Root Growth as a Factor in the Response of Pisum sativum L. to Irrigation

Abstract

A WATER shortage at any stage of plant growth usually results in a reduction in vegetative growth, but many annual crop plants are especially sensitive to changes in soil moisture conditions during the period from flower initiation to the development of full flower1–3. It has been shown that during this period shortage of water has a maximum depressive effect, and irrigation has a maximum beneficial effect, on the yield of seed and fruit. Pea plants (Pisum sativum L.) respond in this manner, and while soil moisture conditions during the period from sowing until the start of flowering have little influence on final yield of peas1,4, this crop is particularly responsive to irrigation at the start of, or during, flowering1,4–6. Later, at the flat-pod stage of growth, the plants again appear to be insensitive to soil moisture conditions, but they respond to irrigation when the pods are swelling4. Both Muhleisen7 and Salter4 have analysed the effects of irrigation at flowering on the components of yield and demonstrated that the increase in yield occurred through an increase in the number of seeds set per pod and pods set per plant. The reasons why plants should be so sensitive to soil moisture conditions during flowering, however, have not been satisfactorily determined. Brouwer1,5 suggested that the beneficial effect of irrigation at flowering arose from the increased availability of nutrients brought about by the increased water supply.