Research On Photosynthesis Characteristics Of Alnus Cremastogyme Burkill In Two Plantation Age

Transpiration and other physiological diurnal variation, seasonal variation, differences in orientation, light responses of the 4 years old and 9 years old Alnus plantation photosynthesis were studied by Li-6400, the main results are as follows:(1) Both plantation Alnus net photosynthetic rate (Pn) of the diurnal variation showed a single peak and double peak changes of the two, but even with a curve type, time of peak is not the same, or there Pn the same time as the peak size is different, maximum value between the hours of 10:00 to 12:00.4 years old seasonal variation of Alnus Pn a single peak, the peak in July, were 8.97μmol·m-2·s-1,7.95μmol·m-2·s-1,9 years old seasonal variation of Alnus Pn for the two peaks, the larger peak in July, another peak in November. Both plantation orientation Alnus 4 Pn values (truck) size in all seasons, no obvious order of regularity, bearing annual average from the point of view both plantation Alnus Pn are larger at south,4 year-old Alnus Pn lower at west, and 9 years old Alnus's minimum Pn are at the east. Overall, Pn diurnal variation, seasonal variation curves and orientation can be reflected in annual Pn values:the lower leaves than upper leaves have a stronger photosynthetic capacity; 4 years old Alnus have stronger photosynthetic capacity than 9 years old ones.(2) The lower and upper leaf of two forest age Alnus transpiration rate (Tr) of the diurnal variation and diurnal variation of Pn similar, showing a single peak and double peak variation, most of diurnal variation of Tr is a single peak type, and the maximum Tr behyond 5 mmol·m-2·s-1, that is light Alnus Transpiration water consumption of plants, to water demanding.4 years of lower seasonal variation of leaf transpiration rate is two peaks, and the others are single-peak curve, and the maximum is in July. Both plantation Alnus's Tr values in all seasons had no regularity in the four direction, from the annual average position of view both plantation north of Alnus are the largest and the east is the smallest. Generally, the upper leaves have a stronger ability to transpiration than the lower leaves; 4 years Alnus's transpiration stronger than 9 years old ones.(3) The lower and upperleaf of two forest age Alnus, water use efficiency (WUE) of the diurnal variation also showed a clear single peak and double peak variation, diurnal variation curve of the double peaks, and were in various parts of water use efficiency than the morning session afternoon session, the highest value in more than 8 am and 10 pm,4 pm and 6 pm at the lowest WUE.4 years old Alnus upper and lower parts of leaf water use efficiency on the mean size of the order of April> July> October> november,9 years old Alnus water use efficiency on the mean seasonal variation curves for the double peaks, peaks in July and November. In the east,4 years of annual mean WUE than Alnus 9 years old, and in the south, west, north,9 years old Alnus annual average of more than 4 years of WUE Alnus. In general, the upper part of the higher water use efficiency of leaves in the lower leaves,9 years old Alnus higher water use efficiency in Alnus 4 years.(4) Both plantation Alnus's Pn are enhanced with increased light intensity, Pn rising fast when the light intensity below the 600μmol·m-2·s-1, Pn growth slowly when it reached 800～1500μmol·m-2·s-1, fundamental to maintain a constant value,4 years old Alnus have a higher photosynthetic efficiency than 9 years old Alnus at the same light intensity. Ci decreased when both plantation in the light intensity below 1000 mol·m-2·s-1, and Ci begin to rise when light intensity reached 1200 mol·m-2·s-1, Ci of 9 years old Alnus are greater than 4 years old ones in the same PAR. Cond rised with light intensity increased,4-year-old Alnus intercellular CO2 concentration (Ci) are greater than 9 years old ones at the same PAR. Both plantation transpiration rate (Tr) is positively correlated with PAR, Tr values of 4 years old Alnus are greater than 9 years old ones. Both plantation water use efficiency (WUE) increased with the upward trend in PAR's, WUE increased slowly when the PAR reached 800μmol·m-2·s-1,9 years old Alnus water use efficiency (WUE) is greater than 4 years ones at the same light intensity.