed
significant variation in drought sensitivitys...

 The drought resistant genotypes wereThe drought resistant genotypes were
able to maintain a greater crop canopyable to m...

 This is because of the contribution to wetThis is because of the contribution to wet
season yield from shoots, which are...

PARTITIONING OF BIOMASS, HARVESTPARTITIONING OF BIOMASS, HARVEST
INDEX AND YIELD 323INDEX AND YIELD 323
 Biomass partitio...

$ Particularly, the fraction of assimilatesParticularly, the fraction of assimilates partitioned to new shoots determines ...$

 Growing shoots of tea act as a strong sink forGrowing shoots of tea act as a strong sink for
photosynthates (Rahman, 198...

 In intact bushes, the carbon assimilated byIn intact bushes, the carbon assimilated by
mature leaves readily move into t...

 Older leaves do not become parasitic onOlder leaves do not become parasitic on
other leaves when they becomeother leaves...

 The photosynthetically active maintenanceThe photosynthetically active maintenance
leaves retained 19% and 25% wasleaves...

 water availability (Burgess and Carr,water availability (Burgess and Carr,
1996a), stage of the pruning cycle1996a), sta...

 However, contrary to expectations, thereHowever, contrary to expectations, there
was no observable shift in biomasswas n...

Harvest index:Harvest index:
 Harvest index (HI) plays a critically importantHarvest index (HI) plays a critically import...

 The low percentage of photosynthatesThe low percentage of photosynthates
partitioned to harvestable shoots ispartitioned...

 For a high yielding (i.e. 5600 kg ha-1 yr-1)For a high yielding (i.e. 5600 kg ha-1 yr-1)
genotype under irrigation, Burg...

 Experimental observations have shownExperimental observations have shown
thatthat fish leaf pluckingfish leaf plucking (...

 Yield:Yield: The harvested leaf yield of tea (i.e.The harvested leaf yield of tea (i.e.
made tea) can generally reach 4-...

 Even at these upper limits, tea yields areEven at these upper limits, tea yields are
much lower than the 10-20 t ha-1 yr...

 Both climatic and soil constraints wouldBoth climatic and soil constraints would
reduce tea yields from their upper limi...

RESPONSE OF TEA TO CLIMATERESPONSE OF TEA TO CLIMATE
CHANGECHANGE
 Long-term gradual climate changeLong-term gradual clim...

 Because of the close relationshipsBecause of the close relationships
between tea yield and these atmosphericbetween tea ...

 Responses to different aspects of climateResponses to different aspects of climate
change can be both positive and negat...

 However, there can be substantialHowever, there can be substantial
genotypic variation in the response togenotypic varia...

nine-month-old tea seedlings of onenine-month-old tea seedlings of one
genotype (TRI 3019) increasedgenotype (TRI 3019) in...

 In two CO2 fertilization field experimentsIn two CO2 fertilization field experiments
carried out over a period of 18 mon...

of 370 μmol mol-1 to 600 μmol mol-1 (whichof 370 μmol mol-1 to 600 μmol mol-1 (which
is predicted to occur during the midd...

 Increases in both Nsh and WshIncreases in both Nsh and Wsh
contributed to these yield increases.contributed to these yie...

 The study of Wijeratne et al. (2007b) alsoThe study of Wijeratne et al. (2007b) also
identified several climate change-i...

 Similarly, a quadratic relationship wasSimilarly, a quadratic relationship was
found between monthly tea yield andfound ...

 However, at low altitudes, yield gains ofHowever, at low altitudes, yield gains of
higherhigher CCa were pulled back bec...

 Table 4.Table 4. Projected tea yields at fourProjected tea yields at four
locations in Sri Lanka under differentlocation...

 Location characteristics: altitude (m a.s.l.)Location characteristics: altitude (m a.s.l.)
maximum/minimum temperature, ...

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