Ludlow College, Ludlow, England
As a young man, Knight had some education at Ludlow grammar school (now Ludlow College), but he learned more by observing and asking questions in the gardens at his home.
Balliol College, Oxford, England
Knight graduated from Balliol College, Oxford.
Hereford Museum and Art Gallery, Hereford, England
Portrait of Thomas Andrew Knight, holding an Oak branch, dated January 1837, by Edmund Ward Gill.
1805
Royal Society, London, England
Knight was elected a Fellow of the Royal Society in 1805.
1804
Royal Horticultural Society, London, England
When the Horticultural Society was founded in 1804 Knight was a member, and from 1811 he was its president.
1805
Royal Society, London, England
Knight was elected a Fellow of the Royal Society in 1805.
Balliol College, Oxford, England
Knight graduated from Balliol College, Oxford.
Ludlow College, Ludlow, England
As a young man, Knight had some education at Ludlow grammar school (now Ludlow College), but he learned more by observing and asking questions in the gardens at his home.
Royal Horticultural Society, London, England
When the Horticultural Society was founded in 1804 Knight was a member, and from 1811 he was its president.
Hereford Museum and Art Gallery, Hereford, England
Portrait of Thomas Andrew Knight, holding an Oak branch, dated January 1837, by Edmund Ward Gill.
https://www.amazon.com/Selection-Physiological-Horticultural-Papers-Microform/dp/1356468004/?tag=2022091-20
1841
Botanist horticulturalist scientist
Thomas Andrew Knight was born on August 12, 1759, near Ludlow, Herefordshire, England. He was born into an old Shropshire family with independent means and a substantial estate. His father, Thomas Knight, died when he was young; his elder brother, Richard Payne Knight, the numismatist, helped him by establishing him at Elton with a farm and hothouses, and later by handing over to him the management of 10,000 acres at Downton Castle, his home in Herefordshire.
As a young man, Knight had some education at Ludlow grammar school (now Ludlow College), but he learned more by observing and asking questions in the gardens at his home. He graduated from Balliol College, Oxford.
Attention was first called to his work in 1795 by the publication of the results of his research into the propagation of fruit trees and the diseases prevalent among them. He used 10,000 acres of land he inherited to conduct breeding of plants including strawberries, cabbages, and peas and built an extensive greenhouse. In 1797 he published his Treatise on the Culture of the Apple and Pear, and on the Manufacture of Cider and Perry, a work which passed through several editions. He was one of the leading students of horticulture in the eighteenth and nineteenth centuries, but his personal papers disappeared after his death.
His first published letter to Sir Joseph Banks was on the gradual decline of stock propagated by grafting and the need to develop new varieties from seed, particularly by cross-fertilization. The latter would produce both greater vigor and a wider range of offspring from which the most useful could be chosen.
For practical purposes, he bred apples, pears, and Herefordshire cattle, but he also worked from 1787 on peas selected as suitable because they were annuals with clearly differentiated paired characteristics. In a paper of 1799, he described how in the crossing of a gray pea with a white pea all the first generation are gray, but the white reappear in the second generation. He had observed dominance, but had done none of the careful statistical work that made Mendel’s experiments of half a century later so significant.
Thomas Andrew Knight went down in history as one of the most prominent British horticulturalists of the 18th century. His most important contribution to horticulture and agriculture was in the application of scientific principles and techniques to practical situations of the grower or breeder. He worked on the design of hothouses, control of pests, and cider making as carefully as he did on theoretical research.
Study of the developing fruit led Thomas Knight to design careful experiments on the translocation of sap. He used colored infusions to trace the ascent of sap through the outer layers of alburnum (xylem), branching to petioles and passing to the developing fruit; he also used ringing to trace the descent of sap, disproving Hales’s theory that bark was formed from the alburnum. He believed that the sap circulated, but showed that sap in the bark differs from aqueous sap in the alburnum, as a result of nutrients received from the leaves. If leaves were shaded the quantity of alburnum deposited was small. He discussed at length the forces causing this circulation, certain only that the explanation must be mechanical. He knew of capillarity and demonstrated transpiration and observed the spiral vessels, but he took no account of root pressure or cohesion of liquid columns, so he suggested a process involving the contraction and expansion of “silver grains.”
His most famous work was on what are now called geotropisms. In a letter read by Banks to the Royal Society in 1806, Knight described how he eliminated the influence of gravitation on germinating seeds: he attached them at various angles to the rim of a vertical wheel which was driven by a stream in his garden to revolve continuously at a rale of 150 r.p.m. As the germinating plants grew, each shoot was directed to the center of the wheel; when a shoot passed the center of the wheel its tip turned back so that growth was still centripetal; the roots grew away from the center. Next, he set up a similar structure with the wheel horizontal and rotating at 250 r.p.m. so that the seedlings were influenced by both gravitation of the earth and the centrifugal force. In this case, growth was at an angle of 80° to the vertical, the shoot upward and inward, and the root downward and out. Reducing the rotation to 80 r.p.m. decreased the centrifugal force to such an extent that the plants grew at an angle of 45° to the vertical.
Here he ran into the philosophical problem of how the plants “perceived” the force acting on them, as he was himself “wholly unable to trace the existence of anything like sensation or intellect in the plant.” Yet these seedlings clearly reacted to the gravitational force, for he had shown in 1801 that vine leaves always move so as to present the upper surface to the sun; and in 1811 he was to demonstrate that in certain conditions roots may be deflected from the vertical by moisture. The plants were making adaptive responses, but his explanation was typically mechanical: the roots bend down by their own weight, while in the shoot, nutrient sap moves to the lower side and there stimulates differential growth and curvature to the vertical. He was aware that this was not entirely satisfactory as he had not explained the “weeping” tree.
Knight was elected a Fellow of the Royal Society in 1805. When the Horticultural Society was founded in 1804 he was a member, and from 1811 he was its president.
In 1791 Knight married Frances Felton. They had a son who died in youth and three daughters.
