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Net assimilation rate dynamics of cotton during the growth stages under zinc element regulation

Zhi Jinhu, Zhai Yunlong, Wu Jing, Xu Chongzhi, Wand Desheng

It is well known that zinc can promote plant growth and enhance its resistance, but the influence of zinc on cotton net assimilation rate has not been reported. The change rule of cotton’s net assimilation rate under the application of zinc element is studied by means of field trial, which provides a scientific basis for reasonable application of zinc fertilizer for cotton. The results show that cotton net assimilation rate (NAR) is associated with growth period and consumption of zinc. NAR shows a tendency of rising first and then decreasing with the growing period; the maximum NAR appears during bud stage ~ flowering stage (LH). NAR shows an obvious rising tendency with the increase of zinc dosage during the earlier growth stage (seedling stage ~ full blossom stage), and the NAR is obviously decreased with the increase of zinc dosage during the middle and later growth stage (flowering stage ~ boll opening stage). After the later growth stage (boll-forming stage), NAR is not obviously responded to zinc. And the NAR in the experiment group at all stages is lower than that of the control group (no zinc treatment). During full blossom stage ~ boll-forming stage, zinc dosage and NAR are significantly associated in the linear relationship, exponential relationship and quadratic curve relationship; Quadratic curve of one variable is more significant (R2 = 0.7349). Cotton production firstly raises and then falls with the increase of zinc consumption. When ZnSO4 • 7 H2O is 20 kg/hm2, cotton production reaches the highest