叶片的光照异质性可引起其结构与生理功能的异质性。对于单个叶片来说，其叶片不同部位的受光往往存在较大的异质性。然而，单个叶片不同部位的异质性光照如何影响其所在部位的结构与生理功能尚未明确。本研究以具有叶片翘曲特性的海岛棉为材料，开展田间原位测定和遮荫模拟试验。田间试验测定了东西南北四个方向叶片主脉两侧的光合特性和形态结构。研究表明，各方向叶片主脉两侧的光合能力的差异与光照日辐射量（DPI）密切相关。这表明叶片主脉两侧的光合异质性受其自身的光照日辐射量的影响。进一步通过叶片局部遮荫模拟试验验证了这一结论。同时，局部遮荫叶片未遮荫侧的光合能力和叶片厚度等显著低于未遮荫叶片。因此，单个叶片的不同部位间存在光合性能的系统调控。

To cope with a highly heterogeneous light environment, photosynthesis in plants can be regulated systemically.  Currently, the majority of studies are carried out with various plants during the vegetative growth period.  As the reproductive sink improves photosynthesis, we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field.  Therefore, changes of light intensity within canopy, chlorophyll content, gas exchange, and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities.  In this study, a high planting density of maize drastically reduced the light intensities in the lower canopy, and increased the difference in vertical light distribution within the canopy.  With the increase of vertical heterogeneity, chlorophyll content, light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf (EL) and the fourth leaf below the ear (FLBE) were decreased gradually, and the ranges of declines in these parameters were larger at FLBE than those at EL.  Leaves in the lower canopy were shaded artificially to further test these results.  Partial shading (PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE.  Removing the tassel and top leaves (RTL) not only improved the vertical light distribution within the canopy, but also reduced the differences in photosynthetic characteristics between the two leaves.  Taken together, these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment; slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Machine harvesting increases the foreign matter content of seed cotton.  Excessive cleaning causes fiber damage and economic loss.  Most trading companies in the Xinjiang Uygur Autonomous Region, China have indicated reluctance to use machine-harvested cotton.  The first objective was to determine how the fiber quality was affected by the ginning and lint cleaning and how the fiber damage during levels of lint cleaning changed. The second objective was to determine the optimum number of lint cleaners for machine-harvested cotton based on fiber damage.  Cotton samples were collected from 13 fields and processed in seven ginneries between 2013 and 2015.  The results indicated that ginning and lint cleaning didn’t have significant effect on fiber strength and significantly affected both fiber length and short fiber index.  Fiber length was reduced by more than 1.00 mm from six of 13 fields after lint cleaning, then the damage rate on short fiber index from 11 of 13 fields was more than 20%.  The third lint cleaning caused great fiber damage, reducing fiber length by 0.35 mm and increasing short fiber index by 0.65%.  So, the lint should be cleaned by one lint cleaner in the Xinjiang, however, the stage of lint cleaning was sometimes omitted when the foreign matter content of lint was little.

Increasing plant density is an effective way to enhance maize yield, but often increases lodging rate and severity, significantly elevating the risk and cost of maize production.  Therefore, lodging is a major factor restricting future increases in maize yield through high-density planting.  This paper reviewed previous research on the relationships between maize lodging rate and plant morphology, mechanical strength of stalks, anatomical and biochemical characteristics of stalks, root characteristics, damage from pests and diseases, environmental factors, and genomic characteristics.  The effects of planting density on these factors and explored possible ways to improve lodging resistance were also analyzed in this paper.  The results provide a basis for future research on increasing maize lodging resistance under high-density planting conditions and can be used to develop maize cultivation practices and lodging-resistant maize cultivars.

The objectives of this study were to determine how the distribution of photosynthetically active radiation (PAR) in a maize canopy affected basal internode strength and stalk lodging.  The distributions of PAR within the canopies of two maize cultivars (Zhongdan 909 and Xinyu 41) were altered by removing whole leaves or half leaves in different canopy layers.  The results showed that removing whole leaves or half leaves above the three-ear-leaves (R_AE and R_AE/2) at flowering significantly increased PAR at the ear and interception of PAR (IPAR) from the ear to middle of the ear and soil surface.  These changes increased the structural carbohydrate content and rind penetration strength (RPS) of the third basal internode by 5.4–11.6% and reduced lodging by 4.2–7.8%.  Removal of the first three leaves below the three-ear-leaves (R_BE) before flowering significantly reduced IPAR from the ear to half way below the ear.  This reduced the structural carbohydrate content and the RPS of the third basal internode by 9.1–17.4% and increased lodging by 7.0–11.2%.  Removal of the three lowest green leaves (R_B) in the canopy before flowering increased PAR at the bottom of the canopy, but had no effect on the structural carbohydrate content of the basal internode, the RPS, and the lodging rate.  Overall, the results indicated that the key factors affecting the basal internode strength formation and lodging were PAR at the ear and IPAR from the ear to halfway below the ear.  Increasing PAR at the ear and IPAR from the ear to halfway below the ear could enhance lodging resistance by increasing the structural carbohydrate content and mechanical strength of the basal internode

