Growth and Development of Horticultural Crops (1+1)

Translocation rates

• The rate of movement of compound is controlled by the rate of acceptance by sink
• The rate of movement of substance is measured by labeled isotopes 14C, 32P, 40K, 55Fe, 45Ca.
• Phloem size seems to develop according to the size of the source or sink it serves. Size and volume of phloem limits the flow from source to sink
• Larger the leaf area larger is the cross-sectional phloem area.
• Translocation rate differs among the species of crop plant in C3 &C4 plants
• Leaves of C4 plants have higher CER than C3 plants
• The improved export of assimilates in C4 plant may be due to Krantz anatomy
• Bio molecules in the signaling pathways have greater role in the source sink relations.
However there is evidence to indicate that improved export might be related more to higher CO2 exchange rates than to leaf anatomy. Phloem loading & unloading can be rate limiting & can affect translocation.