Plant growth co-ordination in natura: a unique temperature-controlled law among vegetative and reproductive organs in mango
Résumé
The impact of temperature on plant growth is usually studied on the leaves of annuals. We studied in natura the effect of temperature on the growth of three plant organs: the growth unit (GU) axis; its attached leaves, considering their position along the axis; and the inflorescence axis. Mango tree was chosen as plant model. Organ growth was measured at different seasons and elevations, permitting a range of temperatures overlapping the optimal range for mango growth. Four growth parameters were investigated: the final organ size, the duration of growth, the maximal absolute growth rate (AGR(max)) and the relative growth rate at the time of AGR(max) (RGR(ip)). Temporal growth dependencies were found between the axis and its leaves, regardless of their positions. Size dependencies were revealed only between the GU axis and its proximal leaf. Strong effects of temperature on duration of growth and on RGR(ip) were observed regardless of the organ studied. A common allometric coefficient linked duration of growth and RGR(ip) of all organs although the intercepts for axes and leaves were different. These relationships strongly suggested that regardless of the physiological mechanisms subtending the growth dynamics, e.g. auto- vs heterotrophy, a common temperature-controlled allometric constraint is probably underlying the growth of all these organs in mango.