Study On Photosynthetic Characteristics Of Three Young Plums (Prunus)

Photosynthetic characteristics of two-year Gulf ruby (Prunus salicina Lindl.), Purple plum (Prunus domestica Lindl.) and Black amber (Prunus salicina Lindl.) grafted on Amygdalus persica Lindl. were comparatively investigated by Licor-6400 photosynthesis portable in field from March, 2003 to November, 2003. Effects of physiological and zoological factors such as light, temperature, concentration of carbon dioxide, age of leaves, position of leaves and concentration of chlorophyll on photosynthesis were measured. The results were briefly summarized as follows:1. Comparative research on net photosynthetic rate (Pn) of the three plums was processed in a fine day, somber day and nubilous day . Response curves in a fine day took on two-peak pattern, the first (bigger) peak reached at 9:00 10:00, and the second (smaller) at 15:00 16:00. In a somber day diurnal variation of Pn presented one-peak pattern, and in a nubilous day presented anomalous two-peak pattern.purple plum and Black amber had higher Pn than Gulf ruby.2. Monthly and double monthly Pn were measured. Response curves presented two-peak pattern with the first peak on May 30th and the second peak on September 25th. The lowest point reached in mid-July. The day time of the first peak changed every month.Purple plum and Black amber had higher Pn than Gulf ruby.3. The Pn increased quickly with argument of light strength in the condition of weak light, while slowly in the condition of strong light. Too strong light inhibited photosynthesis. The light compensation points of the three trees were 40.8⁶6, 46.8 50.4, 45⁵7 (umol m-2 s-1) respectively, and the saturation points were 2000²800, 1800²600, 2200-2600(umol m-2 s-1). The apparent photosynthetic quantum yields (AQY) were 0.0325-0.0424, 0.0451-0.0493, 0.0436-0.0442 respectively.4. The Pn increased quickly with the hoist of concentration of carbon dioxide in the condition of low concentration. But in the condition of high concentration, the increase was slow, and even too high concentration inhibited photosynthesis. In a short, the response curves between Pn and carbon dioxide almost accorded with parabolas. The carbon dioxide compensation points of the three trees were 30.55⁶3.00, 33.70⁷3.00, 38.95⁴6.20(umol mol-1) respectively which became bigger with increase of light or temperature. The carbon dioxide saturation points were 1200 - 1750, 1100 1400, 1200 1400(umol mol-1). To compare,Purple plum and Black amber had higher carboxylation efficiency (CE) and photosynthetic capacity (Pm) than Gulf ruby.5. The Pn of plums accorded with parabolas with the change of temperature. Theiroptimum temperatures were 26C, 28.5C, 30³1C respectively. Their low temperature compensation points were 11.5C, 15C, 12¹3C, and high temperature compensation pints 40.5C, 42C, 49⁵0C. The high temperature inhibited photosynthesis lay in argument of mesophyll inhibition.6. The Pn of leaves from tip to bottom in comparable tresses increased at the beginning and then decreased. The change of Pn of Gulf ruby and Purple plum accorded with parabolas, while Black amber accorded with quartic equation. The positions of leaves of their most Pn were the 13-15th burl, the 7-10th burl, the 7-8th burl respectively. The ages of the most Pn were about the 35th day, the 18¹9th day, the 15 16th day respectively. Reaching critical point Pn from minus to plus needed three or four days. _<sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub><sub>7. The changes of Pn and chlorophyll a/b with the ages of leaves both accorded with quartic equation. The positive relativity between Pn and chlorophyll a/b was manifest at early ten days but blurry later. The content of chlorophyll a, b and carotenoid increased with the age up. In the first ten days, they increased quickly, afterwards, slowly. The chlorophyll a increased more quickly.8. The palisade tissue and spongy tissue of Gulf ruby were both thinner than those of Purple plum and Black amber. But the epidermis of Gulf ruby w...