Interrelationships of vegetative growth and assimilate distribution of Citrus limettioides seedlings in response to root-applied GA₃ and SADH

Abstract

The effects of root-applied GA3 or SADH on vegetative growth, distribution of 14C-labelled assimilates, and starch content of various organs of Citrus limettioides seedlings were investigated. In contrast with the uniform elongation rate of control seedlings, GA3 induced an initial high elongation rate which later dropped to the level of the control, resulting in considerably longer seedlings. Final leaf area was drastically reduced by GA3 root treatment, which also induced both earlier appearance of thorns and more and shorter thorns per seedlings. Elongation rate of SADH-treated seedlings was initially retarded, but vigorous growth was later resumed for a short period, causing treated seedlings to be eventually similar to, or slightly longer than, controls. SADH did not affect the number and timing of thorn emergence but considerably promoted their elongation.The effect of GA3 and SADH on the vegetative growth was closely related to their differential effects on distribution of assimilates and starch in shoot and root tissues. A high growth rate was characterized by an increased supply of 14C-labelled assimilates to shoot organs and especially to buds as well as by a greater utilization of starch. The opposite was found in the root system, resulting in a significant modification of shoot–root ratios of both 14C-Iabelled assimilates and starch. The changes in 14C-labelled assimilates and starch usually preceded changes in growth, thus suggesting that GA3 and SADH effects on growth are mediated via their effects on the activity of apical sinks.

Transport and metabolism of xylem cytokinins during lateral bud release in decapitated chickpea (Cicer arietinum) seedlings

“…Data were then corrected for the weights of different samples of tissue, to allow estimation of labelling intensity. Because absolute amounts of recovered label varied slightly among experiments, data were recalculated to give a specific labelling index (SLI) on a tissue weight basis as described by Ben‐Gad et al. (1979) whereby:…”

Enhanced inflorescence development in tomato by growth substance treatments in relation to 14C‐assimilate distribution

“…The radioactivity in the various parts of the plants was expressed either as a percentage of the "C translocated out of the source leaf or using the Specific Labelling Index (SLI) calculated as follows: radioactivity in a given part, expressed as a percentage of the total '*C translocated out of the source leaf, divided by the dry weight of the given part, expressed as a percentage of the dry weight of the whole plant excluding the source leaf (Ben-Gad et al 1979). The first-mentioned measure is strongly influenced by the size of a plant part relative to the size of the whole plant.…”