Chapter 8 - Physical cues for growth and reproduction

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Adaptation of termperate plant, peach, to cropping in the subtropics. This variety, Flordaking, has been bred with reduced dormancy which confers a 'low chill' requirement. This allows the reproductive cycle to proceed at latitudes (29° in this instance) where winters are insufficiently cold to break the deeper dormancy of normal 'high-chill' varieties. Developing flowers were excised from within the protective bud scales over a period from early autumn (March, left) to midwinter (July, right) and show continued slow growth throughout.

(Photograph courtesy J.J. Lloyd and C.G.N Turnbull)

Amongst other fundamental properties, the protoplasm of plants is endowed with that of irratability, a certain sensitivness, that is, to the influence of external agents

(Sydney Howard Vines, Lectures on the Psychology of Plants, 1886)


On the one hand, the farmer is concerned with the living plant; on the other with that complex set of factors we call the environment ... A plant, like an animal, is a sensitive living thing. Plants make responses to their environment [which] ... may be expressed in tons of leaves and stems, in tons of roots, in pounds of seed or grain, in barrels of fruit, or in percent of sugar, or starch, or acid ... First, we must understand something of the structure and functions of the plant. Second we must have a knowledged of the various factors of the environment. And third, we must know the manner in which the plant behaves under a given set of conditions. This is a big order. It is asking much.

(Wilfred W. Robbins, Principles of Plant Growth, 1927)