The Physiological Performance In The Inverted Senescing Process Of Wheat Leaves

The kernels of the wheat are filling milk accompanied with senescence of the leaves.Prolonging the leaf functional period, delaying the senescence time of the leaves andpreventing the premature senility are the problems which the scientists are always consideringabout. The discovery of the inverted senescing sequence wheat supplies the possible solutionto this question. When talking about the inverted senescing sequence wheat, the colour of flagleaves turned yellow earlier than the penultimate leaves, bringing other physiological andecological differences from the normal senescing sequence wheat. The results are as follows:1. The variations of chlorophyll content were closely related to the inverted senescing ofthe wheat. The phenomenon of chlorophyll content inverted senescing took place at18d afteranthesis. At that time, the chlorophyll content of the flag leaves were lower than thepenultimate leaves; meanwhile, the chlorophyll content of the flag leaves stayed higher thanthe penultimate leaves until the mature period in the normal senescing sequence wheat.2. The variation time of the net photosynthesis rate and the stomata conductance was outof sync with that of the chlorophyll content. The inverted senescing of net photosynthesis rateoccurred later, and the inverted senescing of stomata conductance occurred at the time nearingthe mature period.3. The chlorophyll fluorescence parameters of the flag leaves also had the phenomenonof inverted senescing. The inverted senescing of ФPSⅡactual photochemical efficiency, PSⅡ latent activity (Fv/Fm) variations, heat dissipative quantum ratio (Fo/Fm) occurred at thesame time with chlorophyll content variations. However, after a stable stage, the maximumphotochemical efficiency (Fv/Fm) began to change.4. The variations of catalase (CAT) activity presented a fluctuant tendency. After atransitory peak, the figure decreased rapidly, appearing the flag leaf of catalase (CAT) activitylower than penultimate leaves.5. Malondialdehyde (MDA) content in the flag leaves increased first, and then with the degree of senescing deepening, the figure rised sharply, higher than the penultimate leaves.The whole process was nearly the same as the variations of chlorophyll content.6. The grain-filling rate of the whole fruit stage, the period from anthesis to doughingtime and the period from doughing time to mature time was1.1094,1.4661and0.2344g/(1000kernels·d);19.3%,16.6%and10.9%higher than the normal senescing sequence wheatrespectively, which revealed its high yield characteristics.The differences in physiological characters between the inverted senescing sequencewheat and the normal senescing sequence wheat is significant to reveal the laws of invertedsenescence, and to provide the theoretical reference in enriching the senescence of wheat.