[Changes of grain yield and agronomic traits during millet variety replacements in northern Shaanxi, China.] / 陕北谷子品种更替过程中产量及农艺性状的演变.

A field trial was conducted to examine the differences of grain yield and agronomic characters of six millet (Setaria italica) varieties in Yulin, Shaanxi during 2018-2019 growing seasons. Those varieties were planted in northern Shaanxi in different decades (1960s-1970s, 1980s-1990s, 2000s-2010s). The results showed that the grain yield of millet varieties exhibited an increasing trend across all the decades. The average yield of varieties bred from 2000s to 2010s were 0.46 (2018) and 0.66 kg·m-2 (2019), respectively. The yield increased significantly by 22%-53% compared with the bred before 2000s. Changes of plant height, panicle weight, leaf weight and stem weight were similar to that of yield, while one-thousand kernel weight and spike length were relatively stable which did not change significantly across the decades. The flag leaf width increased significantly with the variety replacements. There was a significant correlation between panicle weight, stem weight, leaf weight, plant height and grain yield, respectively. Results of principal component analysis showed that millet varieties bred from 2000s to 2010s had greater advantages. In the process of millet cultivars replacement in northern Shaanxi, yield per unit area was mainly increased through the improvement of plant height and spike weight. In the future, we should focus on the improvement of plant height, spike weight, stem weight, and leaf weight, especially the exploration of the optimal plant height suitable for mechanical harvesting.

[Application of pressure probe techniques in studies of plant water relations].

This review introduces the pressure probe technique that was originally designed to detect the turgor of a giant algal cell, then adapted to measure the turgor and other water-relations parameters of higher plants, and now has developed into a diverse tool on researches of plant physiology and eco-physiology. This technique can be used to measure in situ the permeability of cell membranes to water and solutes at the resolution of single cells, and hence is a useful tool to study function and regulation of water channels (aquaporins) of intact plant cells. The recently developed xylem-pressure probe technique is the only way to directly measure the negative pressure in xylem conduits. In this review we introduce the basic principles and the theoretical backgrounds underlying the pressure probe. Finally some important achievements and applications of the pressure probe in studies of plant water relations are reviewed and discussed.

[Expression of ZmPIP1 subgroup genes in maize roots under water shortage].

To investigate the role of ZmPIP1-1 and ZmPIP1-2 in water uptake of roots and drought resistance of crops, semi-quantitative PCR was used to examine the expression of ZmPIP1-1 and ZmPIP1-2 in root systems of different maize genotypes under water deficit. These genotypes showed different resistance to water shortage under field conditions. The reference gene to target genes was tubulin. Maize seedlings were grown by hydroponics in a growth chamber. Water deficit was imposed on the seedlings with PEG-6000. The result showed that ZmPIP1-1 was up-regulated under water deficit in root systems of plants of the filial generation 'Hudan 4' and the mother line 'Tiansi', which were resistant to water shortage, but there was no noticeable up-regulation of ZmPIP1-1 in the root systems of the father line '803', which was sensitive to water deprivation. The result also showed that the extent of up-regulation was positively correlated with drought resistance of maize (Fig.3). On the other hand, the expression of ZmPIP1-1 showed different degrees of tendency after different duration of water stress in the root systems of the maize seedlings of different genotypes. The result showed that ZmPIP1-2 was identically expressed in three different species of maize and under different water conditions. The results support the theory that the intercellular water transport contributes to increased water uptake in root systems under water deficit by up-regulating the number of some kinds of aquaporins. The increases amount of transcripts of aquaporins is positively correlated to drought resistance of plant varieties. But not all kinds of number of aquaporins is up-regulated during water shortage, some kinds of aquaporins are identically expressed under water deficit conditions and well watered conditions.