Page 148 - FRUTAS DEL TRÓPICO

148 Frutas del trópico

Figura. 1. A portable infrared gas analyzer for measuring photosynthesis, transpiration,
stomatal conductance and internal CO2 content of plants.

Measuring net CO assimilation of leaves has often been used as an indicator of plant
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stress to various biotic or abiotic factors prior to any visible signs of damage. For example,

Figure 2 shows a comparison of the effect of flooding on net CO assimilation of ‘Gefner’
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atemoya on flood-tolerant (A. glabra) and flood-sensitive (A. squamosa) rootstocks. After 3

days of flooding, net CO assimilation was significantly lower for atemoya on a flood-sensitive
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rootstock than on a flood-tolerant rootstock, although visually there was no difference in vigor

between the plants of different rootstock. Therefore, measuring net CO assimilation allowed
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very early detection of flooding stress prior to the occurrence of any visual symptoms.

Transpiration (E or Tr) is the rate at which H O is leaving the leaf. Factors that affect
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transpiration include relative humidity and temperature which affects the vapor pressure de-

ficit (VPD; the difference in vapor pressure between leaf and surrounding air). This is the for-

ce that drives transpiration. Evapotranspiration (ET) is the transpiration + evaporation from

soil. Transpiration usually accounts for most of the ET (about 80-90% is from transpiration).

Universidad Autónoma de Chiapas