14.7 Concluding remarks

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Vascular plants have come to occupy virtually every stable niche on earth during the course of their evolutionary history, regardless of thermal regime, and with remarkable adaptive capacity to acclimate to heat and cold. Plants may not necessarily thrive under extreme conditions, but they do at least exist, and are able to achieve a positive carbon balance and complete their life cycles due to physiological mechanisms and morphological features that lend thermal resilience.

Temperature extremes, especially in combination with other environmental stresses, impose an intense selection pressure. Cycles of vegetative growth and reproductive development have become closely attuned to such conditions, especially where growing seasons are brief and dormancy protracted. Such genotypes thus become highly specialised in their thermal responses.

Under more moderate conditions, survival mechanisms are of less importance and temperature assumes a different role in shaping genotypes by setting the biological tempo of ecosystems. Growth rate and reproductive effectiveness then become paramount, and again a genotype × environment interaction is apparent in the direction of biological responses due to temperature effects on carbon gain and reproductive development. An appreciation of processes underlying such responses lends a new dimension to our appreciation of natural ecosystems and our management options for communities of cultivated plants.