   Gas exchange and chlorophyll a fluorescence were measured to study the effects of soil water deficit (75, 60 and 45% of field capacity, FC) on the photosynthetic activity of drip-irrigated cotton under field conditions. At light intensities above 1 200 µmol m⁻² s⁻¹, leaf net photosynthetic rate (P_n) at 60 and 45% FC was 0.75 and 0.45 times respectively than that of 75% FC. The chlorophyll content, leaf water potential and yield decreased as soil water deficit decreased. Fiber length was significantly lower at 45% FC than at 75% FC. The actual quantum yield of the photosystem II (PSII) primary photochemistry and the photochemical quenching were significantly greater at 60% FC than at 75% FC. The electron transport rate and non-photochemical quenching at 45% FC were 0.91 and 1.29 times than those at 75% FC, respectively. The amplitudes of the K- and L-bands were higher at 45% FC than at 60% FC. As soil water content decreased, active PSII reaction centers per chlorophyll decreased, functional PSII antenna size increased, and energetic connectivity between PSII units decreased. Electron flow from plastoquinol to the PSI end electron acceptors was significantly lower at 45% FC than at 75% FC. Similar to the effect on leaf P_n, water deficit reduced the performance index (PI_{ABS, total}) in the dark-adapted state. These results suggest that (i) the effect of mild water deficit on photosystem activity was mainly related to processes between plastoquinol and the PSI end electron acceptors, (ii) PSI end electron acceptors were only affected at moderate water deficit, and (iii) PI_{ABS, total} can reliably indicate the effect of water deficit on the energy supply for cotton metabolism.

Water deficit is one of the most important causes of decreased yield in cultivated plants. Non-foliar green organs in cotton play an important role in yield formation at the late growth stage. Although better photosynthetic performance was observed in a non-foliar organ (bract) compared with leaves under water deficit. However, the physiological response of each organ in cotton to water deficit has not been comprehensively studied in relation to the water status and photosynthesis characteristics. We studied the maintenance of water status of each organ in cotton by measuring their relative water content, proline content and stomatal characteristics. Water deficit significantly decreased the surface area of each organ, but to a lesser extent in non-foliar organs. Our results showed that the relative contribution of biomass accumulation of non-foliar organs increased under water deficit. Non-foliar organs (bracts and capsule wall) showed less ontogenetic decrease in O2 evolution capacity and in RuBPC activity (per dry weight) as well as better antioxidant systems than leaves at various days after anthesis. We conclude that the photosynthesis from non-foliar organs is important for increasing cotton yield especially under water deficit conditions.

Though bract and capsule wall of boll in cotton (Gossypium hirsutum L.) have different photosynthetic capacities, the features of photosystem II (PS II) in these organs are scarce. In this paper, chlorophyll a fl uorescence emission was measured to investigate the difference in the photosynthetic apparatus of dark-acclimated (JIP-test) and light-acclimated (light-saturation pulse method) bract and capsule wall. Compared with leaves, the oxygen evolving system of non-foliar organs had lower effi ciency. The pool size of PS II electron acceptor of non-foliar organs was small, and the photochemical activity of leaves was higher than that of the bract and capsule wall. In regard to the photosystem I (PS I) electron acceptor side, the pool size of end electron acceptors of leaves was larger, and the quantum yield of electron transport from QA (PS II primary plastoquinone acceptor) further than the PS I electron acceptors of leaves was higher than that of bract and capsule wall. In all green organs, the actual quantum yield of photochemistry decreased with light. The thermal dissipation fraction of light absorbed by the PS II antennae was the highest in bract and the lowest in capsule wall relative to leaves. Compared with leaves, capsule wall was characterized by less constitutive thermal dissipation and via dissipation as fl uorescence emission. These results suggested that lower PS II photochemical activity in non-foliar organs may be result from limitations at the donor side of PS II and the acceptor sides of both photosystems.